Healthy Soil for Healthy Plants by Kelby Fite, Ph.D.

Structural Pruning: The Key to Strong Treesby Bruce Fraedrich, Ph.D.

Nurserymen typically prune trees annually or more often to produce a desirable form. Young, developing trees grow rapidly. Pruning is essential to provide a straight stem, proper branch distribution and a strong structure for future growth. Structural pruning should not stop in the nursery. A young tree that is transplanted into the landscape continues to grow rapidly and requires the same training that occurred in the nursery. The focus in the landscape is to maintain a single central stem unless multiple stems are desired. Maintaining branch size also is critical to avoid weak attachments and potential storm damage. As the tree grows in size, the canopy may require thinning to provide branch definition and low branches may be removed to provide needed clearances.

Ideally, structural pruning should begin as soon as trees become established following transplanting and continue until maturity. Depending on species, trees may require attention every year or two when young and frequency can be extended to every three-to-five years as a large crown develops. Structural pruning should not be restricted only to large maturing shade trees, short maturing species such as dogwood, crab apple, cherry and Japanese maple also benefit

from structural pruning as do conifers and other evergreens.

Soil. What is it? Sure it is sand, silt, clay and some organic matter, but it is so much more complex than that. Soil is alive and

active. It is startling just how complex it is. How many of us actually take time to think about soil? Probably not enough. We take it for granted. However, when our beloved landscape plants begin to suffer, it is frequently a result of the neglect we have shown to the soils that support them. Landscape soils are often damaged from grading, construction activities, and mismanagement.

In order to restore soils, attention must be paid to chemical, physical and biological health. A soil chemistry test is an easy first step to take in the rehabilitation process. This will give you an indication of nutrient levels, pH, and organic matter content. Physical status can be evaluated by collecting a bulk density sample to determine the level of compaction and soil texture. The soil biology is a more complex variable to assess since it is constantly changing. The biology of the soil is effected by chemical and physical properties as well as the plant material. Adding organic matter as a food source for microbial communities to flourish, encourages biological activity and can be done in conjunction with physical and chemical treatments, such as Root Invigoration®.

The bottom line is soils must be a focal point when managing landscapes. Many of the plant health problems we face are a result of unhealthy soils. By sampling soils, we can understand their deficiencies and begin a program for restoring an environment where a diverse biological array can flourish, recycle nutrients and build long-lasting soil stability. These programs can sometimes be disruptive in the short-term, but must be undertaken to reduce other inputs into the landscape in the long-term.

Bartlett’s Root Invigoration®

de-compacts the soil and adds

nutrients

Biochar can be added to soils

as a permanent home for microbial

communities

A soil sample is one of the

initial steps in evaluating the

soil health.

TREE TIPST R E E & S H R U B C A R E F R O M B A R T L E T T T R E E E X P E R T S

AUTUMN 2013

Disease Alert -To date, 2013 has been a prolific year for Fire-blight disease in California trees. Caused by a bacterium (Erwinia amylovora), this disease is capable of infecting and causing unsightly damage on any plants in the family Rosaceae, and is most commonly seen in California causing blight on Pear, Apple, Hawthorn, Loquat, and Quince. The name ‘fire-blight’ refers to the symptoms of blackened or dark brown branches and foliage, which often form a hook at the tip where the original infection occurred. In pears in California, the infection may begin lower on the branch, which can cause the uninfected growing tips to turn purple as the lower infection girdles the branch.

The infection is primarily spread into the flowers through bee activity and then the bacteria moves from the flower into the twigs and towards the main trunk. Once infected, cankers form on trunks and large branches, and these perennial cankers are the source of future spread within a tree, often leading to tree death. The bacterium is active during the moist and humid weather of spring and spreads between and within susceptible trees during that time. In winter and summer, the bacterium is normally dormant but symptoms in infected tissue may continue to worsen during this time. In the San Francisco Bay area, the active period of the bacterium is extended due to the fog and humidity associated with the ‘Marine Layer’.

Management of fire-blight requires sanitation and prevention. Sanitation pruning, or removal of all infected tissue, should be performed in summer or winter when the bacterium is dormant and spread of disease has ceased. On highly susceptible trees and rapidly advancing infections, pruning

should be performed immediately upon symptom recognition even if the bacterium is still active. This is the only time of year when sterilization of pruning tools may be advised, but the need for sterilization is not supported by experimental evidence. In late winter and during the spring infection period, prevention of new infections can be achieved through protective applications of a copper-based product. Copper as an active ingredient in disease management is also an organic material. It is rare to get complete control over any plant disease, but limiting infections through sanitation and prevention will limit dieback and avoid major infections that often lead to plant disfigurement or mortality.

Widespread Fire-Blight Infections in California by Drew Zwart, Ph.D.

In fire-blight disease the bacteria moves from the flower into the twigs and towards the main trunk.Above:Typical fire-blight symptomsLeft: Discoloration of infected pear in California

Asian Persimmon Gaining Popularity by Patrick Brewer

The Asian Persimmon is easy to grow with beautiful, ornamental fruit and foliage; additionally persimmon is relatively free of pests. The Asian Persimmon, Diospyros kaki is native to China, and is adaptable to many soils and climates, from acid to alkaline and hardiness zone 7 through zones 10.

Asian persimmon is self-fruitful and can be planted alone without a pollenizer, and flowers are borne on the new growth so no special pruning skills are required to maximize the crop. The only trick to persimmon is the fruit, which can be astringent or non-astringent, depending on the variety. Non-astringent varieties like “Fuyu” can be eaten firm and crisp, while the astringent varieties like “Hachiya” and “Eureka” must be soft-ripe before eating. Either variety has beautiful, persistent fruit and striking green foliage.

Persimmon fruit is high in antioxidants, vitamin A and vitamin C, and fiber. While naturally a medium-sized tree, Persimmons make excellent fruit trees for small spaces as they tolerate pruning and shade well and even make nice espaliers.

Count the total number of leaves in this drawing.

How Many Leaves?

California Oakworm by Donald Booth, Ph.D.

Check the answers at www.bartlett.com/puzzles or by scanning this QR code with your smartphone.

What’s a QR Code? A type of barcode which you scan with a smart phone to immediately access additional information or a web site. In selected printed material, like Tree Tips, we may occasionally include a QR code that will link you to additional information online.

When the population is high, oakworms can defoliate virtually every oak in a region.

Close up of an oakworm.

California oakworm is the only North American species in a group of neotropical moths called the American False Tiger Moths. This may not matter to the owner of oakworm defoliated trees, but this is a unique insect with some strange habits:

1. Most areas have two generations per year. An unusual aspect of this life-cycle is the “overwintering generation”, where female moths lay eggs in the fall and young caterpillars spend the winter on the underside of evergreen oak leaves.

2. In outbreak years, overwintering oakworms can completely defoliate trees by May or June. The subsequent summer generation may cause defoliation in July through September.

During years when populations are high, oakworms will defoliate virtually every oak in a region.

3. Trees under stress from drought or other factors may decline if defoliated. Healthy trees can tolerate some oakworm damage, but it is important to prevent oaks from being defoliated twice in a short time.

4. The adult moths fly during the daytime, increasing the nuisance of living near an outbreak. When oaks have been defoliated, the caterpillars become a major issue, often traveling everywhere in landscapes.

One of the interesting garden spots at the arboretum, located near the main building.

Book ReviewsTrees and Shrubs for the Southwestby Mary Irish

Gardeners in the Southwest need to choose plants that are adapted to the rigors of the southwestern climate. This book has profiles of more than 200 of the most attractive, easy-to-grow, and climate appropriate trees and shrubs. There is expert information about how to use trees and shrubs in the garden, how to plant and care for them, and how to combat common pests and diseases. Also includes instructions on common tasks such as planting, staking, and pruning. Homeowners who want to create an attractive, sustainable landscape will find no better

resource.

Trees, Shrubs and Vines for Attracting Birdsby Richard M. DeGraaf

Revised and updated, this new edition of a much sought-after classic remains the best source for information about the trees, shrubs, and vines

that provide bird habitats and feeding sources in the United States, Canada and beyond. More than 160 species of trees, shrubs, and vines that provide food, cover, and nesting for common North American birds are highlighted, with instructions on designing a landscape habitat that attracts desired bird species.

Tree and Shrub Gardening for Northern Californiaby Bob Tanem and Don Williamson

This book has detailed listings for 78 different species of trees and shrubs, along with information on 399 recommended varieties and cultivars best suited for Northern California gardens. Listings include size, shape, growing zone and other specifics. There is information on what tree or shrub to select for a specific location; how to plant, prune and propagate; and solving pest and disease problems.

Tip Blights on Cedars by Drew Zwart, Ph.D.

or black. The disease is most common in the lower canopy or in shaded regions of the plants because these areas are typically cooler and remain moist longer than upper canopy or foliage exposed to full sun. Trees that are stressed by environmental or soil issues are also more susceptible to the disease. Only new growth is susceptible to infection, and the infections spreads from developing needles into twigs, eventually killing all of the current year’s growth.

Management of this disease involves sanitation and preventative treatments. Removal of dead twigs and fallen needles will reduce the amount of inoculum for new infections. Preventative fungicides applied in the spring as the new needles emerge and expand will

LAB NOTESTip blight, or dieback of developing twigs, is an increasingly common disease affecting Blue Atlas cedar and Deodar cedar across Canada. The disease is caused by a fungus (Diplodia pinea or Sphaeropsis sapinea), and is favored by cool and wet spring weather, making it particularly common. This pathogen is most commonly found causing dieback of 2- and 3-needle pine species, but many other conifers are susceptible. Cedrus species are often infected by spores produced on nearby pines. Symptoms of infection include dieback of developing twigs, which turn brown

protect susceptible new growth. There are also several other fungal pathogens that cause branch cankers and tip death of these cedars, so accurate diagnosis should be sought prior to making management decisions.

Diplodia pinea fungus in a blue atlas cedar

TREE TIPS

published by THE F. A. BARTLETT TREE EXPERT COMPANY(877) BARTLETT (877-227-8538) in U.S. and Canada • www.bartlett.com

For Tree Tips information contact smurdock@bartlett.com © 2013 The F. A. Bartlett Tree Expert Company

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