Aquatic Noxious Weeds in King County

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Aquatic Noxious Weeds in King County

• King County Noxious Weed Control Program
• www.kingcounty.gov/weeds

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Agenda

• Overview Definitions, Impacts, and Laws
• Priority Aquatic Invasive and Noxious Weeds in
  King County

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What is an Invasive Weed?

• Introduced / non-native
• Ability to out-compete native plants
• Lack of predators or natural controls
• Ability to modify local ecology
• Aggressive ability to reproduce
• Not all introduced plants are invasive but most
  invasive plants were brought here intentionally

Fragrant water lily on Cottage Lake
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Impacts of Aquatic Weeds

• Clog waterways
• Impede recreation
• Foul motors
• Replace native plants
• No wildlife value
• Alter water chemistry

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How is a Noxious Weed Defined?

• Non-native plant that damages agriculture,
  wildlife, human health, land values or natural
  resources
• Defined and regulated by state law (RCW 17.10)
• control required only where weed is not
  widespread
• goal of law is to prevent spread of new invaders
  to un-infested areas

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Two Lists Growing vs. Selling Noxious Weeds

• Noxious Weed List (WAC 16-750)
• Highest priority is where weeds are beginning to
  invade
• List set primarily by state weed board law
  enforced by county noxious weed boards
• Requires property owners to prevent plants from
  seeding
• Prohibited Plants List (WAC 16-752)
• Goal is to prevent spread of new introductions
• List is determined by WSDA, enforced by state
  Nursery Inspection Program
• Prohibits sale and purchase of plants and seeds

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State Weed Categories

• Class A (39 on list 14 found in KC)
• non-native, invasive, very limited distribution
• eradication required throughout state
• control provides statewide benefits (sometimes
  even greater)
• Class B (51 designated in KC 28 present)
• non-native, invasive, split distribution
• where limited, control required by state law
• where widespread, county board decides on control
• control provides regional or countywide benefits
• Class C (only 3 selected for control in KC, 31 on
  state list most too widespread to require
  control)
• widespread distribution, county decides on
  control
• control provides local or site-specific benefits
  more if efforts are coordinated with neighbors

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Four Most Common Regulated Noxious Weeds in King
County
Tansy Ragwort
Purple Loosestrife
Garden Loosestrife
Giant Hogweed
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Other King County Weed List Categories

• Non-Regulated Noxious Weeds
• State-listed Class B and C weeds that are
  widespread in the county control recommended but
  not required
• For example milfoil, knotweed
• Weeds of Concern
• Not technically noxious weeds according to state
  law considered invasive vegetation in King
  County control desirable especially in natural
  or agricultural areas

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Meet the LOOSESTRIFES and other aquatic Noxious
Weeds
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THE LOOSESTRIFES
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Garden Loosestrife Lysimachia vulgaris
Class B Noxious Weed
2-10 foot tall perennial of wetlands and
shorelines
Flowers showy yellow primrose-like flowers
clustered at top of stem (terminal
pannicle) Flowers in July and August Leaves
opposite or whorled (in threes or fours), leaves
usually have small orange or black glands visible
with magnification
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Produces extensive red rhizomes that will reach
out up to 10 feet into the adjacent open water
Stems have soft hairs and are round, occasionally
flattened (fasciated)
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Garden Loosestrife Lysimachia vulgaris
Class B Noxious Weed
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Shade
66
Full sun
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Snohomish County
King County
Garden loosestrife distribution in King County
Duvall
Kirkland
Sammamish River
Matthews Beach Magnuson Park Union Bay Montlake
Park Lk Wash. Blvd Seward Park
Redmond
405
Bellevue
Rutherford Slough
90
5
Fall City
Raging River
Issaquah
Lake Alice
Renton
Lake Burien
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Garden loosestrife Impacts
Ecological displaces native plants and animals
interferes with wetland food web and habitat
clogs small streams Economic clogs irrigation
systems water control structures dominates wet
pastures
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Garden loosestrife ImpactsOutcompetes other
aggressive plants
Himalayan blackberry
Purple loosestrife
Common cattail
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Purple loosestrife Lythrum salicariaClass B
Noxious Weed

• 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
• flowers July and August

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Look-alikesPurple loosestrife vs. spirea and
fireweed
Purple loosestrife Douglas spirea Fireweed (ha
rdhack)
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Snohomish County
Purple loosestrife distribution in King County
King County
Duvall
Redmond
Bellevue
Seattle
Snoqualmie River
Issaquah
Renton
Vashon Island
Federal Way
Green River
Auburn
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other common aquatic noxious weeds (and native
look-alikes)
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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

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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

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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

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Myriophyllum spicatum Eurasian watermilfoil
Class B non-designate

• Key characteristics
• 14 or more leaflet pairs
• leaves whorled
• usually red stem, branched
• leaves generally collapse against stem when
  pulled from water
• flower spike held above water

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Eurasian watermilfoil Myriophyllum spicatum vs.
the native northern watermilfoil Myriophyllum
sibiricum
The native has fewer than 14 leaflet pairs
Eurasian water Milfoil has 14 or more leaflet
pairs
Collapses out of water
Holds shape out of water
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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

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Egeria densa Brazilian elodea Class B
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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

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Brazilian elodea vs. our native American
waterweed Elodea canadensis
Brazilian elodea usually has 4 leaflets
Native usually has 3 leaflets
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Dozens of other submerged natives in Lake
Washington
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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

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A Few Less Common Regulated Aquatic and
Shoreline Weeds
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Glyceria maxima Reed sweetgrass Class A

• Key characteristics
• Emergent perennial grass, sometimes variegated
• Up to 2.5 m (gt8 ft.) tall in up to 2 m (6 ft.) of
  water
• Leaves stiff and smooth
• Ligule papery, rounded and pointy
• Flowers in summer, inflorescense open and branched

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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

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Myriophyllum aquaticum Parrotfeather Class B

• Key characteristics
• emergent up to 1 ft. above water
• leaves in whorls around stem
• leaves feathery like milfoil
• dense mat of brownish rhizomes

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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

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Phragmites australis Common Reed Class C
designate

• 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
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Impatiens glandulifera Policemans Helmet
Class B
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Spotted Jewelweed - Impatiens capensis (control
not required but strongly encouraged)
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Invasive Knotweed Class B Non-Designate(control
not required but strongly encouraged)
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Hollow, upright, bamboo like stems often reddish
or red-speckled
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Grows so thickly that nothing can compete with it
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Except maybe garden loosestrife!
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King County Noxious Weed Control Program Website
www.kingcounty.gov/weeds
Weed Photo Page Search by Common Name or Latin
Name
Or click thumbnail picture of plant for weed
information and photos
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Sasha Shaw and Katie Messick King County Noxious
Weed Program201 South Jackson St, Suite
600Seattle, WA 98104206-296-0290 (program
line) www.kingcounty.gov/weeds