A native of southern Europe and western Asia, perennial pepperweed establishes rapidly and colonizes pastures, riparian habitats, and wet areas, as well as along roadsides, in rangelands and field crop situations. It degrades nesting habitat for wildlife and displaces desirable species in natural areas and hay meadows. It lowers digestibility and protein content of hay and inhibits grazing.
Perennial pepperweed is most abundant along the Duwamish River on industrial lands. It is also found in patches on the Puget Sound shoreline and on the shores of Vashon Island.
Legal status in King County, Washington
This Class B weed has a limited distribution, and control is required in King County. This species is also on the Washington quarantine list (known as the prohibited plants list) (external link) and it is prohibited to transport, buy, sell, offer for sale, or to distribute plants or plant parts, seeds in packets, blends or "wildflower mixes" of this species, into or within the state of Washington.
Biology and morphology
Pepperweed generally grows 1 to 3 feet tall, but can reach up to 6 feet. It has many stems that emerge from a somewhat woody root crown with alternate, waxy leaves that have smooth or toothed margins and a prominent, whitish midvein. Basal leaves are lance-shaped and up to 12 inches long; they are attached by a stalk that can be almost as long as the leaf blade. Stem leaves are smaller, with shorter stalks. Perennial pepperweed's delicate, milky white flowers, which are sometimes collected for dry flower arrangement, grow in dense, rounded clusters at branch tips. Plants flower from June through September, producing small (1/16 inch) round or egg-shaped fruits. This plant spreads through profuse seed production and extensive, creeping roots. It has adapted to a wide range of habitats.
Additional information on perennial pepperweed
What to do if you find this plant in King County, Washington
Please notify us if you see perennial pepperweed growing in King County. Our program staff can provide the property owner or appropriate public agency with site-specific advice on how best to remove it. Also, because perennial pepperweed is not established in King County, we have an opportunity to stop it from spreading if we act quickly. We map all known locations of regulated noxious weeds such as perennial pepperweed in order to help us and others locate new infestations in time to control them.
Perennial pepperweed photos - click thumbnail for larger image