Dear Aggie: We have burdock on our property and the burrs get into my dog’s coat. How can I eliminate this weed?
A: From an evolutionary perspective, burdock species (both Arctium minus and Arctium lappa) are masters of spreading their seeds. Native to Europe, burdock has seed heads with prickly barbs that immediately catch onto an animal’s coat — or a gardener’s clothing — at the lightest touch. In fact, the inventor of Velcro was inspired by the tenacity of burdock seed-heads. As the animal moves about the environment, hitchhiking seeds shake loose from the burrs, spreading the plant into new locations. Unfortunately, as the seed heads break apart, they work their way into an animal’s coat and become difficult to remove. They are especially troublesome with long-haired breeds — from Scottish terriers to wool sheep to Highland cattle — and must be cut from the animal’s coat. The barbs can even work their way into the skin or into an animal’s eyes, resulting in infection.
Embedded burrs can cause dirt and moisture to buildup in an animal’s coat. In livestock kept outdoors during the winter, this buildup can compromise the animal’s ability to remain warm in freezing temperatures. Small birds have been reported to get caught in clusters of the burrs and slowly die.
Burdock is a biennial whose seeds emerge in early spring. A member of the Aster family, it grows in many settings, from nitrogen-rich barnyards to urban waste areas to disturbed woodlands. It has large leaves, some as long as 18 inches, that emerge from a central rosette. In the first year, the plant quickly grows a deep taproot, allowing it to pull nutrients and moisture from subsoils. The deep taproot gives the plant a competitive advantage over other species, allowing burdock to weather hot and dry conditions and dominate the garden. The taproots are also nearly impossible to pull up without digging. Interestingly, although extremely fibrous, the roots are edible and considered a delicacy in some Asian cultures. Purple flowers appear in its second year, which turn into troublesome seedpods (burrs) from midsummer onward.
Elimination of burdock is difficult. Watch carefully for newly emerging burdock seeds, generally from mid-April to early May. Simple cultivation or even flame-weeding can control seedlings in the cotyledon stage (when there are only two simple leaves). If you allow them to grow beyond this stage and establish a strong taproot, they will be difficult to remove. Individual plants can be dug up, but care must be taken to remove the entire taproot, which can be up to two feet in length. Mowing the plants will slow their flowering but is unlikely to kill them; they will quickly resprout and send up new flower stalks, sometimes only a few inches high.
Non-selective herbicides specifically labeled for use on broadleaf weeds are another option. These include products such as Roundup (glyphosate) and Burnout (a mixture of clove oil and citric acid). Herbicides should be applied early in the growing season. Repeated applications may be needed for older, established plants which will draw from reserves held in the taproot.
Keep in mind that you must follow all label instructions when using these products. Non-selective herbicides will also kill any plants that you might want to keep should the spray drift onto them. Those wishing to eliminate burdock from pasture or cultivated crops should consult Cooperative Extension staff for additional guidance.
Michael Nuckols is the agriculture and natural resources issues leader at Cornell Cooperative Extension of Jefferson County. Contact him at 315-788-8450 ext. 227 or firstname.lastname@example.org.