Categories
BLOG

white top weed

White top weed

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.

Notes

  • Thomas J. Elpel. Botany in a Day. HOPS Press: Pony, MT. January 2000.
  • Roger L. Sheley and Jack Stivers. “Whitetop”. MSU Extension Service Publication #EB 138. 1996, 1998.

Cardaria draba, C. chalapa, C. pubescens: Whitetop, Hoary Cress: It’s characteristics and history, plus alternative weed control strategies.

Network Center

Whitetop (Hoary Cress)

Noxious Weed Season Battle Opens In Earnest With Focus On Whitetop (Hoary Cress) Control
Read our recent Press Release

The Strategy: This noxious weed occurs sporadically throughout the valley. It is an escaped perennial ornamental that was originally brought in as a ground cover. The plant grows less than 18 inches in height. Multiple branches grow off of the root system and each has white flowers at its terminal end which appears as a carpet of white. It has an integrated root system that allows it to creep into unwanted places and spreads if roots are carried in the soil. Leaves are light green with a distinctive white midvein.

The Attack: This perennial plant is one of the first noxious weeds to appear in the spring, with a quick formation of white buds. The plant has rhizomatous roots (spreading) that allow the plant to spread into lawns, established plantings, and even push up roadways. Since it occurs early and develops very thick canopies, it easily chokes out desirable plants, and its diverse root system allows the plant to absorb most of the water and nutrients.

The Defense: Mechanical control is not very effective. Many people that dig, disk, or plow this plant notice it comes back with a vengeance in a few weeks. No biological control insects are available for this plant. There is one class of herbicides that work well: one ounce of Telar or Escort during the budding stage will grant the landowner 98 percent weed control. Opensight is another product that works well. These products are very safe to use in a pastures and one does not have to remove the livestock during application. 2,4-D and Roundup will only set the plant back a few weeks.

ERADICATING WHITETOP

PLEASE NOTE – The proper use and application of herbicides can be an effective way to control and eradicate noxious and invasive plants. Before using herbicides, always carefully follow the label and safety instructions on the label. While we recommend the use of herbicides as one of the effective tools for integrated pest management, the Idaho Weed Awareness Campaign assumes no liability for herbicide applications.

For more information, click on the link below to download the Idaho’s Noxious Weeds Control Guidelines publication produced by the University of Idaho Extension.

Network Center Whitetop (Hoary Cress) Noxious Weed Season Battle Opens In Earnest With Focus On Whitetop (Hoary Cress) Control Read our recent Press Release The Strategy: This