Extension Viewpoints: Noxious weed of the month: perennial pepperweed


By Ethan Proud
PREVIEW Columnist

Perennial pepperweed is also known as tall or giant whitetop, and if you read the article on whitetop, you know what to expect. The inflorescences or flowers look much the same, though perennial pepperweed is much taller, growing from 3 to 6 feet tall and has spoon-shaped leaves. 

It is in the mustard family (brassicacea) and can be identified by scent similar to broccoli if the leaves are crushed. Like whitetop, this plant may be toxic and grazing is not a recommended control.

It spreads both by seeds and rhizomes and, as such, digging the plant will result in many more shoots emerging from the infestation. While pepperweed plants can produce thousands of seeds, their main mode or reproduction is through a creeping root system. The roots of this plant can be found deeper than 2 feet in the soil. Root fragments as small as half an inch can resprout a new plant. 

Seeds produced by perennial pepperweed are often not viable, though laboratory tests indicate that seeds may remain dormant for up to two years before germinating. Perennial pepperweed is a versatile plant that can thrive in riparian areas as well as extremely dry soils and can be found along Mill Creek and in Arboles. Treatment with selective herbicides is recommended and prolonged spring flooding can kill new growth. 

Archuleta County Weed and Pest is your local resource for managing noxious weed populations and controlling other pests.

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