King County

Weed Watchers

2008Program

Introduction to plant categoriesNative: native plants are those that occur naturally in an

area. They include rare or uncommon plants (such as water buttercup or buckbean), common, often aggressive plants (such as american waterweed or hardhack), and even a few that have invasive strains of the same species introduced from elsewhere (such as common reed).

Introduction to plant categoriesIntroduced: introduced plants are those non-native plants

that are growing in natural areas but are not causing significant damage (at least not yet!) These include escaped garden plants and weeds (such as creeping jenny), and other naturalized plants of unknown origin. Some, such as common forget-me-not, can be very difficult to tell from their native cousins (small-flowered forget-me-not). A few (such as narrow-leaved cattail) are being watched as potential noxious weeds.

Creeping jenny

Small- flowered & common forget-me-not Narrow-leaved

cattail

Introduction to plant categoriesNoxious weeds: “noxious weed” is a legal designation – any

introduced plant that is causing problems can be added to the official noxious weed list by the Washington State Noxious Weed Control Board (the process differs in other states). In Washington there are three main categories of noxious weeds.

Introduction to plant categories

Noxious weed classificationClass A weeds (such as hydrilla) have limited distribution in Washington. Preventing new infestations and eradicating existing ones are the highest priorities. Eradication of these species is required by law.

Class B weeds (such as purple loosestrife and Brazilian elodea) are abundant in some areas of the state and less common in others. Regionally less common species are designated for control by the County Weed Board. Control and containment of these species is required by law.

Class C weeds (such as fragrant waterlily) are common throughout most of Washington. Control is encouraged but not required by law.

Introduction to plant categories: the plot thickens

Class C designate: weeds (such as common reed) that the King County Weed Board has designated as priority weeds in the County. Control and containment of Class C designate

weeds is required by law.

Class B non-designate: Class B weeds (such as Eurasian watermilfoil) that are so prevalent in the County that the County Weed Board does not require their control. Control is encouraged but not required by law.

“Designate” vs. “Non-designate”

Introduction to plant categories: summary

NATIVE generally beneficial

INTRODUCED usually not harmful

NOXIOUS always potentially destructive

Class A

Class B designate and non-designate

Class C designate and non-designate

Weed Watchers is concerned primarily with Class A weeds and Class B and C designate

weeds

Plant identification

There are often multiple Common Names for one plant, and the multiple plants can have the same common name. Common names can be easier to remember, but they can confuse the identification of a particular plant.

Latin Names can change over time as the scientific community updates taxonomy based on new research. Both Genus and species names can change over time. Latin names can be difficult to remember if you are unfamiliar with them, however, they are a more reliable identifier than common names.

EXAMPLE:

spatterdock = yellow pond lily = yellow water lily = Nuphar lutea = Nuphar polysepala

A Note on Plant Names

Useful plant concepts: annual

perennialrhizome

Note: these and other botanical terms are described in appendix A of your field guide (An Aquatic Plant Identification Manual)

Important plant terms: leaf arrangements

opposite alternatewhorled

compound

leafleaflet

basal

leaf axil

Submerged

Leaves divided

Leaves feather-like Leaves not feather-like

Leaves paired and opposite Fanwort

Leaves in a whorl all the way around the stem Coontail or aquatic plant-like algae (Chara or Nitella sp.)

Leaves simple

Leaves in whorls around stem

Leaf margins visibly toothed, leaves in whorls of five Hydrilla

Leaf margins smooth

Leaves alternate on stem

Leaves thin, leaf margins wavy Curly-leaf pondweed

Leaves elliptical to thread-like, sometimes have floating leaves Native pondweeds

More than 14 leaflets per leaf, leaves collapse against stem when removed from water Eurasian water milfoil

Fewer than 14 leaflets per leaf, plant holds its shape when removed from water Native milfoils

Leaves more evenly distributed on stem

Leaves clasp stem, tend to bunch at stem ends Water-nymph

Leaves have bladders Bladderwort

No bladders

Leaves mostly in whorls of three American waterweed

Leaves in whorls of four (up to six) Brazilian elodea

Leaves scaly, rather rigid and overlapping along entire length of stem Water moss

Leaves not rigid, have mid-vein(s)

Gray boxes = invasive plant

White boxes = native plant

10 submerged species you should be able to identify

Latin name Common nameCabomba caroliniana fanwort – Class B

Ceratophyllum demersum coontail -native

Egeria densa Brazilian elodea – Class B

Elodea canadensis American waterweed - native

Hydrilla verticilata hydrilla – Class A

Myriophyllum spp. native watermilfoils

Myriophyllum heterophyllum Variable watermilfoil – Class A

Myriophyllum spicatum Eurasian watermilfoil – Class B non-designate

Potamogeton crispus curly leaf pondweed – Class C non-designate

Utricularia vulgaris common bladderwort - native

Cabomba caroliniana Fanwort – Class B

Key characteristics:• submerged leaves

opposite, fan-shaped

• small white flowers borne above the water

• plant can look cylindrical underwater

Currently not in King County

Ceratophyllum demersum Coontail – Native

Key characteristics:• leaves narrow, forked and whorled on the stem

• inconspicuous flowers

• plant is stiff and holds its shape out of water

Egeria densa Brazilian elodea – Class B

Key characteristics:• smooth leaf edges

• leaves in whorls of 4 (up to 6)

• relatively showy flower

• grows in up to 20 feet of water

Elodea canadensis American waterweed – Native

Key characteristics:• leaves linear, whorled in 3s (sometimes 2-4) on the stem

• leaves sparse toward bottom of plant, more bunched together toward top

• branching stem fragments

Brazilian elodea vs. our native American waterweed Elodea

canadensis

Native has3 leaflets

Brazilian elodea has 4 leaflets

Hydrilla verticillata Hydrilla - Class A

Myriophyllum species:The trouble with milfoils

# of leaflets variable and overlapping

Stem color and thickness variable

Flowering stalks helpful, but not always diagnostic

DNA analysis sometimes necessary

Got a new milfoil population? Send us a sample!

Myriophyllum heterophyllum Variable watermilfoil – new Class A

Key characteristics:• Submerged leaves: • 5-18 leaflet pairs

• limp leaves in whorls of 4-6

• densely packed, bottlebrush appearance

• Emergent leaves (bracts):• Toothed, entire, stiff, less toothy higher on stem

• ½-1 inch long

• Stem green to red, robust • Plants can grow in de-watered areas

variable watermilfoil Myriophyllum heterophyllum vs. western watermilfoil Myriophyllum

hippuroidesBottom line: if it has emergent leaves, send it

in!!!

variable western

• Both have leaves on emergent flower stalks

• Both are rare or unknown in King County

• May require DNA analysis to tell apart

Key characteristics:• 14 or more leaflet pairs• leaves whorled • usually red stem, branched• leaves collapse against stem when pulled from water

• flower spike held above water

Myriophyllum spicatum Eurasian watermilfoil – Class B non-designate

Eurasian watermilfoil – Myriophyllum spicatum vs. the native northern watermilfoil Myriophyllum

sibiricum

Eurasian water Milfoil has 14 or more leaflet pairs

The native has fewer than 14 leaflet pairs

Collapses out of water

Holds shape out of water

Potamogeton crispus Curly leaf Pondweed - Class C non-designate

Key characteristics:• leaves distinctly wavy and stiff

• leaves olive green

• grows from early spring into summer

• major problem in the midwest but so far not a problem in Washington

Utricularia vulgaris Common bladderwort – Native

Key characteristics:• branched leaves• conspicuous bulbous bladders

green when young and turn black further down the stem

• carnivorous plant• small yellow snapdragon-like

flower is held above the water• plant often

prostrate on lake bottom

Native submerged species you should be familiar with

Latin name Common nameIsoetes spp. quillwort

Najas flexilis slender water-nymph

Potamogeton species native pondweeds

Ranunculus aquatilis water buttercup

Chara spp. muskgrass

Nitella spp. nitella

Isoetes spp. Quillworts – Native

Key characteristics:• clumping plant with bulbous base

• leaves stiff, grass-like, hollow, generally less than 24cm long and taper to a point

• several species in Washington, all native, submerged species all evergreen

• no flowers; reproduces by spores

Najas flexilis Slender water-nymph – Native

Key characteristics:• branched stem, up to 2m long,

fragments easily• slender pointed leaves <3cm long

cluster near top of stem• leaf base clasps stem and is much

broader than leaf blade• flowers inconspicuous

Potamogeton spp. Submerged pondweeds – Native

Key characteristics:• many species• leaves alternate, grass-like to

oval, always have at least one mid-vein

• stems branched, flexible, up to 3m long

• small flowers/seedheads on spikes held above water

Ranunculus aquatilis water buttercup – Native

Key characteristics:• uncommon in western King

County

• submerged leaves alternate, short stalked, highly branched

• occasionally present floating leaves are scalloped, <2cm wide

• white buttercup flowers with yellow centers are either held above water or submerged

• can be mistaken for fanwort (which has opposite leaves)

Chara spp. and Nitella spp. Plant-like algae – Native

Key characteristics:• algae has no leaves

• leaf-like branchlets form whorls around stem; undivided in Chara spp., evenly forked in Nitella spp.

• Chara spp. have strong, garlic-like odor, especially when crushed

• can be up to 2m long or as short as a few centimeters

Floating and mat-forming species you should be familiar

withLatin name Common nameBrasenia schreberi Watershield - native

Nuphar lutea Spatterdock or yellow pond-lily - native

Nymphaea odorata fragrant waterlily – Class C non-designate

Nymphoides peltata Yellow floating heart – Class B

Potamogeton species native pondweeds

Myriophyllum aquaticum

Parrotfeather – Class B

Ludwigia peploides Floating primrose-willow – Class A

Ludwigia palustris Water purslane - native

Brasenia schreberiWatershield – Native

Key characteristics:• Entire, oval leaves about

4” long with stem attached to center

• Inconspicuous purplish flowers

• stem, buds and lower leaf surface covered with slippery gelatinous substance

Nuphar luteaspatterdock, yellow pond lily – Native

Key characteristics:• very large heart-shaped leaves• ball-shaped yellow flowers• stems rigid enough to hold leaves out

of water when water level drops

Nymphaea odorata Fragrant waterlily – Class C non-designate

Key characteristics:• floating perennial

• flowers white to pink on separate flexible stalks

• thick fleshy rhizomes

• round leaves

Nymphoides peltata Yellow Floating Heart – Class B

Key characteristics:• floating perennial• small yellow flowers with

distinctive fringes• 2 to 5 flowers per stalk • heart-shaped or round

leaves, wavy margins, often purplish underneath

Currently not in King County

Myriophyllum aquaticum Parrotfeather – Class BKey characteristics:• emergent up to 1 ft. above

water

• leaves in whorls around stem

• leaves feathery like milfoil

• dense mat of brownish rhizomes

Ludwigia peploides Floating Primrose-willow – Class A

Key characteristics:• prostrate or floating

stems

• alternate, variable leaves

• bright yellow 5-petalled flowers in leaf axils

• Grows in up to 10 feet of water, can be up to 2 ½ feet tall

Ludwigia palustris water purselane – Native

Key characteristics:• leaves opposite, smooth

edged, elliptical, on long stalks

• flowers inconspicuous, greenish, in leaf axils

• stem prostrate to erect or floating, fleshy

• can form floating mats

Emergent species you should be familiar with

Latin name Common nameEpilobium hirsutum hairy willowherb – Class C designate

Iris pseudacorus yellow-flag iris – Class C non-designate

Lysimachia vulgaris garden loosestrife – Class B

Lythrum salicaria purple loosestrife – Class B

Phragmites australis Common reed – Class C designate

Polygonum amphibium water smartweed – native

Polygonum hydropiperoides waterpepper – native

Potentilla palustris marsh cinquefoil – native

Spirea douglasii hardhack, Douglas spirea – native

Typha angustifolia narrow-leaved cattail – non-native

Typha latifolia common cattail – native

Veronica americana American speedwell – native

Epilobium hirsutum Hairy willowherb – Class C designate

Key characteristics:• semi-aquatic perennial

rhizometous herb to 6 feet tall

• leaves mostly opposite, toothed, lanceolate

• co-exists with purple loosestrife

• wind-dispersed seeds like fireweed

• flowers July and August

• manual control difficult due to rhizomes

Native Epilobium species • There are many native epilobiums• Fireweed (E. angustifolium) is tall and

has showy flowers like hairy willowherb, but is an upland plant and usually will not be found in wet soils

• Several low growing, variable Epilobium species may be found in wet areas, but they will have small, relatively inconspicuous flowers

Epilobium angustifoliumEpilobium ciliatum

Iris pseudacorus – Yellow Flag Iris Class C non-designate

Key characteristics:• perennial monocot to 1.5 meters tall

• thick rhizomes form solid mats

• showy yellow flowers• green seed pods with flat seeds like corn kernels that float

Lysimachia vulgaris Garden Loosestrife – Class B

Key characteristics:• perennial emergent with rhizomes up to 15 feet long

• showy yellow flowers clustered at top of plant

• leaves opposite or whorled (3-6)

• leaves sometimes have small orange or black glands

• stems round, occasionally fasciated (flattened)

• flowers July and August

Lythrum salicaria Purple loosestrife – Class B

Key characteristics:• perennial rhizomatous

emergent with showy magenta flower spikes

• Branched stems are square, can root at nodes

• leaves opposite, lanceolate • up to 2.5 million tiny

seeds/plant

Phragmites australis Common Reed – Class B

Key characteristics:• 12+ foot tall rhizometous grass• hollow woody stems • wide stiff leaves• large feathery flower head purplish when young, brown in seed

Duwamish: First Avenue South

Native Polygonum species

Key characteristics:• Alternate lance-shaped

leaves• spikes of pink or white

flowers • P. amphibium is fairly

common• P. hydropiperoides is

fairly uncommon

Polygonum amphibium: Water smartweed

Polygonum hydropiperoides:

waterpepper

Potentilla palustrisMarsh cinquefoil – Native

Key characteristics:• compound leaf with 3-7 sharply toothed

leaflets at the end of a long stalk• stems prostrate or floating, extend up to ½

meter above the water surface • flowers have 5 reddish petals turning purple

in late summer

Spirea douglasii hardhack, Douglas spirea – Native

Key characteristics:• woody deciduous shrub• leaves alternate, oblong, toothed at the tip• tiny pink flowers in large spikes at stem ends,

appear fuzzy • spent flower spikes are dark brown and

persist through the winter• can be mistaken for purple loosestrife

image © Robert Flogaus-Faust

Cattails Typha latifolia: common cattail – nativeTypha angustifolia: narrow-leaf cattail –

introduced Key characteristics:• leaves narrow and up to 1.5 meters long• stems round, pithy and up to 3 meters

tall • T.latifolia: male and female flowers

adjacent on stem• T. angustifolia:male and female flowers

separated by 1-4cm on stem

Veronica americanaAmerican speedwell – Native

Key characteristics:• leaves oval to lance-shaped, toothed,

opposite• flowers blue-violet, small (<10mm), in

groups on long stalks from leaf axils• stems creeping to erect, <80cm• grows in up to 4 inches of water