A nightmare before weeding...
Giant hogweed is a 15-foot-tall plant
with sap that burns
your skin; tansy ragwort poisons and kills livestock; gorse is a dense shrub
that helped burn down a town. The economic impacts of noxious weeds in
agricultural areas or croplands are well known, but urban areas and natural
resources are not immune to impacts from destructive, invasive plants.
What is a Noxious
Generally speaking, noxious weeds are non-native plants
that are tough survivors, they are aggressive, very difficult to control and
native plants can’t compete with them.
These invasive characteristics and their impacts are what get them on
“the weed list.” But, those
characteristics alone do not make a weed noxious. Noxious weeds are the plants adopted by the state noxious
weed control board, and they are regulated for control by county noxious weed
Where Did These Plants Come From?
of our noxious weeds are native to Europe and Asia
or the Mediterranean region. Some
were accidentally introduced when agriculture was brought to the New
World. Others were introduced in
early trade. European ships carried soil or water as ballast to provide
stability at sea. The ballast was
dumped on shore, and if often contained seeds or plant parts. Purple loosestrife was
to the Northeastern Seaboard in ballast.
Some garden plants lead a double life—they
have a dark
side with bad habits. Quite a few noxious weeds originate as garden plants, or
as aquatic ornamentals for ponds or aquariums. English ivy, garlic mustard and
yellow flag iris all escaped the confines of their garden homes to outcompete
native and beneficial plants in their own homes.
Needless to say, not all exotic garden
capable of being a noxious weed.
Many introduced plants behave themselves, and you only find them where
you plant them, year after year.
The “escapees” quietly and steadily build a seed bank or an impressive
root system. The seeds sail along
on the wind or plant fragments float downstream or they hitchhike on tires,
shoes or animals to a more disturbed site – like a roadside or stream or
wetland. From there, the
opportunities for impact of invasive plants are boundless. They overwhelm
natural areas, agriculture areas or grazing lands, they choke waterways used
for recreation, irrigation or salmon habitat.
What is the “Weed List?”
New plants infest about 4,600 acres per year in
Washington State. In order to deal
with destructive plants that arrive and thrive in our state, the Washington
State Noxious Weed List is updated annually. A primary function of this list and of regulatory weed
programs is to prevent the new establishment of invasive weeds, and to control
the plants that are established.
Once plants make it on “the weed list” landowner control or eradication
is required by law.
The Washington State Department
of Agriculture (WSDA)
regulates the quarantine list. It is illegal to buy, sell or offer for sale,
some known invasive plants. It is
illegal to distribute seed packets, flower seed blends or “wildflower mixes” of
Want to learn more?
For more information on noxious weeds, or noxious weed
laws, please contact the King County Noxious Weed Control Program (206)
296-0290 or visit http://dnr.metrokc.gov/weeds.
State Noxious Weed Control Board website: