Whitetop or Hoary Cress Hoary Cress. Lepidium draba (formerly known as Cardaria draba) Lens-podded Whitetop. Lepidium chalepense (formerly known as Cardaria chalepensis)
Hairy Whitetop. Lepidium appelianum (formerly known as Cardaria pubescens) Mustard Family | By Thomas J. Elpel with additions by Pamela G. Sherman
About Whitetop: The three species of whitetop differ in the shape of their seed pods. Hoary cress (Lepidium draba) has the heart-shaped seed pods and is most common in Montana. It is also known as Whitlow Grass. Hairy whitetop (L. appelianum) has purplish, globe-shaped seed pods, and lens-podded whitetop (L. chalepense) has lens-shaped seed pods, as the name implies. A related, similarly invasive species is perennial pepperweed, (L. latifolium), also called Cardaria latifolia. These plants are native to the Middle East and the former USSR. The weed seeds were probably brought to this country with contaminated alfalfa seed. Whitetop was first identified in Gallatin County, Montana in 1916. It has spread to about 32,000 acres across the state. It may be more prolific in other western states.
Whitetop favors disturbed soils with moderate moisture, especially road-sides, ditch banks, sub-irrigated pastures and rangeland. Irrigation water can be screened to prevent seed dispersal to fields. A single plant can spread to an area 12 feet in diameter in its first year by sending up shoots via lateral underground stems, called rhizomes. Once established, a patch may continue to spread at 2 to 5 feet per year. Each plant can produce 1,200 to 4,800 seeds. The seeds are only viable in the soil for about two years.
Edibility: As all mustards, this early season plant has been traditionally eaten as a spring green. Add a few leaves to a salad for a spicy mustard flavor. Some prefer to cook whitetop in one or two changes of water (3-5 min. each). Please see the forager blogs Hunger and Thirst for Life, as well as Wild Food Girl for recipes and discussions of a potential safety concern.
According to the Plants for a Future database, "young leaves and shoots [are eaten] raw in salads or cooked as a potherb. A report says that the young leaves contain the toxin hydrogen cyanide, though does not give any more details. In small quantities this substance is fairly harmless, and has even been recommended as having health benefits, but caution is suggested if you eat these leaves. The pungent leaves are used as a seasoning. The seed is used as a condiment, it is a pepper substitute." [Plants for a Future]. Rub the dried pods between your hands to knock the seeds loose and gently blow to separate the pods. Add the seeds to a salad or any dish for flavoring, or grind them and add vinegar and oil to make mustard paste.
Other early wild mustards are perhaps more delicious, such as the related perennial pepperweed, (Lepidium latifolium), as well as creasy greens, aka bittercress, (Barbarea spp.) (two changes of water makes it delicious), blue mustard (Chorispora tenella), and field pennycress, (Thlaspi arvense).
Mechanical Controls: Hand-pulling is only minimally effective because the plants regenerate from the roots. The roots must be removed and the site diligently monitored for plants that may emerge from root fragments. Cultivation is impractical in most cases, since the soil must be re-cultivated within 10 days of weed emergence throughout the growing season for 2 to 4 years. Mowing reduces seed production, but does not kill the plants. However, mowing can enable better targeting of herbicides.
Hand pulling of above ground plant parts is ineffective. Successful hand pulling or digging requires complete plant removal within 10 days after weed emergence throughout the growing season for two to four years. Hand pulling and digging can be a useful method for controlling new introductions of white- top in riparian areas and around the home. Removing whitetop is best accomplished when the soil is moist.
Grazing: All plants of the Mustard family are edible to some degree, although they may contain varying amounts of glucosinolate glycosides (See Botany in a Day) which may interfere with the body's ability to absorb iodine if taken in excess. Supplemental iodine may be fed to livestock to help prevent complications, and alternate forage must be available, especially for young or lactating stock. Few actual grazing studies have been done on these plants. Whitetop is considered nutritious, but coarse and bitter when mature. Sheep graze on it in the early growth stage, and cattle eat the seed pods. Much to my surprise, our horses willingly grazed it to the ground early in the season, before and during the bloom. As shown in the photo, I ran the electric fence through the whitetop patch for comparison. Inside the pasture the horses ate it down to nothing. With a little attention and well-timed grazing, whitetop need not become a serious problem!
Seeding: Whitetop can be out-competed by dense stands of perennial grasses or legumes like alfalfa.
Chemical Controls: Whitetop can be difficult to kill because of its deep and regenerative root system. At least the seeds are short-lived, so a treated site only needs to be monitored for a few years. 2,4-D is effective early in the season, before budding. Chlorsulfuron (Telar® 75) or metsulfuron (Escort®) can be applied during the budding or early bloom stages. Picloram (Tordon® 22K) has little effect on whitetop. Whitetop often grows in dense stands where less toxic non-selective herbicides might be used, combined with a revegetation program.
Important: Most "weed problems" are really "people problems" from poor land management and a lack of ecological insight. It is easy to reach for a tool like fire, mowing, or herbicides to attack an out-of-control weed, but often those tools do little to get to the root cause of the weed infestation, and sometimes make the problems worse. Please read more about range ecology, desertification, and invasive weeds on this website before applying any tool of weed control Go to: Desertification and Invasive Weeds.