Perennial pepperweed is invasive primarily in riparian areas and wetlands and may invade adjacent areas once established. 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.

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.

Perennial Pepperweed- Integrated Pest Management for Home Gardeners and Landscape Professionals

An aggressive plant, perennial pepperweed tends to establish and rapidly colonize pastures, riparian habitats, and waste places in wetter areas. The plant can also be a problem in roadside, rangeland, and field crop situations. It often reaches fields via irrigation ditches from riparian areas. Dense infestations of the plant can form near monocultures. The extremely competitive plant may also completely displace more desirable species, which poses a particular threat to natural areas.