This page was updated on Monday March 17 2008
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Perennial Pepperweed
(Lepidium latifolium):
Foreign invader in California's wildlands
What is it?Perennial pepperweed is a herbaceous plant in the mustard family. Plants survive several years and produce very thick, monospecific stands, especially in moist areas such as wetlands and along rivers and creeks. Perennial pepperweed has other common names, including tall whitetop, perennial peppercress, ironweed, perennial peppergrass, and broad-leaved pepperweed. Botanically it has also been called Cardaria latifolia. |
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Plants start from seed or pieces of perennial root. In early spring, the plant emerges from these perennial roots as a rosette, a growth form in which the leaves spread radially from the stem and stay very close to the ground. Later in the spring, the rosette will produce a flowering shoot. These shoots grow 2 to 5 feet tall and begin to flower in late spring in the Central Valley and later in more mountainous regions. Leaves are elongated, about 1 to 2 inches wide and 4 to 12 inches long. These leaves lack hairs, have either smooth or slightly toothed margins and are grey-green in color. |
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Each shoot will produce thousands of small, white, cross-shaped flowers. Each flower results in one small seed capsule containing two seeds. A thick infestation of perennial pepperweed has been estimated to produce over 6 billion seed per acre. These seed are apparently short-lived in the field and do not appear to germinate well, but may still contribute to the spread of perennial pepperweed to new locations. |
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Perennial pepperweed creates an extensive perennial root system that reaches depths greater than 10 feet in the soil to reach the water table. This underground system becomes established early in the life of the plant and can persist for several years. The roots spread laterally from the parent plant up to 10 feet per year.
Semi-woody crown and perennial roots of perennial pepperweed |
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