Perennial pepperweed, or tall whitetop, is a member of the Mustard family. It was introduced from either southern Europe or western Asia. It is a deep-rooted perennial plant with an extensive, vigorous, creeping root system which reproduces by seed and root stalks. Perennial pepperweed is similar to whitetop.
Perennial pepperweed stands 3 to 5 feet high with a heavy, sometimes woody, crown. The lower leaves are oblong with toothed margins. The upper leaves do not clasp the stem as in whitetop. Flowers are white.
Perennial pepperweed can be found in pastures, riparian areas, roadsides, and waste places. It has a limited range in north central and south central Colorado from 5,500 to 8,000 feet. In areas where the weed grows in Colorado, such as in the San Luis Valley and along the South Platte drainage, the plant has taken over thousands of acres.