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WHAT IS A NOXIOUS WEED?

'Noxious Weed' is the traditional, legal term given to nonnative plants that have been proven to have a negative impact on the environment, and are destructive, competitive, and/or difficult to control. 

Noxious weeds arrive in our region in a variety of different ways, such as ornamental garden plants, wildflower seed mixes, agricultural crops, contaminated hay or seed, or from vehicle tires along transportation corridors.

 

Once established, noxious weeds  crowd out desirable vegetation, reduce agricultural productivity, compromise public health and safety, lower property values, increase flood hazards, and destroy native plant and animal habitat.

 

"THE TERRIBLE TEN"

The Top Ten Noxious Weeds That Threaten Pierce County

 


Common Fennel
  • Licorice scented perennial 4-10 ft. tall
  • Leaves are dark green and feathery
  • Umbrella shaped clusters of small yellow flowers
  • Tap roots can reach depths of 10 feet
  • Outcompetes native plants and reduces native wildlife habitat
  • Once established it is difficult to control, due to strong competitive abilities and persistent seed bank


Dalmation Toadflax
  • Perennial herb 2.5 to 5 feet tall
  • Waxy, heart shaped, light green leaves
  • Bright yellow flowers tinged with orange center, looks like a snapdragon
  • Persistent, aggressive invader, pushes out native grasses and other perennials
  • Rapidly colonizes open sites
  • Contains poisonous alkaloid, toxic to livestock


Wild Chervil
 
  • Biennial plant grows from 1 to 4 ft. tall
  • Hollow ridged stems with fern-like leaves
  • Small, white umbrella shaped flower clusters
  • Serious threat to native plants and agriculture
  • Highly adaptable, will grow in almost any type of soil
  • Has an aggressive growth habit, quickly creates a monoculture
  • Most of Pierce County is highly susceptible to Wild Chervil infestation

Tansy Ragwort

  • Invasive, persistent, toxic biennial
  • 1st year: rosette stage; dark green basal leaves, ruffled in appearance
  • 2nd year: one or more flowering stalks bolt up to 6 ft. tall
  • Numerous yellow, daisy-like, flowers with 13 petals
  • Contains toxins that cause chronic irreversible liver damage; a threat to livestock and agriculture.

Poison Hemlock

  • Toxic biennial plant up to 8 ft. tall
  • 1st year: basal rosette with fern like leaves.
  • 2nd year: produces hollow, hairless stems with purplish splotches and dark green, glossy, fern-like leaves
  • Umbrella shaped clusters of small, white flowers
  • All plant parts are extremely poisonous to humans and livestock
  • Wear gloves and protective clothing when handling this plant, can cause contact dermatitis
  • Do not burn or compost this plant

Knapweeds

  • There are 3 species of knapweed that threaten Pierce County: spotted, diffuse, and meadow knapweed
  • 1st year: rosette form
  • 2nd year: flowering stalk elongates
  • Spine tipped, or fringed bracts (leaf-like structure at the base of the bloom) arranged in an imbricate pattern, like shingles on a roof
  • Flowers are lavender to pink and sometimes white
  • Very aggressive species, one of the most dominant weeds of the west, can infest large areas very quickly
  • Contains phyto-toxins which inhibit the growth of surrounding native plants, allowing knapweed to form monocultures
  • Has very long tap roots


Gorse
  • A dense, spiny, evergreen shrub, 3-10 ft. tall, closely resembles scotch broom
  • Aggressive, invasive plant crowds out other vegetation, forms impenetrable thickets
  • Has sharp thorn-like leaves up to 3 in. long
  • Clusters of bright yellow, pea-like flowers form into pods containing 1 to 4 seeds
  • Plants form a center of dry, dead vegetation, that coupled with its high oil content creates a serious fire hazard



Perennial Pepperweed
  • Bushy, perennial plant usually1 to 3 ft. tall, may reach up to 6 ft.
  • Alternate, waxy leaves with white mid-vein
  • Rounded clusters of small white flower at branch tips
  • Displaces desirable native plants
  • Poses serious threat to natural areas, wildlife habitat, pastures, rangeland, and coastal areas
  • Destabilizes river and stream banks, increases soil erosion



Giant Hogweed
  • Huge perennial plant from15-20 ft. tall.
  • Hollow stem 2 to 4 in. in diameter, with dark reddish, purple splotches and white bristles
  • Large compound leaves, up to 5 ft. wide with jagged edges
  • White umbrella shaped, flower-heads up to up to 2.5 ft. wide
  • Clear watery sap causes ultraviolet skin sensitivity, resulting in severe burns, blisters and scars
  • Sap can squirt up to 5 ft. when stem is cut or broken.
  • Do not handle without gloves, goggles and protective clothing

 



top ten worst weeds in Pierce County, WA
 Shiny Geranium
  • Low growing annual, 10 to 12 inches high
  • Stems are tinged bright red
  • Leaves are rounded, divided into 5 to 7 lobed sections, shiny and bright green, turning red in late summer & fall 
  • Pink flowers grow in pairs and have 5 petals
  • Invades woodlands, forest openings, open grasslands and native habitat