Perennial Pepperweed (Lepidium latifolium), also known as tall whitetop, belongs to the mustard family. It is considered a noxious weed in several states, and has been an issue in the Basin and Range Region for a while now. Originally from Eurasia, it is now found in much of the United States. It is thought that it was brought in as a contaminant in sugar beet seed in the early 1900s.
Perennial Pepperweed tends to grow in riparian areas, along stream banks, irrigation ditches, meadows and other moist places, but can also be found in drier upland areas, such as roadsides, pastures, and agricultural fields.
Growing upwards of 6 feet tall, perennial pepperweed typically grows to between 2-4 feet in height. In early spring, it starts as a basal rosette, then stems grow out of the rosette. The leaves are bright green and the lower leaves are petioled (having a little stem between the main stem and base of leaf) and upper leaves are sessile (base of leaf is attached directly to the main stem), but this varies quite a bit. Also, the rosette leaves are about 4-11 inches long and 1-3 inches wide, but the leaves become smaller towards the top of the stem. The flowers form dense clusters arranged in panicles (branched inflorescence) at each stem. The flowers are small and white with 4 petals. Seed pods are round and flat, usually covered with hairs.
Perennial Pepperweed has extensive root systems that make it hard to control, as new shoots can sprout up from the roots. Some roots creep horizontally and are fairly shallow beneath the soil, others penetrate deep into the soil. The roots that creep horizontally tend to be responsible for localized spread.
Perennial pepperweed reproduces from both seed and its creeping roots. Mature plants can produce thousands of seeds each year. Also, roots and seeds float, which means plant material can be transported long distances by water and can establish new populations miles downstream from the original site.
Perennial pepperweed grows very aggressively, forming dense colonies that exclude native species. It reduces the quality of wildlife habitat, especially in riparian areas where it interferes with the regeneration of willows and cottonwoods, important habitat for birds and nesting waterfowl. The shallow, creeping roots also lead to erosion along stream banks and other areas.
Early detection and rapid removal is the best way to control perennial pepperweed, an established population is much harder and costly to manage. Mowing, digging, tillage, burning and grazing established stands are NOT effective, however, it has been found that small, un-established populations can be controlled with hand pulling, removing as much of the root as possible--but you must take caution not to spread the plant material as it can create new populations and exacerbate the problem. Pesticides have been the most effective of controlling these plants.
Sources and where you can learn more:
Great Basin Invasive Weeds, Perennial Pepperweed:
http://www.usu.edu/weeds/plant_species/weedspecies/pepperweed.html accessed 2/25/2015
USDA Forest Service, Lepidium latifolium:
http://www.fs.fed.us/database/feis/plants/forb/leplat/all.html accessed 2/25/2015
NM State; College of Agricultural, Consumer and Environmental Science, Lepidium latifolium:
Follow us on these social media sites:
The Basin and Range Project
We love the Basin and Range region and work to promote appreciation and respect for the area. We encourage all users to learn about, play in and protect this amazing resource.
We currently focus primarily on issues in the Nevada region of the Basin and Range, but are looking to expand soon.
We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.