Burdock

The leaves on burdock plants are some of the largest you are likely to find, getting as large as 12 or 14 inches across. They are dark green, dull, and more or less heart-shaped. The plants vary in height from 1.5 feet to 10 feet tall. Flowers are small, lavender or pink, and similar in shape to thistle blossoms. In the fall, burdock plants produce burs about one inch in diameter. Fortunately, burdock plants are quite easy to control because they reproduce only by seed, and take two years to become mature plants. The first year, low-growing plants called rosettes are produced from seed. To control the plants at this point, an application of herbicide is probably easier than digging out the deep taproot. Several good herbicides for this purpose include Safer's Superfast Weed Killer, Finale, and Roundup. Superfast Weed Killer is simply a highly refined soap; it will kill only portions of the plant with which it comes in contact and will not translocate into the roots. If you use Superfast, apply it only to the pest plant because it will damage grasses and desirable plants also. Check the plant periodically in case regrowth is occurring from the roots. Finale is a synthetic herbicide derived from naturally-occurring bacterium, in a water base (no petroleum), low mammalian toxicity. Roundup is also a relatively safe herbicide, for both humans and the environment, when used as directed. Roundup will move down into root systems. After application, it does not move in the soil and it breaks down quickly. However, like Superfast, it will kill any plant it comes in contact with, including grass, trees, and shrubs. Products containing the herbicide 2,4-D can also be used to manage burdock. Spot application of these herbicides can prevent damage to desirable plants. Herbicide control of burdock is most effective on the first-year rosettes. To control mature plants, cut them down before flowers and burs are formed. This will prevent new seeds
from being produced. 

References: 

Pacific Northwest Weed Control Handbooks. 1997. Extension Services of Oregon State University. Corvallis, OR 97331-0817. 
Thomson, W.T. 1996. A Guide to Lawn, Garden, and Home Pest Control Products. Thomson Pubs., Fresno, CA 93791. 121 pp. 

Weed Control Guide. 1997. Meister Pub. Co. Willoughby, OH 44094-5992. 538 pp. 
Whitson, T., et al. 1991. Weeds of the West. Pioneer Printing, Jackson Wyoming. 630 pp. 

Written by Sherry Lajeunesse, Extension Urban Pest Management Specialist. Sept., 1997

Categories: Weed, Burdock

Date: 04/02/02