Lepidium latifolium

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Lepidium latifolium

Family: Brassicaceae

Common names: perennial peppergrass or peppercress, slender perennial peppercress, broadleaved or broadleaf pepperweed, tall whitetop, giant white weed, iron weed

Description

Perennial pepperweed grows up to 6 feet tall and has basal leaves that are lance shaped, have long petioles, are up to 12 inches long, and are covered with a waxy layer. Stem leaves are smaller and have shorter petioles, but don't clasp the stem. Leaves have a prominent, whitish midvein. Flowers are white, less than 1/8 inch wide, and are borne in dense, rounded clusters at the branch tips from early summer until fall. Fruits are roundish, slightly hairy, measure 1/16 inch in diameter, and contain 2 tiny seeds.

Location

Throughout California, except deserts and northern North Coast and adjacent mountains (Del Norte, Humboldt, n Mendocino cos.); to Canada, Montana, Indiana, Texas. Also, regions of the Northeastern U.S. To ~ 2000 m (6500 ft). Wetlands, riparian areas, meadows, salt marshes, flood plains, beaches, roadsides, irrigation ditches, agronomic crops, especially alfalfa, orchards, vineyards, irrigated pastures, ornamental plantings. Typically grows on moist or seasonally wet sites. Tolerates saline and alkaline conditions.

Culture

Heavy infestations are difficult to control. Cleaning agricultural or earth-moving machinery after use in infested areas and curtailing movement or use of soil, hay, and crop or pasture seed contaminated with perennial pepperweed root fragments and/or seed and can help prevent new infestations. Single techniques, such as repeated mowing, hand-digging, cultivation, grazing, and burning, typically do not adequately control perennial pepperweed. In addition, cultivation may increase infestations by dispersing root fragments. Field observations suggest that plants may not tolerate an extended period of flooding during the growing season.