Garden Ecology
Transcript of Garden Ecology
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Study Guide
Garden EcologyBy
Matt Brooks
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About the Authors
Matt Brooks received a Bachelor of Landscape Architecture degree
from the University of Illinois and a Master of Landscape Architecture
degree from the University of Minnesota. He then spent several
years working in the Chicago area with various landscape architec-
tural and design/building firms. In these positions, Matts primary
responsibilities included landscape design and sales and project
management of commercial-, institutional-, and residential-scale
projects. Soon after moving to Minnesota in 1997, Matt accepted a
teaching position with Dakota County Technical College, where he
teaches courses in landscape design, computer-aided design (CAD),
and woody plant identification. In addition to teaching, Matt is
president of Brooks Design Group Inc., a landscape design and
construction services consulting company. Matts work has appeared
in Better Homes and Gardens, in Northern Gardener, and most
recently at the University of Minnesota Landscape Arboretum. Matt
is a member of the Minnesota Nursery and Landscape Association,
where he sits on the Environmental Concerns Committee. He is
also a member of the American Society of Landscape Architects.
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INSTRUCTIONS TO STUDENTS 1
LESSON ASSIGNMENTS 7
LESSON 1: THE FUNDAMENTALS OF PLANT
AND SOIL SCIENCE 9
LESSON 2: GARDEN ECOLOGY 27
LESSON 3: THE FUNDAMENTALS OF
COMMON-SENSE PEST CONTROL 49
SELF-CHECK ANSWERS 73
ACHIEVEMENT REVIEW ANSWERS 80
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INTRODUCTION
Landscaping can be defined as the art and science of altering
the visible features of the land, which results in the creation
of beautiful and functional outdoor environments. Alterations
through the incorporation of living elements such as trees,
shrubs, and flowers; natural elements including landforms,
stones, or water; and built elements such as garden struc-
tures, walls, and fences rely on the artistic eye. On the other
hand, an understanding of the environment, the natural
processes that occur in shaping it, and the intricate relation-
ships that exist among the living organisms that dwell there
form the scientific basis of landscaping. Ecology is the term
used to describe the scientific study of the relationships that
occur between living organisms and between living organisms
and their environment. This course presents the concepts of
garden ecology and examines both the living and nonliving
natural components that form the framework of gardens and
the larger landscape.
This course includes three lessons. Heres a summary of
what youll study in each one:
In Lesson 1, The Fundamentals of Plant and Soil
Science, youll gain a basic understanding of plants and
soils. Youll learn about plant structure, the function of
various plant parts, and the growth processes inherent
in green plants. Youll also be introduced to the methods
and terms used in identifying plants, the scientific system
for naming plants, the reproductive process in plants,
and the role plant regulators play in the production of
plants. Last, youll study the vital role soils play in the
health of plants, the way soils are formed, differences in
soil structure, and the chemical properties of soils.
Lesson 2, Garden Ecology, builds upon the fundamental
information learned in Lesson 1 through a more holistic
approach that introduces you to the science of ecology as
it applies to the smaller-scale garden or residential land-
scape. While some of the information in this lesson will
be familiar to you from your readings in Lesson 1, this
additional perspective on the fundamentals will prove
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quite beneficial in a deeper understanding of the subject
matter. In this lesson, youll learn to appreciate not only
the individual parts that make up the garden or land-
scape but also the intricate interactions among the
various parts that make it a highly functioning ecosystem.
In Lesson 3, The Fundamentals of Common Sense Pest
Control, youll learn about the various natural controls
that keep pest populations in check. Youll also be intro-
duced to the concept of integrated pest management (IPM)
and the treatment strategies and tactics utilized in man-
aging pests in the garden and landscape. Youll learn
how to identify and appreciate the services of beneficial
insects and other organisms in controlling pest popula-
tions. Next you'll learn how to choose the right chemical
and microbial tools as well as other organic and inor-
ganic tools used in common sense pest control. And
lastly, this lesson will introduce you to the new frontier
of microbials, pheromones, and insect growth regulators
used in pest control today.
These three lessons are further divided into several individual
assignments that typically correspond to one, sometimes two,
chapters in one of your textbooks. At the end of each assign-
ment, youll complete a self-check to determine how well
youve learned the material youve just studied. The answers to
the self-checks are at the back of this study guide. At the
end of each lesson, you must complete an examination.
OBJECTIVES
When you complete this course, youll be able to
Describe the relationships among landscapes, plants,
and the soils and other living organisms that make up
the ecology of our gardens
List the important roles plants play in our lives and
Earths ecosystem
List the parts typical of higher green plants and explain
their functions
Instructions to Students2
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Describe the process of photosynthesis and the role it
plays in sustaining all life on Earth
Summarize the natural classification system for the
plant kingdom
Describe the environmental factors that affect plant
growth
Identify the parts of plants that are used in plant
identification
Explain the important role soils play in our lives and
Earths ecosystem
Describe the various components that make up soils and
explain how and why soils differ
Define the term soil structure and list the factors that
influence various soil structures
Describe the different types of plant growth regulators
and their effects on plants
Explain the various forms of plant reproduction and list
the parts of a plant involved in the process
Identify the most common methods used in plant
propagation
Identify the major causes of injury to plants
Identify natural pest controls
List the principles of common sense pest control
Explain the concept of integrated pest management (IPM)
List the different types of beneficial insects and organ-
isms used in IPM
Describe the various organic and inorganic tools used
in IPM
Instructions to Students 3
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COURSE MATERIALS
This course includes the following materials:
1. This study guide, which contains an introduction to your
course, plus
A lesson assignments page with a schedule of study
assignments
Introductions to lessons and assignments, which
emphasize the main points in the textbooks
Self-checks and answers to help you assess your
understanding of the material
Answers to the Achievement Review features at the
end of each chapter in Ornamental Horticulture
2. Your course textbooks, Ornamental Horticulture: Science,
Operations, & Management; Ecology for Gardeners; and
The Gardeners Guide to Common-Sense Pest Control,
which contain the assigned reading materials
YOUR TEXTBOOKS
This course includes three textbooks: Ornamental
Horticulture: Science, Operations, & Management; Ecology for
Gardeners; and The Gardeners Guide to Common-Sense Pest
Control. These books contain the study material on which the
self-checks and examinations are based. You should become
familiar with your textbooks prior to the beginning of your
studies. Skim through the contents pages of each book. These
pages will give you a preview of the chapters in each text-
book, as well as a listing of topics specific to each chapter.
Note: Only selected chapters in your textbooks are required
reading for this course.
Each chapter in Ornamental Horticulture begins with a list
of objectives and key terms. Read these objectives prior to
beginning your studies, as theyll prepare you for what youll
be learning. While reading, pay particular attention to the key
terms that are highlighted in bold type throughout the
Instructions to Students4
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chapters. At the end of each chapter is a feature called
Achievement Review. You can use these questions to review
what youve just read and studied in a chapter. The answers
to these exercises are at the back of this study guide. Starting
on page 627 are a number of appendices, which contain use-
ful information such as professional trade organizations,
selected readings for further studies in ornamental horticul-
ture, and examples of plant diseases and insect injuries. A
glossary of all of the key terms listed in your book begins on
page 649. You may find this glossary useful when reviewing
for exams. Finally, an index begins on page 661. Use this
feature to locate specific topics in the textbook.
Your second textbook, Ecology for Gardeners, is broken down
into six chapters. It too contains a glossary of terms that
begins on page 280, a list of books for further reading on
pages 290291, an index of common and scientific names
starting on page 292, and a subject index starting on page
320. In the middle of the textbook (between pages 96 and 97)
are numbered photo plates, which are referenced throughout
the book. The vast amount of information presented in this
book may at times overwhelm you with all of the scientific
names and terminology, and thats OK. Heres a suggestion to
help in your studying: First read through each chapter to get
an overall idea of the material presented, and then go back
with a highlighter and mark the major terms and concepts in
preparation for your exam reviews.
Your third textbook, The Gardeners Guide to Common-Sense
Pest Control, is broken down into two parts. For this study
guide youll be assigned readings from the first half of the
book and in a later study guide youll be referencing the sec-
ond half of the book. In addition to the assigned readings, you
should read the Preface and Introduction and pages 1316
on sustainable landscape gardening. While not included as
part of your assigned readings, these pages contain insightful
information from the authors and set the tone for the content
presented in the rest of the book. Starting on page 374 is the
Afterword with some closing thoughts by the author followed
by a sample case study that uses the city of San Francisco's
IPM program as an example to highlight the application of the
principles and practices presented in this book. Starting on
page 378 is a reference section with suggestions for further
Instructions to Students 5
Note: When referencingthis textbook in yourassignments the titlewill be abbreviated toPest Control.
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reading on particular subjects, listed according to book chap-
ter. Lastly, starting on page 383 is the index, which youll find
helpful when looking up information on a particular topic.
A STUDY PLAN
The following is a recommended procedure for successfully
completing this course while receiving the maximum benefit
from your studies:
1. Read the introduction to each assignment and make
note of assigned readings in both the study guide and
textbook.
2. When applicable, read the chapter objectives at the
beginning of assigned textbook readings; then read the
material for a general understanding of subject matter.
3. Go back and reread assigned materials, highlighting or
underlining key concepts and passages to help you
remember essential information.
4. When you feel you have an understanding of the assigned
reading, take the self-check at the end of the assignment
in your study guide. Compare your answers with those
given at the end of this guide. If you had any incorrect
answers, go back and review the assigned reading mate-
rial. This review will reinforce your understanding of the
material. The self-checks are designed to reveal weak
points that you need to review. Dont send the self-check
answers to the school. Theyre for you to evaluate your
understanding of the material.
5. Complete each assignment in this way.
6. When you feel you understand all of the material in a
lesson, complete the examination for that lesson.
7. Repeat this procedure for each lesson.
Remember: At any time, you can email your instructor for
information regarding the materials. The instructor can pro-
vide you with answers to any questions you may have about
the course or your study materials.
Youre now ready to begin Lesson 1. Good luck!
Instructions to Students6
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Lesson 1: Fundamentals of Plant and Soil Science
For: Read in the Read in the textbook
study guide: Ornamental Horticulture:
Assignment 1 Pages 1011 Chapter 1
Assignment 2 Pages 1315 Chapter 2
Assignment 3 Pages 1719 Chapter 3
Assignment 4 Pages 2122 Chapter 4
Assignment 5 Pages 2425 Chapter 5
Examination 102835 Material in Lesson 1
Lesson 2: Garden Ecology
For: Read in the Read in the textbook
study guide: Ecology for Gardeners:
Assignment 6 Page 29 Chapter 1
Assignment 7 Pages 3132 Chapter 2
Assignment 8 Pages 3436 Chapter 3
Assignment 9 Pages 3739 Chapter 4
Assignment 10 Pages 4143 Chapter 5
Assignment 11 Pages 4547 Chapter 6
Examination 102836 Material in Lesson 2
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Lesson 3: Fundamentals of Common Sense Pest Management
For: Read in the Read in
study guide: the textbook:
Assignment 12 Pages 5052 Chapter 6 in Ornamental
Horticulture
Assignment 13 Pages 5456 Chapter 2 in Pest Control
Assignment 14 Pages 5759 Chapters 34 in Pest
Control
Assignment 15 Pages 6162 Chapter 5 in Pest Control
Assignment 16 Pages 6466 Chapters 67 in Pest
Control
Assignment 17 Pages 6870 Chapter 8 in Pest Control
Examination 102837 Material in Lesson 3
Lesson Assignments8
Note: To access and complete any of the examinations for this studyguide, click on the appropriate Take Exam icon on your My Coursespage. You should not have to enter the examination numbers. Thesenumbers are for reference only if you have reason to contact StudentServices.
Remember to regularlycheck My Courseson your studenthomepage. Yourinstructor may postadditional resourcesthat you can accessto enhance yourlearning experience.
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Fundamentals of Plant and Soil ScienceThe purpose of Lesson 1 is to provide you with a basic under-
standing of plants and the soils they depend upon for growth
and reproduction. This lesson includes five assignments that
cover Chapters 15 in the textbook Ornamental Horticulture.
Assignment 1 covers plant morphology (structure), plant
nomenclature, plant processes, and requirements for plant
growth. Assignment 2 focuses on the terminology and meth-
ods used in describing and identifying plants. Assignment 3
discusses the properties of soil and its importance in plant
health. Assignment 4 explains how and why growth regula-
tors are used, and finally, Assignment 5 describes the many
ways in which plants naturally reproduce and the methods
used by humans in propagating plants.
OBJECTIVES
When you complete this lesson, youll be able to
Summarize the important roles plants play in peoples
lives and in Earths ecosystem
List the parts typical of higher green plants and the
functions of these parts
Describe the process of photosynthesis and the role it
plays in sustaining all life on Earth
Describe the natural classification system for the plant
kingdom
Describe the environmental factors that can affect plant
growth
Identify the parts of plants that are used in plant
identification
Explain the important role soils play in peoples lives and
in Earths ecosystem
Characterize the various components that make up soils
and indicate how and why soils differ
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Garden Ecology10
Define the term soil structure and list the factors that
influence various soil structures
Identify the different types of plant growth regulators and
describe their effects on plants
Explain the various forms of plant reproduction and
identify the parts of a plant involved in the process
Describe the most common methods used in plant
propagation
ASSIGNMENT 1: THE GREEN PLANT
Read the following material. Then read Chapter 1 (pages 124)
in your textbook, Ornamental Horticulture.
Green plants are amazing machinesthe only organisms
capable of manufacturing their own food. Through a process
known as photosynthesis, plants use the raw materials of
sunlight, soil, air, and water to produce the food they need.
In addition, plants are the source of some important nutri-
tional needs of humans. For example, the leaves of some
plants, such as spinach and kale, are loaded with vitamins
and minerals, while tea leaves are brewed into a beverage
rich in antioxidants that protect the human body from ill
health. Other plant partssuch as the roots of carrot and
potato plants; the fleshy fruits of apple and orange trees;
nuts from trees and shrubs; and most notably, the grains
produced by corn, rice, and wheatare sources of nutrition.
Textbook Note
On page 16 of your textbook, the chemical equation for photo -synthesis should read as follows:
6CO2 + 12H2O C6H12O6 + 6O2 + 6H2O
The equation in the textbook is missing the C immediately after the yield symbol.
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Lesson 1 11
Even the ground beef in your hamburger and the eggs in
your omelet depend on plants as the nutritional source for
the cow and chicken that produce the meat and eggs.
Plants also provide raw materials used in the manufacture
of products that bring comfort to peoples lives. For example,
plants are sources for the building materials used in the con-
struction of homes that shelter people from the elements;
theyre the basis of some fibers used in making clothing that
keeps people warm and dry. Other uses for the woody parts
of a plant include the manufacture of paper products that
allow people to communicate the written word through books
and newspapers, to package and ship goods across the
country, and to have a hot pizza delivered to their front
doors. And how would the pizza get delivered if not for the
fossil fuels made possible by plants that covered Earth mil-
lions of years ago?
As a student in the Landscape Technology program, youll
learn to appreciate plants in another way as wellthat is,
for their aesthetic and functional roles in gardens and land-
scapes. To effectively use plants in creating beautiful and
functional outdoor spaces, you must have a basic under-
standing of plants. The purpose of this assignment is to help
you gain that understanding by introducing you to plant
structure, the terminology used in describing the parts of a
plant, the process of plant growth, and the requirements for
proper growth. Youll also be introduced to the system of
classifying and naming plants.
Now its time to complete Self-Check 1 to help you review
what youve just studied and determine how well you under-
stood the material. In addition, you may wish to complete the
Achievement Review on pages 2427 of the textbook. The
answers to this review can be found at the back of this study
guide.
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Garden Ecology12
Self-Check 1
At the end of each section of Garden Ecology, youll be asked to pause and check
your understanding of what youve just read by completing a Self-Check exercise.
Answering these questions will help you review what youve studied so far. Please
complete Self-Check 1 now.
Note: You may also wish to use the reviews at the end of the chapters in your textbook.
The answers to these reviews are also found at the end of this study guide.
Match each term in the left column below with its definition in the right column.
______ 1. Photosynthesis
______ 2. Chlorophyll
______ 3. Oxygen
______ 4. Flower
______ 5. Transpiration
______ 6. Taxonomy
______ 7. Plant nomenclature
______ 8. Latin
______ 9. Phototropism
______ 10. Cell walls
Check your answers with those on page 73.
a. The language used in the scientific/botanical naming of plants
b. A gaseous byproduct of photosynthesis required forhuman survival
c. The structures present in plant cells that make themdifferent from animal cells
d. The process of converting energy from solar to chemi-cal form through the manufacture of sugar
e. The scientific study of plant classification
f. The green pigment needed by plants to capture thesuns energy
g. The process through which water vapor is releasedthrough pore-like openings in the leaf
h. The system for naming plants
i. The plant structure containing both pistil and stamen
j. The term used to describe a plants bending growth inresponse to a light source
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Lesson 1 13
ASSIGNMENT 2: DESCRIBINGAND IDENTIFYING PLANTS
Read the following material. Then read Chapter 2, pages 2844,
in your textbook, Ornamental Horticulture.
Plants are the primary materials that landscape professionals
use to create attractive gardens and landscapes. The key to
successfully using plants in landscapes is the ability to
describe and identify plants. The problem is that there are
many different methods of describing plants.
One method uses plants common names. This method is
complicated by the fact that one plant may go by several
different names. For example, many people use the term
burning bush to describe a particular shrub that turns
bright red in autumn. Others, however, refer to this
same bush as the winged euonymus. You can see how
using plants common names may lead to confusion.
Another method uses the scientific names of plants that
you learned about in Chapter 1. This method was devel-
oped by Karl von Linne, the father of taxonomy. In this
system, each plant has its own unique scientific name
that consists of two parts, the genus and species.
Although this system eliminates confusion among
scientists and professionals familiar with this language,
confusion persists among the general population, who
usually refer to plants by their common names.
As a landscape professional, you should be knowledgeable in
both the scientific and common names of plants. While over-
whelming at first, continued practice and learning through
repeated use will result in the mastering of this new language
that separates landscape professionals from hobbyists.
In addition to their scientific and common names, plants may
also be identified or named in other ways. Here are a few dis-
cussed by your textbook in Chapter 2:
Horticultural descriptions of plants. Because the botanical
classification and scientific naming of plants is very spe-
cific, it reduces confusion. However, a less complicated
method with more generic terms is often used to refer to
Because a scientificname consists of twoparts, its called a binomial.
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Garden Ecology14
larger groups of plants that share like physical character-
istics. For example, the term deciduous refers to plants
that shed their leaves annually, while the term evergreen
refers to plants that retain them for several years. Such
broad categories are useful among professionals in the
field of ornamental horticulture. Your textbook lists and
describes these categories of plants in greater detail on
pages 2931.
Description based on temperature tolerance. Plants are
also categorized according to their tolerances of high
and low air temperatures. While water, sunlight, and
soil nutrients are contributing factors in a plants ability
to survive, temperature extremes are of paramount
importance in determining the suitability of a plant
to a particular climatic zone. The term plant hardiness
describes this ability for plant survival based on air tem-
perature. Hardiness zones have been devised to indicate
a plants suitability to different geographic regions of the
globe. Both heat and cold hardiness zones are displayed
on maps that serve as a general guide to proper plant
selection based on this limiting factor. (Page 32 in your
textbook illustrates a hardiness zone map of North
America.) Specific site features, such as a south-facing
wall or the proximity to large bodies of water or to a large
city, can influence air temperatures on a smaller scale.
Although such features may not appear on the hardiness
zone maps, they can have an influence on the selection
of appropriate plants for a specific location.
Visual descriptions of plants. In the final pages of
Chapter 2, youll examine the physical features (leaves,
twigs, and fruit) that aid in plant identification. The abil-
ity to correctly identify plants is a skill vital to landscape
The website for the U.S. Department of Agriculture includes an inter-active hardiness zone map. To locate this map, type departmentagriculture hardiness zone map into your browsers search box.
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Lesson 1 15
professionals. To obtain this skill, you must acquire
a basic familiarity with the terms used in plant
identification.
While the vast amount of information presented in your text-
book can be rather intimidating at first, over time these plant
features and the terms used to describe them will become
second nature to you. In the meantime, when an unfamiliar
term appears in the description of a plant, take the time to
look it up in the glossary or index of your book.
Now, take a moment to complete Self-Check 2 and the
Achievement Review on pages 4446 of the textbook to help
you review what youve just studied. Once you understand
the material, move on to Assignment 3.
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Garden Ecology16
Self-Check 2
Match each term in the left column below with its definition in the right column.
______ 1. Linnaeus
______ 2. Herbaceous
______ 3. Perennial
______ 4. Hardiness
______ 5. Alternate
______ 6. Chambered
______ 7. Raceme
______ 8. Pome
______ 9. Lobed
______ 10. Naked
Check your answers with those on page 73.
a. A term used to describe a type of fruit
b. A term used to describe a bud lacking bud scales
c. The father of taxonomy
d. A term used to describe the structure of a flower
e. A plant that doesnt die after flowering; a plant that can survive the cold in a dormant state
f. A term used to describe the margin of a leaf blade
g. A term used to describe the arrangement of leaves along a plant stem or twig
h. The term used to describe a plant lacking a hard bark coveringon its stems
i. A term used to describe the pith or inside of a stem or twig
j. The term used to describe a plants tolerances based on tem-perature extremes
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Lesson 1 17
ASSIGNMENT 3: THE SOIL
Read the following material. Then read Chapter 3, pages 4764,
in your textbook, Ornamental Horticulture.
What Is Soil?
To most people, soil, or dirt, is a nuisance that gets tracked
into the house. To a farmer or horticulturist, however, soil is
the life-giving medium that anchors and nourishes the plants
that are the lifeblood of their professions.
If you want to become a successful landscape professional,
you must have an understanding of the complexities of soil
and its influence on the health of plants. In this assignment,
youll be introduced to physical components that make up
soils and how soils differ. Youll also study the chemical ele-
ments essential to plant growth and the processes through
which these elements become available for use by plants.
The primary components of soil include mineral particles
(weathered rock in the form of gravel, sand, silt, and clay),
organic matter, air, and water. Generally, the ratio of these
elements is as follows:
Mineral particles form the bulk of most soils at roughly
45%.
Organic matter contributes only 5%. Of this 5%, approxi-
mately 80% is in the form of humus, with the remaining
20% equally split between roots and living organisms.
Air and water account for approximately 25% each.
Soil Separates and Soil Texture
The size and proportion of the mineral particles in soil deter-
mine the classification of that soil. These particles are called
soil separates. Since most soils contain a percentage of sand,
silt, and clay, these three separates are used to determine the
classification of soil.
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Garden Ecology18
Page 52 in your textbook illustrates the soil texture triangle
developed by the U.S. Department of Agriculture. This triangle
is used to classify the texture class of a soil. If you know the
percentage of two of the three separates (sand, silt, and clay),
you can determine the classification of the texture of a soil.
Heres how it works: The sides of the soil texture triangle are
scaled for the percentages of sand, silt, and clay. Clay per-
centages are read from left to right across the triangle. Silt is
read from the upper right to lower left. And sand is read from
lower right toward the upper left portion of the triangle. The
boundaries of the different soil texture classes are highlighted
in bold dashed lines.
The intersection of the three particle sizes on the triangle
gives the texture class. For instance, suppose you have a soil
with 20% clay, 60% silt, and 20% sand. Heres how to use
the triangle to determine the soil texture.
1. Find 20 along the side for clay, and draw a line from left
to right from the 20.
2. Find 60 along the line for silt, and draw a line from the
60 down and to the left.
3. Find 20 along the line for sand, and draw a line from the
20 up and to the left.
4. Identify the section in which these three lines intersect.
In this case the soil is silty loam.
Note: In this example, we used the percentages for all three
separates. However, if you know only two of the three, you
can still use the triangle. The intersection of the two lines will
give you the type of soil.
Soil Structure and Organic Material
As youve just learned, the main mineral components of soil
are sand, silt, and clay particles. You also learned that
different types of soil contain different amounts of these
components. In addition, the arrangement of soil particles,
called soil structure, influences the makeup of soil. According
to the website for the U.S. Department of Agriculture, soil
structure is the combination or arrangement of primary soil
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Lesson 1 19
particles into aggregates [larger particles of soil]. . . Soil
structure affects water and air movement through soil,
greatly influencing soils ability to sustain life and perform
other vital soil functions.
In a nutshell, soil structure, or the arrangement of soil parti-
cles, influences the soils ability to support plant life.
Soil Acidity and Alkalinity
There are 17 elements essential for plant growth, including
carbon, nitrogen, calcium, magnesium, iron, zinc, copper,
and others. Of these 17 elements, soil provides all but three
of them. Only carbon, hydrogen, and oxygen are obtained by
most plants from sources other than the soil. These elements
determine the pH number, which indicates the acidity, alka-
linity, or neutrality of soil. The pH number of a soil affects
the capacity of that particular soil to make essential elements
available for absorption by plant roots. Just as air tempera-
ture extremes can be a limiting factor in making plant
selections, so too can the pH of a soil. That is, certain plants
require a specific pH for optimal growth and even survival.
While its possible to modify the pH of a soil through organic
and/or chemical means, its usually best to select plants
according to existing soil conditions.
Pedology, the study of soils, is a science as complex as
botany, the study of plants, or zoology, the study of animals.
You would need years of study to become an expert in the
field. The purpose of this assignment is to introduce you to
properties of soil and the importance soils play in the health
of plantsnot to make you an expert. Future assignments in
this study guide expand on the knowledge gained here, allow-
ing you the ability to appreciate the vital role soils play in a
healthy landscape.
Now, take a moment to complete Self-Check 3 and the
Achievement Review on pages 6465 of the textbook to help
you review what youve just studied. Once you understand
the material, move on to Assignment 4.
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Garden Ecology20
Self-Check 3
Match each term in the left column below with its definition in the right column.
______ 1. pH
______ 2. Pedology
______ 3. Humus
______ 4. Clay
______ 5. Soil structure
______ 6. Cation exchange
______ 7. Alluvial soil
______ 8. Air
______ 9. Acidic soil
______ 10. Alkaline soil
Check your answers with those on page 74.
a. A chemical reaction necessary for preventing essentialnutrients from being leached from the soil
b. The soil separate with the smallest particles
c. The relationship between hydrogen and hydroxyl ions thatindicates the acidity or alkalinity of a soil
d. The study of soils
e. A measure of soil pH thats less than 7
f. An organic colloidal component of soil resulting from theenzymatic breakdown of plant tissue
g. The arrangement of soil particles into aggregates
h. A type of transported soil resulting from the movement ofwater
i. A measure of soil pH thats greater than 7
j. An element that can make up 25% of the volume of soil
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Lesson 1 21
ASSIGNMENT 4: PLANT GROWTHREGULATORS
Read the following material. Then read Chapter 4, pages 6675,
in your textbook, Ornamental Horticulture.
Growth Regulators Defined
Just like you, plants produce chemical compounds that affect
their growth. In both plants and humans, these naturally
occurring chemical compounds are called hormones.
Hormones specifically related to plants are sometimes
referred to as phytohormones. Plant hormones control normal
plant functions such as root growth, stem elongation, and
other developmental processes. Plant hormones also deter-
mine the formation of flowers and leaves, the timing of leaf
senescence (the falling of leaves), the development and ripen-
ing of fruit, and even the ultimate death of a plant. Unlike
animals that have specialized glands that produce hormones
and a circulatory system that transports them, every plant
cell is capable of producing hormones that may exert their
effect in a completely different part of the plant. Just as in
the animal kingdom, hormones are vital to plant growth.
Without them, plants would most likely appear and function
in ways other than what were accustomed to.
Types of Growth Regulators
Plant growth regulators (PGRs) may occur naturally. Some
examples are auxins, gibberellins, and cytokinins (see
pages 6771). Other PGRs may be man-made. These com-
pounds mimic the functions and processes of naturally
occurring plant hormones. Theyre used in agriculture and
ornamental horticulture to achieve various growth character-
istics in plants and to enhance the desirable traits in food
crops and those same traits in ornamental plants.
Textbook Note
On page 71 of your textbook in the second full paragraph, the wordkinetic (line 3) should be kinetin.
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Garden Ecology22
The table below illustrates some of the more commonly used
PGRs, along with their functions and practical uses.
The use of plant growth regulators is less common among
landscapers than among those who grow agricultural and
ornamental crops. Nevertheless, if youre going to be working
in the landscaping field, you should have an awareness of the
effects that PGRs have on plant growth. You should also be
familiar with their potential uses and associated benefits. All
of these are valuable tools professional landscapers may use
in managing landscapes under their care. Here are two good
examples how this knowledge can be helpful:
1. Knowledge of a plants normal response to maintenance
practices such as trimming and pruning will allow you to
propose solutions to plant maintenance problems with
known results rather than by trial and error.
2. Plant growth retardants have been developed for use on
turfgrasses in an attempt to slow their rate of growth.
Applying these retardants properly to plants can give a
return in investment many times over in reduced labor
hours, fuel costs, and dumping/recycling fees.
Now, take a moment to complete Self-Check 4 and the
Achievement Review on page 76 of the textbook to help you
review what youve just studied. Once you understand the
material, move on to Assignment 5.
PGR Function Practical Uses
Auxins Promote or inhibit growth Stimulate root growth on plant cut-tings; encourage flower formation
Gibberellins Stimulate cell division and enlargementIncrease stalk length; enhance seedgermination and fruiting
Cytokinins Stimulate cell division andshoot formationProlong storage life of flowers andvegetables; stimulate bud initiation
Ethylene Influences leaf abscissionand ripening of fruitInduces uniform ripening in fruitsand vegetables
Abscisic acid Inhibits growthPrevents greenhouse plants frombecoming too tall or leggy; can promote early fruit and leaf drop
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Lesson 1 23
Self-Check 4
Match each term in the left column below with its definition in the right column.
______ 1. Auxins
______ 2. Geotropism
______ 3. Gibberellins
______ 4. Cytokinins
______ 5. Ethylene
______ 6. Parthenocarpic
______ 7. Rosetted
______ 8. Hormones
______ 9. Growth retardants
______ 10. Abscisic acid
Check your answers with those on page 74.
a. Growth habit of plants with good leaf formation butretarded intermodal growth
b. A term used to describe fruits without seeds
c. A naturally occurring growth inhibitor that counters theeffects of gibberellins
d. Plant hormones that both promote and inhibit plantgrowth
e. Naturally occurring compounds that influence plant growthand development
f. A term used to describe the response of auxin to gravityand the resulting growth reaction in plants
g. A group of plant hormones that promote cell enlargementand increases in plant height
h. Naturally occurring hormones that promote the division ofplant cells
i. A type of plant growth regulator that promotes the ripen-ing of fruit
j. Generic term used to describe growth regulators used inthe landscape trade to slow the growth of turfgrasses
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Garden Ecology24
ASSIGNMENT 5: PLANT REPRODUCTION
Read the following material. Then read Chapter 5, pages 7790,
in your textbook, Ornamental Horticulture.
The study of plant reproduction and plant breeding may
seem more appropriate to students pursuing a degree in
botany or greenhouse production. However, a basic under-
standing of the ways in which plants are produced for sale
to the landscape industry will enable you to make informed
choices when purchasing plants for your next landscape
project. After reading the material in your textbook, you may
decide to grow and propagate some plants yourself rather
than purchase them from a greenhouse or nursery. Many of
the plant reproduction techniques presented in the textbook
can be easily achieved with limited investment in tools and
materials. Many landscape professionals have incorporated
this aspect of ornamental horticulture into their business
plans, finding it to be both profitable and fun.
Sexual and Asexual Reproduction
Plants reproduce through either sexual or asexual
reproduction. Sexual reproduction relies on the formation
and pollination of flowers, followed by the development and
germination of seeds. When plants pollinate themselves, the
resulting plants are almost identical to the parents. When
plants pollinate with other plants, the resulting plants are
similar to but different than both parents because two sets
of chromosomes are combined to form one plant.
Asexual reproduction occurs through many different means
that bypass the lengthy flower-seed germination process.
Instead, this process of reproduction uses the vegetative
parts of a plant to produce an entirely new plant. Examples
of such vegetative parts are runners, stolons, sucker shoots,
bulbs, stems, and even leaves. These parts are described on
pages 8184. The plant that results from asexual reproduc-
tion is almost identical to its parent because theres no
combining of chromosomes from different plants.
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Lesson 1 25
Asexual reproduction allows plant breeders to make exact
duplicates of plants. While asexual reproduction provides
more reliable results, theres concern that without the cross-
pollination and mixing of chromosomes of sexual reproduction,
plants are unable to adapt or evolve in response to changes
in their environment.
The propagation of plants for use in the landscape trade is
generally carried out by those in the greenhouse and nursery
industry; however, the ease with which some plants can be
propagated makes it feasibleand profitablefor landscape
contractors as well. For example, because dividing a plant
crown is perhaps the easiest method of plant propagation,
landscape contractors would be wise to perform this job
themselves. Many shrubs and most herbaceous perennials,
such as the ever-present daylily or hosta, are easily divided
into two or more new plants by simply digging up the parent
plant and slicing it into smaller sections with a sharp shovel
or knife. These new divisions can then be planted back into
the garden or potted for use on another job.
At first read, some of the material in Chapter 5 of your text-
book may seem a bit overwhelming and difficult to follow. Try
not to get too hung up on the details. Instead, concentrate on
the overall concepts presented, rereading pages that cover the
more complex concepts of plant reproduction as needed.
Now, take a moment to complete Self-Check 5 and the
Achievement Review on pages 9193 of the textbook to help
you review what youve just studied. Once you understand
the material, move on to the examination for Lesson 1.
Caution
Many plants developed by plant breeders are patented. Because theycarry trademark protections, its illegal to propagate and sell theseplants without first paying a royalty fee to the breeder.
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Garden Ecology26
Self-Check 5
Match each term in the left column below with its definition in the right
column.
______ 1. Asexual reproduction
______ 2. Layering
______ 3. Propagation
______ 4. Clone
______ 5. Stratification
______ 6. Runner
______ 7. Bulb
______ 8. Grafting
______ 9. Cuttings
______ 10. Gregor Mendel
Check your answers with those on page 74.
a. The deliberate controlling and manipulation of plant reproduction
b. A propagation method in which two plants are joined andeventually become one plant
c. Pieces of plants removed for the purpose of propagation
d. A modified stem or root tissue that stores food duringdormant periods
e. A stem that grows along the ground surface forming newplants at the nodes
f. A process in which new plants are produced without theformation of seeds
g. An Augustinian monk who utilized the common gardenpea to study plant genetics
h. An exact duplicate of the parent plant achieved throughasexual means
i. A means of plant reproduction in which roots form on astem still attached to the parent plant
j. The exposure of seeds to low temperatures necessary forseed germination
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Garden EcologyIn Lesson 1, you learned the fundamentals of plant and soil
science. In this lesson, youll build upon what youve learned
about plants and soils by reviewing basic concepts and mate-
rials and by studying the complex interactions that occur
between plants, soils, and their surrounding environment.
This holistic approach to the study of plants, soils, and other
living organisms in the environment is the branch of science
known as ecology. While ecology can be studied at many lev-
els, the focus of this lesson is on the ecology of smaller-scale
landscapes and gardens. It also considers the influences and
roles played by human beings in the workings of these envi-
ronments. All of the assigned readings for this lesson are in
the textbook Ecology for Gardeners.
Assignment 6 provides a review and deeper explanation of
basic concepts and terms used in describing plants and the
way in which they function. Assignment 7 introduces you to
the many other living organisms besides plants and the roles
they play in a healthy ecosystem. Assignment 8 examines
the environmental factors, including the nonliving mineral
substances, that influence plants. Assignment 9 covers the
interactions of plants with natural forces and mineral
substances. Assignment 10 discusses the influences of com-
petition and mutualism in the garden environment. And
finally, Assignment 11 focuses on the role human beings
play in the stewardship and management of the garden
environment.
OBJECTIVES
When you complete this lesson, youll be able to
Use the proper scientific terms to describe the basic
parts and structure of a green plant
Describe the life cycle and various stages of growth and
development of a green plant
List and categorize the living organisms other than
plants that may inhabit the garden environment
27
Le
ss
on
2L
es
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n 2
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Garden Ecology28
Discuss the effects that other living organisms can have
on plant growth
Outline the environmental factors that influence plant
growth and soil formation
Summarize the primary energy inputs in the garden
environment
Describe the material cycles and their importance in the
garden environment
Characterize the interactions of plants with the natural
forces of heat, light, and gravity, along with other forces
that influence plant growth and development
Discuss the interactions of plants with mineral
substances
Describe the concept of plant communities and their
variation in space and time
Explain the concept of biodiversity
Summarize the interactions among garden organisms,
including competition, herbivory, predation, parasitism,
and mutualism
Provide an overview of the concepts of stewardship and
holistic management of the garden environment
ASSIGNMENT 6: THE NATURE OF PLANTS
Read the following material. Then read Chapter 1, pages 1145,
in your textbook, Ecology for Gardeners.
The love of plants often draws people to the landscape
professionand for good reason. Plants are fascinating in
their ability to transform the energy of the sun into food that
sustains all higher life-forms, including humans. Plants also
provide the raw materials people use to build shelters, pro-
duce medicines, and make the fibers used in the manufacture
of clothing and paper products of all sorts. The energy that
powers todays world economy ultimately finds its source in
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Lesson 2 29
the plants that covered the globe millions and millions of
years ago. For all that plants provide, landscape professionals
generally consider them as the foremost building blocks from
which attractive gardens and landscapes are made.
Just as a pre-med student must learn about the human
anatomy before working with patients, a landscape profes-
sional must also become familiar with the nature of plants
prior to successfully using them in a landscape. Make that
your goal as you study Chapter 1.
As you read the material in Chapter 1, you may begin to
wonder why you need to learn so much about plant parts
and about the way in which plants grow, develop, and repro-
duce. The answer is simple: Many of the books youll be
using as a landscape professional use this information to
describe and identify plants. If youre unfamiliar with these
terms, youll find it difficult to identify and choose plants for
a landscape project.
Much of the material youll study in this assignment was
introduced in Lesson 1. Let this assignment serve as a both a
review and further study of plants from another perspective
information that will reinforce your understanding and
appreciation of the subject matter.
Now, take a moment to complete Self-Check 6 to help you
review what youve just studied. Once you understand the
material, move on to Assignment 7.
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Garden Ecology30
Self-Check 6
Match each term in the left column below with its definition in the right column.
______ 1. Nodes
______ 2. Conifers
______ 3. Stomates
______ 4. Rhizome
______ 5. Root hairs
______ 6. Mycorrhizae
______ 7. Cotyledons
______ 8. Genus
______ 9. Meristems
______ 10. Species
Check your answers with those on page 75.
a. The first of the two-part Latin name given to each plant
b. Horizontal stems below the soil surface that produce roots andnew shoots
c. Points along the stem at which leaves and branches arise
d. Plants that generally have needle-shaped leaves or flat, narrowleaves that remain on the plants for several years
e. The second of the two-part Latin name given to each plant
f. Plant tissue where new cells form from the division of existingcells leading to plant growth
g. Pores on the surface of a leaf that allow water vapor to escapeduring the process of transpiration
h. The points along a plants root where the great majority of wateris absorbed
i. The parts of plants that provide a source of energy to newlyemerging seedlings prior to the formation of true leaves
j. Associations between plant roots and soil-borne fungi in whicheach usually benefits from the other
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Lesson 2 31
ASSIGNMENT 7: OTHER GARDEN INHABITANTS
Read the following material. Then read Chapter 2 (pages 4790)
in your textbook, Ecology for Gardeners.
Imagine that youre standing in the middle of a very large,
empty parking lot or in a barren desert on a hot summer day.
What do you see? What do you hear? Chances are you dont
see or hear much in the way of any life-form. Now put your-
self in the middle of a prairie on that same hot summer day,
and what do you see and hear? More than likely, youll hear
the buzzing sound of bees and wasps as they hover around
the multitude of prairie flowers and grasses. Youll see grass -
hoppers jumping from the tall grasses, hawks soaring on the
warm breezes above, and if youre lucky, a small herd of buf-
falo rumbling by. Now wander inside the cool shade of the
wooded ravine at the edge of the prairie and notice the sala-
manders and frogs in a shallow pool of water, a snake
winding its way through the bulrushes, and a spider making
a meal of the unlucky fly trapped in its web. Take a break on
the trunk of a fallen tree and notice the roaming army of ants
and the centipedes that scatter when you lift a piece of rotting
bark. Pick up a stick and brush aside the layer of decaying
leaves and twigs and take notice of the red worms and
ground beetles going about their business. Pick up a handful
of soil and take a closer look with your pocket lens and
observe the array of microfauna that go unnoticed to the
naked eye.
Now what does all that mean? Simply this: A landscape
devoid of plants is most likely going to be deficient in other
life-forms as well. On the other hand, a landscape with
plants will most likely be occupied by a diversity of animal
life. Some of these life-forms may be considered a nuisance
as in the case of a hungry deer that nibbles the succulent
growth of your hosta to the ground or a rabbit that lops the
flowers off your tulips just as theyre about to bloom.
However, others, such as the worms that aerate and enrich
the soil with their castings and the bees and wasps that polli-
nate flowers, are essential to the functioning of a garden
ecosystem. For a landscape professional, an understanding
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Garden Ecology32
and appreciation of the complex relationships between
plant and animal life in the garden environment are vital to
the care and stewardship of man-made landscapes.
In this assignment, youll be introduced to the nonplant
garden inhabitants that play vital roles in the functioning of
healthy garden ecosystems. Some, like hungry rabbits, are
readily recognizable and easily identified as either helpers or
nuisances to gardeners. However, others, like nematodes and
bacteria, may not be recognized so easily. An untrained eye
may jump to the conclusion that many of these less familiar
organisms are only something to be reckoned with and
immediately reach for the can of bug spray. In fact, these
organisms may be doing landscape plants a favor. Learning
to first identify and then separate the good guys from the bad
is the first step in maintaining healthy ecosystems while doing
as little harm as possible.
In reading through your textbook, try not to be intimidated
by the sheer number of hard-to-pronounce scientific names
of individual organisms. Instead focus on the big picture to
gain an appreciation of the diversity of life-forms in the gar-
den and how each contributes to a balanced and healthy
ecosystem.
Now, take a moment to complete Self-Check 7 to help you
review what youve just studied. Once you understand the
material, move on to Assignment 8.
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Lesson 2 33
Self-Check 7
Match each term in the left column below with its definition in the right column.
______ 1. Animals
______ 2. Herbivores
______ 3. Metamorphosis
______ 4. Caterpillars
______ 5. Omnivores
______ 6. True bugs
______ 7. Hymenoptera
______ 8. Detritivores
______ 9. Insects
______ 10. Earthworms
Check your answers with those on page 76.
a. Organisms that consume decomposed organic material
b. The larval stage of moths and butterflies
c. Organisms that are unable to photosynthesize and are composedof more than one cell
d. Organisms with three distinct body segments, including a head,a thorax, and a posterior abdomen
e. Organisms that eat both plants and animals
f. A term used to describe the multiphase life cycle of insects
g. Organisms that eat plants or plant parts
h. Organisms called the saints of the garden
i. Generally the most beneficial of all insect groups, which includesants, bees, and wasps
j. Relatively soft-bodied insects that have piercing-sucking mouthparts and undergo incomplete metamorphosis
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Garden Ecology34
ASSIGNMENT 8: THE GARDEN ENVIRONMENT
Read the following material. Then read Chapter 3 (pages 91
122) in your textbook, Ecology for Gardeners.
Up until this point, the focus of Lesson 2 has been on the
living constituents of plants and animals in the garden envi-
ronment. While plants and the animals that feed on these
plants are of great concern to landscape professionals, the
physical elements of sunlight, air, water, and soilalong with
their influences on the health of gardens and landscapes
deserve equal consideration in the study of designing and
caring for these unique environments.
Sunlight
As youve already learned, sunlight is the ultimate source of
all energybe it the gasoline that powers your rototiller, the
food you eat that keeps you going, or the direct rays of sun-
light that make garden plants grow. How gardeners and
landscape professionals make use of this amazing source of
energy rests on their knowledge of the physical properties of
sunlight, how it changes from one geographic location to
another, and how it changes throughout the year.
Air
The air that surrounds people and plants in the environment
is influenced by the energy of the sun. It, too, is an important
factor in the health of both plants and animals. While its
impossible to actually see the individual components that
comprise the atmosphere, a basic understanding of its chem-
ical makeup and the way in which it influences everything
from plant vigor to the health of soils will enable you to better
care for plants in the landscapes youre responsible for. To
better appreciate the influence air has on plants, consider the
wilting effects on a newly planted tree from a hot, dry, sum-
mer breeze or the sinking of cold air from high ground that
settles over a low spot in the landscape, resulting in an early
autumn frost and an abrupt end to the life of your coveted
tomato plants.
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Lesson 2 35
Natural Waters
A sufficient supply of water is often the difference between a
healthy plant and a dead one. The lack of waterif all other
needs of the plant are being metcan be the limiting factor
to a plants success. The most obvious effects that wateror
the lack of itcan have on an ecosystem can be seen in
places like the desert in the southwestern United States,
where this lack of water has a profound effect on the quan-
tity, size, and types of plants and animals that are able to
survive in the arid environment. As detrimental as the lack of
water may be to the survival of plants and animals, an over-
abundance of water can have equally unfavorable effects on
plant health. Saturated soils can become anaerobic and toxic
to plants. Water also affects the movement of soil nutrients
in a process known as leaching that over time can remove
essential soil nutrients. Such soil becomes unsuitable to
many plants unless chemical fertilizers are added to it.
An understanding of the physical properties of water and its
effects on plant and soil health is yet another vital compo-
nent in the successful handling of garden environments.
Soil
Often seen as nothing more than the medium by which
plants anchor themselves to the earth while absorbing the
nutrients and water essential to their survival, soil is a pre-
cious resource that through ignorance and neglect is being
depleted at alarming rates. In many instances, soils that have
taken hundreds and even thousands of years to form are
simply stripped away during the land development process,
rendering the site inhospitable to the sustainable growth of
plants. In such instances, common practice is to spread a
thin layer of topsoil over the disturbed ground after buildings
and roads have been constructed. However, the soil that
results is far from that which was there before the develop-
ment process began. If plants are to prosper and thrive in
such soil, some degree of remediation of the soils is required.
To carry out the vital process of rebuilding a healthy soil,
landscape professionals must possess knowledge of the com-
ponents and processes that form healthy soils. Armed with
this knowledge, along with an understanding of the many
The term anaerobicmeans without oxygen.
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Garden Ecology36
nutrient cycles that are critical to maintaining soil health,
landscape professionals avoid the costly mistake of taking
the soil for granted.
Now, take a moment to complete Self-Check 8 to help you
review what youve just studied. Once you understand the
material, move on to Assignment 9.
Self-Check 8
Match each term in the left column below with its definition in the right column.
______ 1. Loam
______ 2. Sunlight
______ 3. Humus
______ 4. Anaerobic
______ 5. Nitrogen
______ 6. Transpiration
______ 7. Limiting factor
______ 8. Material cycle
______ 9. Oxygen
______ 10. Clay
Check your answers with those on page 76.
a. The gas that comprises 7880 percent of the air in the loweratmosphere
b. A process that results in the greatest loss of soil water throughthe leaves and stems of plants
c. A series of transformations in which a substance begins andends in the same form
d. An energy source that drives evaporation, wind currents, and the process of photosynthesis
e. A soil-borne substance composed of very large organic mole-cules derived from the remains of dead plants, animals, andmicrobes
f. A soil with a more-or-less balanced blend of sand, silt, and clayparticles
g. The gas that comprises 1820 percent of the air in the loweratmosphere
h. A type of soil thats prone to shrinking, swelling, and compaction
i. A critical resource or factor whose deficiency or excess limits thegrowth of a plant
j. A condition in which free oxygen is scarce or absent such as instagnant water or compacted soils
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Lesson 2 37
ASSIGNMENT 9: PLANTS IN THE ENVIRONMENT
Read the following material. Then read Chapter 4 (pages 123
167) in your textbook, Ecology for Gardeners.
To survive in the environment, plants must be fighters, or
they at least must be able to adapt to the whims of nature.
Unlike animals, plants lack the ability to move about in
search of food, water, warmth, or even a mate. To make up
for this lack of mobility, plants have many clever ways in
which to adapt to surrounding environmental conditions.
The ability of plants to adapt in response to natural forces
such as heat and light, or to the physical and mineral prop-
erties of different soil types has resulted in an astounding
diversity of plant life here on Earth, each precisely suited to
the unique environment in which it grows.
Interactions of Plants
with Natural Forces
Heat
When selecting plants for a garden, landscape professionals
give their greatest consideration to two criteria: plant hardi-
ness and sunlight requirements. As youve already learned,
plant hardiness refers to the ability of a particular plant to
survive a minimum cold temperature. This factor is a very
important consideration in the selection of appropriate plants
for a garden. In addition, duration and variation in air tem-
perature play equally significant roles in the life cycle and
survival of many plant species in temperate climates.
Light
The second consideration is sunlightin particular, how
much sunlight a particular plant needs to flower, set fruit,
and thrive in a landscape. To expect a plant that has existed
for years in the moist, shaded rainforest environment of the
Pacific Northwest to suddenly adapt to the blazing sun of an
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Garden Ecology38
arid and treeless backyard in Texas is a lot to ask. And con-
versely, the sun-loving prairie blazing star that blooms so
profusely in the open prairie wont flower the way you had
hoped when planted in your customers shaded backyard.
Interactions of Plants
with Mineral Substances
After temperature and sunlight requirements, soils and their
mineral makeup, along with moisture levels, are probably the
next most significant limiting factors in the survival of plants.
Minerals
The creation of soil, which occurs over a long span of time, is
directly influenced by the underlying parent material of rock
and other mineral formations. The plants that grow in associ-
ation with these varied soil types are specially adapted to
them. Therefore, theyll perform poorly when suddenly placed
in soils of a different composition.
Consider this example: People have tried to plant an acid-
loving rhododendron in a limestone-based, alkaline soil.
These attempts generally result in failure. While soils can be
modified and made more hospitable to certain plants through
the addition of various minerals and nutrients, this task can
be quite expensive on a large scale and can easily be avoided
by selecting plants suited to the soils youre working with.
Water
In nature, water is often the most critical limiting factor in
plant survival. With the aid of aqueducts and irrigation
ditches in pre-modern times and the garden hose and exten-
sive underground irrigation systems of today, people have
found a way around the limiting factor that a lack of water
can present. The problem, however, is that this artificial
means of sustaining plants has tremendous environmental
costs. Therefore, planting indigenous species in favor of
exotic species that may not be adapted to local conditions
should be strongly considered.
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Lesson 2 39
Although the lack of water is a definite limiting factor, too
much of it can be equally limiting to plants ability to thrive
in the landscape, as many a drowned Japanese yew can
attest.
While some of the effects on plants from too much or too lit-
tle water can be quite obvious, others such as the leaching of
nutrients from the soil go unnoticed but can have significant
consequences on soil fertility and plant health. Chapter 4 in
your textbook goes into more detail on the effects of water
and other soil nutrients essential to plant health and their
influences on evolution of plant communities.
Now, take a moment to complete Self-Check 9 to help you
review what youve just studied. Once you understand the
material, move on to Assignment 10.
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Garden Ecology40
Self-Check 9
Match each term in the left column below with its definition in the right column.
______ 1. Vernalization
______ 2. Sexual
reproduction
______ 3. Respiration
______ 4. Etiolation
______ 5. Water
______ 6. Hardening off
______ 7. Pruning
______ 8. Nitrogen
______ 9. Potassium
______ 10. Sodium
Check your answers with those on page 76.
a. The growth condition involving excessive stem elongation andpale color, usually due to inadequate light levels
b. The practice that compensates for root loss in perennials duringtransplanting
c. A chemically inert substance that must be converted before itcan be used by plants
d. The plant process thats especially sensitive to excessively hightemperatures
e. A nutrient important to the proper growth of root systems andtheir ability to take up nutrients from the soil
f. In low-light situations, the process that exceeds the rate of pho-tosynthesis and leads to exhaustion of a plants energy reserve
g. The process in which flowering is induced by exposure to a mini-mum period of cold
h. A substance thats highly toxic to plants and devastating to soilstructure; the sixth most abundant element in Earths crust
i. The most critical nutrient for plants and the main source ofhydrogen required for photosynthesis
j. The process of preparing indoor-grown plants for harsher, out-side growing conditions
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Lesson 2 41
ASSIGNMENT 10: INTERACTIONSAMONG GARDEN ORGANISMS
Read the following material. Then read Chapter 5 (pages 169
238) in your textbook, Ecology for Gardeners.
The study of plants, animals, and the nonliving components
of the garden environment is a logical first step in under-
standing the ecology of gardens. The next important step is to
consider the ways in which these living organisms interact
with each other and their surrounding environment. A simple
way to consider these interactions is to determine whether
the effects they have on one another are positive or negative.
For example, a caterpillar that feeds on the leaves of a young
tree is fat and happy, while the tree has been stripped of all
of its leaves1 for the caterpillar, 0 for the tree. Then, in flies
a bird that eats the plump caterpillar1 for the bird, 0 for
the caterpillar. Its not always clear who are the winners and
losers as new players continually join the game. What should
be clear, however, is that something seen as negative at one
point may later be perceived as positive. As a landscape pro-
fessional, you should approach your study of gardens and
landscapes from a holistic and ecological point of view. Such
a view is much more challenging and interesting than the
shortsighted approach that sidesteps the wisdom of nature
in favor of the quick fix at the end of a spray nozzle.
Competition
Competition among organisms can be classified as either
intraspecific, in which individuals of the same species com-
pete against each other, or interspecific, in which organisms
of differing species compete for the limited resources in the
environment. Plants have developed an amazing array of
mechanisms that allow them to compete with other plants in
their quest for the limited resources in the environment. One
example of such a mechanism is very familiar to gardeners
who have tried to plant a garden in the vicinity of a black
walnut tree. This particular species of tree has the ability to
produce the chemical compound juglone, which is toxic to the
other plants around it. Other tactics such as early or rapid
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Garden Ecology42
growth, the ability to survive in a wide range of growing
conditions, and the ability to produce and disperse prolific
amounts of long-lived seeds over great distances are exam-
ples of a plants competitive abilities.
Plants arent always in direct competition with each other,
however. At times, plants cooperate by occupying different
niches in the environment. For example, in forest environ-
ments, the shade-loving groundcover plants thrive in the
shadow cast by overhead canopy trees.
Herbivory
Perhaps more menacing to plants than the competition
among plant species is the threat of herbivory, in which all
or part of a plant is consumed by other organismsincluding
people. Herbivory comes in many forms:
The chewing of leaves by hungry caterpillars
The draining of a plants vital fluids by thirsty aphids
The consumption of fruits and seeds by birds and
mammals
In response, plants have developed both physical and chemi-
cal methods to deter predators. For example, some plants
have stiff bristles on the surface of their leaves and stems,
and others produce bitter-tasting tannins. While a certain
level of herbivory is basic to the normal functioning of the
food web, populations of certain organisms may occasionally
become a detriment to the garden environment and peoples
desire for some level of control over nature.
As a landscape professional, you should have the ability to
maintain a certain level of control in the garden. This ability
begins with a basic understanding of the various methods by
which plants are preyed upon by other organisms and the
methods of identifying the culprits. Specific actions you can
take to control the spread of unwanted plant pests are cov-
ered in forthcoming assignments.
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Lesson 2 43
Other Interactions
Chapter 5 also covers the topics of predation, parasitism, and
the win-win interactions among garden organisms known as
mutualism. A mutualism familiar to many gardeners is that
which occurs between the Rhizobium bacteria and plants in
the legume family, such as peas and beans. In this instance,
the bacteria that live on the roots of a pea plant make it possi-
ble for the plant to absorb atmospheric nitrogen. In return, the
bacteria are allowed to absorb nutrients from the pea planta
win-win situation for both the bacteria and the pea plant.
An appreciation of these and the many other complex inter-
actions that naturally occur among garden organisms will
enable you to work in harmony with, rather than against, the
natural rhythms of the garden ecosystem.
Now, take a moment to complete Self-Check 10 to help you
review what youve just studied. Once you understand the
material, move on to Assignment 11.
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Garden Ecology44
Self-Check 10
Match each term in the left column below with its definition in the right column.
______ 1. Alleopathy
______ 2. Seed bank
______ 3. Herbivory
______ 4. Gall
______ 5. Physical defense
______ 6. Tannin
______ 7. Mimicry
______ 8. Parasitism
______ 9. Mutualism
______ 10. Mycorrhizae
Check your answers with those on page 76.
a. A situation in which all or part of a plants tissues or fluids areconsumed by another organism
b. A tumor-like growth on leaves or stems that provides shelterand food to invading organisms
c. A form of competition among plants in which one plant releasesa chemical thats harmful to other plants
d. Spines, bristles, and thorns, which serve to protect plants fromherbivores
e. A defense tactic whereby a plant produces plant parts thatresemble other plants in an attempt to confuse or deceive predators
f. A long-term association between two or more species in whichall participants benefit
g. Fungi that live in close association with plant roots, helping themextract nutrients from the soil
h. A buildup of seeds in the soil in excess of what was produced inthe preceding year
i. A chemical defense common in tea leaves and acorns
j. An interaction in which one individual removes nutrients, fluids,or tissues from another over an extended period of time
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Lesson 2 45
ASSIGNMENT 11: GARDENINGAS APPLIED ECOLOGY
Read the following material. Then read Chapter 6 (pages 239
274) in your textbook, Ecology for Gardeners.
Putting the Environment First
As a landscape professional, you should always work in such
a way that does as little harm as possible to the natural
landscape. In fact, you should attempt to restore any damage
that may have inadvertently been caused by others.
All kinds of people work in the landscape. Some are simply
backyard gardeners with small vegetable plots; others are
landscape designers who are creating plans for entire yards.
No matter the person, however, the goal should be the same:
to follow the example set by nature and garden or landscape
just as nature does. To illustrate this point, consider the
statement made by architect and author William McDonough
in his book Cradle to Cradle: In nature, the word waste does
not exist. If thats true, then why do so many people rake
the leaves from their yards each fall and send them to the
landfill or compost center instead of composting them in their
own yards where they can nourish the soil the way it happens
in any healthy forest ecosystem? Granted, it isnt always pos-
sible or practical to fully mimic nature in some places and
under certain circumstances, but adherence to this philoso-
phy as the guiding principle in every decision related to
landscapes can result in gardens and landscapes more in
tune with nature and a landscape industry thats a better
steward of the environment.
Most people dont intentionally do things they know are
going to be harmful to the environment. However, many,
through ignorance of the complex interactions that occur in
healthy ecosystems, do so in their attempt to improve the
environment around them. They may plant a tree ill-suited to
existing site conditions that leads to the spraying of harmful
chemicals, or they may attempt to maintain a lush bluegrass
lawn in an arid climate by applying copious amounts of water
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Garden Ecology46
and fertilizer. Such decisions result in losing battles that
consume precious resources and work against the laws of
nature.
In your work with landscapes, dont always look for the quick
and easy fix of synthetic herbicides, pesticides, and fertilizers.
In the long run, such solutions often create more problems
than they solve and at unnecessary environmental costs.
Instead, heres a good approach to take with the landscape
environment:
Make concern for the environment a top priority.
Be willing to be patient with low-tech, proven methods.
Stewardship
As you study Chapter 6, youll notice that a key term in that
chapter is stewardship. This term is used in relationship to
soil (pages 240241), water (pages 241242), and the atmos-
phere (page 243).
Soil is a precious, life-supporting resource. To be a good
steward of soil, you can
Help to keep it aerated by maintaining a high level of
organic matter in the soil
Control erosion
Take measures to avoid compacted soil
To be a good steward of water, you can
Follow the principles of xeriscaping by using drought-
tolerant plant species in arid climates
Apply a protective covering of mulch to reduce the
amount of water lost through evaporation
To be a good steward of the atmosphere, you should give
careful consideration to the placement of trees in the land-
scape. Proper tree placement can result in lower ambient air
temperatures as well as lower amounts of energy required to
cool a house on a hot summer day.
Xeriscaping is theprocess of gardening insuch a way to eliminatethe need for supple-mental water fromirrigation.
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Lesson 2 47
These simple, low-cost strategies that eliminate the need for
more costly solutions down the line are all part of being a
good steward of the environment and should be standard
procedure rather than the exception to the rule. Other sug-
gestions are presented on pages 240243.
Managing Garden Organisms
Gardens have enemies. Its just a fact of life. These enemies
may be other plants, animals, or insects. Possibly the best
advice for dealing with these enemies is that mentioned on
page 244 of your textbook: From an ecological perspective,
however, it may not be desirable, even if feasible, to utterly
eliminate garden pests. Instead, we should try to manage
both pests and their often more numerous desirable garden
neighbors for the greater welfare of the garden and the envi-
ronment as a whole. Pages 243264 present a variety of
environmentally safe ways to deal with these enemies.
Finally, the last few pages of Chapter 6 cover the ways in
which you can effectively manage plant nutrients, soil
amendments, and energy in a gardenthree important ele-
ments you must consider as a landscape professional.
Now, take a moment to complete Self-Check 11 to help you
review what youve just studied. Once you understand the
material, move on to your exam for Lesson 2.
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Garden Ecology48
Self-Check 11
Match each term in the left column below with its definition in the right column.
______ 1. Terracing
______ 2. Hardpan
______ 3. Landscape fabrics
______ 4. Trap crop
______ 5. Fallowing
______ 6. Crop rotation
______ 7. Companion plant
______ 8. Systemic
______ 9. Green manure
______ 10. Hilltops
Check your answers with those on page 77.
a. One ecologically sound way to prevent the growth of weeds
b. A plant species that herbivorous insects prefer over otherplants in a garden
c. One method to reduce soil erosion on steep slopes
d. A technique of starving herbivorous insects by leaving a plotof ground bare for a period of time
e. A plant that either repels harmful organisms or attracts beneficial ones
f. Another term for a cover crop in which plants are grown andtilled into the soil for soil improvement
g. An area that tends to offer longer frost-free growing seasonsthan does land in a valley setting
h. A situation that can be created when soils are repeatedlytilled to the same depth or are walked on when wet
i. A technique to lower herbivorous insect populations bygrowing unrelated plants in succession on the same plot ofground
j. A type of fungicide thats absorbed by a plant and cant bewashed off
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Fundamentals of CommonSense Pest ManagementHere are some of the topics youll be studying in Lesson 3:
Common causes of injuries sustained by plants in the
landscape as well as disease and pest problems that can
weaken and, in extreme cases, kill plants
Natures way of controlling pests
How an integrated approach to pest management
utilizing beneficial insects and other less toxic control
methods is better for you and the environment
The strategies and tactics used in an integrated pest
control system that can be implemented in an effort to
lessen the damage done by unwanted garden pests and
the misuse of toxic chemicals
Assignment 12 presents a broad overview of plant pests
and control methods used in maintaining healthy plants.
Assignment 13 is an introduction to natural pest controls
and the fine balance that exists in nature, in which living
organisms (including those considered pests) control their
own populations. In Assignment 14 youll revisit the subject
of integrated pest management (IPM), but in much greater
detail, and youll learn about the various treatment strategies
applied in IPM. In Assignment 15 youll be introduced to the
multitude of beneficial insects and other organisms that are
an integral part of a successful IPM program. Assignment 16
will teach you how to choose the right chemical or microbial
tools along with other useful inorganics, organics, and botan-
icals when beneficial organisms alone won't do the trick.
Finally, in Assignment 17 youll discover the new frontiers of
microbials, pheromones, and insect growth regulators being
utilized in IPM programs today.
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Garden Ecology50
OBJECTIVES
When you complete this lesson, youll be able to
Discuss the major causes of injury to plants
List common symptoms of injured plants
Describe conventional methods used in controlling plant
pests
Describe an integrated approach to pest management
(IPM)
Describe natures role in pest management
Identify the treatment strategies and tactics utilized in
an IPM system
List the beneficial insects and other organisms utilized in
IPM
Discuss the conventional use of chemicals in controlling
pests and the ramifications to both environmental and
human health
Describe less-toxic alternatives to pest control
Discuss the use of microbials, pheromones, and insect
growth regulators in an IPM system
ASSIGNMENT 12: PLANTINJURIES AND THEIR CONTROL
Read the following material. Then read Chapter 6 (pages 94
135) in your textbook, Ornamental Horticulture.
Assignment