Wildflowers Found in Oregon

Perennial Pepperweed (Tall Whitetop, Ironweed, Giant Whiteweed)

Lepidium latifolium - Description: A herbaceous perennial in the Mustard family (Brassicaceae). Plants are multiple stemmed and grow in stiffly erect masses 3 to 8 feet tall. Leaves are lanceolate, bright green to gray green, and entire or toothed. Basal leaves are stalked, up to 1 foot long and 3 inches wide and have serrate margins. Leaf size decreases up the stem. Flowering occurs from early summer to fall. Abundant small white 4-petaled flowers are borne in dense clusters near the stem tips. The fruits are small, flattened pods about 1/10th inch long, each containing 2 seeds (1 per chamber). Fruits remain on the plant, dropping irregularly throughout the winter. The base of the stem is semi-woody. The creeping roots enlarge at the soil line, forming a woody crown. The plant mainly propagates clonally from its brittle rhizome-like roots that grow to a length of up to 6 feet.

Habitat: Perennial pepperweed occurs in riparian (stream) areas, coastal wetlands, marshes, roadsides, railways, ditches, hay meadows, pastures, cropland, and waste places. Nonnative.

Distribution: It occurs in a few states along the eastern seaboard, in several Midwestern states, and in all far western states. Infestations have been reported in coastal, intermountain and mountainous areas in New England, all the states west of the Rocky Mountains. It also occurs in Canada and Mexico.