Portal | Wildflowers Home Page | Plant Books | 500+ Flower Photos | Edibles | Weed Ecology | Mushrooms | Links
Whitetop or Hoary Cress--Cardaria draba, C. chalapa, C. pubescens
Mustard Family
About Whitetop: The three species of whitetop differ in the shape of their seed pods. C. draba has the heart-shaped seed pods and is most common in Montana. C. pubescens has purplish, globe-shaped seed pods, and C. chalapa has lens-shaped seed pods. 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 in 1916. It now infests about 32,000 acres across the state.
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.
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.
Grazing: Like most members of the Mustard Family, whitetop contains 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. You can graze on the mustard-flavored seed pods too. Just rub the dried pods between your hands to knock the seeds loose and blow gently to separate the pods.
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. You must read the range ecology sections of this website before applying any tool of weed control. Return to the Wildflowers & Weeds Home Page for articles on Desertification and Noxious Weeds.
Notes
Return to the Weed Profiles Table of Contents
Check out these books by Thomas J. Elpel
 Participating in Nature |  Botany in a Day |  Direct Pointing to Real Wealth |
 Living Homes |
Return to the Wildflowers & Weeds Home Page.
|  |
How to Place Retail Orders
Order On-Line: Order on-line with your Visa, Mastercard, Discover or American Express. Simply click on the links to learn more about each product and enter the quantity you want in the little white boxes, then click the "Add to Order" button. You will be transferred to our secure payment service for the final check-out.
Order by mail or telephone: We accept checks and money orders payable in US dollars. Please use the on-line shopping basket to tally your order. Click the "Pay for Order On-line" button to calculate the postage, then print or copy the information and call or send it to us at the address above.
Shipping Options
 |  |
| USA Customers We ship all USA orders via USPS Priority Mail, except as otherwise noted on the website. Express Mail shipping is available by special request. | International |
Granny's Country Store Departments
Tom's Books & Videos
Wilderness Survival | Nature, Wildlife, Tracking
Wildflowers and Edibles | Resources for Educators
Home-Building Resources | Goods for Green Living
Books & Gifts for Kids
Thomas J. Elpel's Web World Pages
Green University | Granny's Country Store | HOPS Press, LLC
Sustainable Living Skills | Primitive Living Skills
Wildflowers & Weeds | Society of Primitive Technology
Jefferson River Canoe Trail | What's New? | Search This Site!
Return to Thomas J. Elpel's
Web World Portal | Web World Tunnel
© 1997 - 2008 Thomas J. Elpel