Common burdock (Arctium minus) is one of four burdock species that have been introduced into North America. Common and great burdock (Arctium lappa) are the two weedy species. Common burdock is found in many areas and this has resulted in a plant with many names. In fact, in early publications there was confusion in the nomenclature of this species (Gross, et al. 1980). Some of its many identities include lesser burdock, wild burdock, petite bardane, beggar’s buttons, cockle button, hardock, hurr-bur, cuckold dock, stick button, clot bur, and wild rhubarb.
Common burdock is native to Eurasia but is now naturalized in North America (USDA 1970). It is native to and reached North America with early English and French settlers. Common burdock was included on a list of “such plants which are common with us in England” in the mid 1600’s (Gross, et al. 1980). Both common and giant burdock were found long ago in North America; however, in the early North American literature giant burdock was more often sited than common burdock. There are reports that common burdock was widespread in Pennsylvania by the mid 1800’s. The Native Americans of Western Washington saw common burdock as being recently introduced in the 1930’s. Thus its spread across the country from New England perhaps took 200 to 300 years (Gross, et al. 1980).
Common burdock survived very well in its new North American home, as seen by its wide distribution across North America. It is throughout all of the United States except approximately the southern border and areas around the Great Lakes (USDA 1970).
Every providence of Canada has common burdock; it is most abundant in southeastern Canada. In its native home its range includes most of continental Europe to areas in Scandinavia, eastern Turkey, and upward into Finland (Gross, et al. 1980).
Common burdock is a biennial, thus completing its life cycle in two years. However, a study at Michigan State University found that, “Arctium minus plants generally take 4 or more years to flower under field conditions with moderate to high densities of grasses and herbaceous dicots” (Gross and Werner 1983). If conditions throughout the second year are poor, many plants labeled as biennials will not flower (Gross, et al. 1980). Different reports indicate flowering times from June to August, July to October, and July to September. In Wisconsin the most common flowering time is mid July to the first frost. It appears that common burdock fertilizes more by an allogamy system, even though it does have potential to be autogamous. Insects are attracted to common burdock, even though it has no odor, and help to fertilize the plants (Gross, et al. 1980).
Most seeds germinate in early spring; cold treatment of the seeds is not necessary. A study on the germination of common burdock was done by mixing fresh seeds with a shallow layer of soil. They were stored in a container below ground level and cultivated 3 times/year to assess seed survival and the seasonal distribution of seedling emergence. Few seeds of A. minus persisted for more than two years (Roberts and Neilson 1981). The weed seen longevity of common burdock in one report is listed as 10-20 years (Chipenda 1982). One report shows that “seedling emergence and survival were reduced by the presence of litter and vegetation” (Gross and Werner 1983). The number of seeds produced per head varies greatly. Large differences have been found within a site, between sites, in the same year and across years. A two year study in Ontario found that common burdock averaged 11,700 and 13,400 seeds per plant. (Gross, et al. 1980). Seeds are mature by September and are spread until the following spring. Research done on seed bank populations show them to be small and patchy (Gross, et al. 1980).
There is outcrossing and occasional hybridization in common burdock, as well as great variation in the natural populations. Taxonomists recognize up to eight species of burdock. Common burdock is more variable in Europe than it is in North America. Seven subspecies and five varieties were found in Europe while three forms under the subspecies are in North America.
- A. minus f. pallidum with white petals of the corollas
- A. minus f. purpureum with deep purple corollas
- A. minus f. laciniatum Clute with sterile flowers and leaves narrow and laciniate (Gross, et al. 1980).
Common burdock is found in places where the soil is not disturbed; therefore, it is not commonly found in cultivated areas. This is due to the fact that it is a biennial, so it needs areas that are not severely disturbed on an annual basis. Such areas include: farmlands, pastures, waste places, open or disturbed woods, road sides, fence rows, barnyards, abandoned fields, and stream banks. F. Swink has stated that common burdock, “is especially common in weed patches where there has been previous cultivation or extensive abuse by livestock” (Gross, et al. 1980). It is found both on moist fertile soils, many with high soil nitrogen content, and on sterile clay soils. Common burdock can be found as an isolated plant or in large patches; these patches are due to a large input of seeds near parent plants. Many times, not many other plants grow around the patch; some think this is a result of the large leaves that reduce light at ground level (Gross, et al. 1980).
As common burdock is found in such diverse areas, it is no surprise that it is spreading and in some areas it is listed as an invasive species. The Wisconsin Department of Natural Resourses Bureau of Endangered Resources listed common burdock in a column under the heading: “Listed below are exotic and native species that are potentially threatening to Wisconsin native habitats. They either already exist in the state or have become serious problems in other parts of the Midwest. They may become troublesome in Wisconsin in the future. Some are already nuisances in wild lands in the state. Land managers and others interested in maintaining stable native plant populations should watch for these potentially problematic species and attempt to control them before they become a serious threat” (Hoffman and Kearns 1997).
In the past common burdock has seldom been considered a serious weed in crops because it can be well controlled by cultivation (Gross, et al. 1980). As more farmers have adopted no-till farming, this plant is becoming more important and can cause economic yield losses if not controlled. There are other areas of economic importance with common burdock. The value of wool is reduced when the dry heads of the plant cling to the coats of animals (Steyermark 1963), thus it has been listed as a serious threat to sheep (Fortnet 1996). Also, if cows eat large quantities of it, the plant gives a bitter taste to the milk (Georgia 1931).
Many microorganisms grow on common burdock, and two microorganisms have economic importance. Powdery mildew (Erysiphe cichoracearum DC. ex Merat) affects such species as squash and cucumbers as well as many species of composites, including Dahlia, Helianthus, and Chrysanthemum. Root rot (Phymatotrichum omnivorum (shear) Dug.) attacks cotton and sugar beets, and as many as 1700 other plant species (USDA 1953, 1960; Westcott 1971).
Common burdock has long been used as an medicinal herb. There is a long list of ways in which burdock is helpful in maintaining the health of the human body. “As an alterative and depurative, burdock is one of the most effective herbs for cleansing the blood without the side effect of nausea. It contains 27-45% inulin as well as an abundance of iron. As a blood purifier, it is used for arthritis, rheumatism, sciatica, and lumbago. Burdock can help to reduce joint swelling and calcification deposits. It promotes kidney function and also helps to remove toxins through the seat glands. The energy is cooling; therefore, it is used for “hot”/yang conditions such as fevers, boils, styes, carbuncles, and infections. Burdock helps metabolize carbohydrates. Use with sassafras to soothe the hypothalamus; aids the pituitary gland to adjust hormones and body weight” (American Health and Herbs 1997). Preparations made from the root, leaves, and fruits may be used to treat coughs, asthma, gout, and may serve as laxatives and diuretics. However, it has been listed as a poisonous plant because of its diuretic effects (Woodcock 1925). The bristles of the plant also may cause localized allergic reactions for some individuals. Common burdock is edible, however, the root of great burdock is more commonly used as a vegetable. Although not used much as a food source, The USDA listed common burdock as being “in reasonably constant demand as a medicinal herb” (Sievers 1930).
Roots The root system consists of a long, thick, and fleshy taproot. With time, it may become very tough and hard.
Stem Common burdock’s stem is a crown, close to the ground, the first year. The second year it is much branched, from two to six feet tall, hairy, and somewhat grooved or angular.
Leaves The first year a basal, dense rosette is formed. All rosette leaves die back during the winter. The rosette needs vernalization; however, one report shows that some plants flower sporadically after several years of growth without vernalization. The rosette is a competitive plant in that its long-petioled, broad leaves shade the surrounding area, thus leading to openings for the colonization of burdock seedlings. The second year new leaves are formed and the leaves are distributed alternately on the stem with the larger leaves near the base. The leaves are large with a heart-shaped base. They are hairy and coarse, resembling a clump of cultivated rhubarb. The undersides of the leaf blades are white and woolly, and the stout leaf stalks are hollow. The middle and upper leaves get gradually smaller and have shorter, more slender stalks and are more pointed towards both ends.
Flower Heads Small red-violet, very rarely white, disk flowers surrounded by numerous hooked bracts, or spines, make up the flower head. The flower heads are globular and numerous and borne singly on short stalks or in small clusters at ends of branches and from axils of leaves. They are 1.5-3 cm in diameter and the disk flowers are surrounded by numerous hooked bracts that later form a bur, about 1.4 cm in diameter.
Seeds The head, or bur, of the flower breaks off and scatters the seed. Many times it gets attached to clothing or animal fur thus dispersing the seed. The seeds themselves are dark gray to brownish, 0.25 inches long, and rough.
Many practices and herbicides maintain and control common burdock; therefore, with timely weed management activities, common burdock should be relatively easy to control. The following herbicides were listed as having excellent control on common burdock: 2,4-D, MCPA, 2,4-DB, and dicamba. Glyphosate is listed as having good control (Klingman, et al. 1983). For soybeans, 2,4-D ester applied no less than seven days before planting should prove effective. 2,4-D can be used in corn with preplant, pre and post options. Pre plant treatmetns must be applied 7-14 days before planting. Roundup as a burnddown treatment in no-till systems or in glyphosate-resistant crops gives acceptable burdock control. Thorough cultivation should kill most burdock plants. Mowing may prove to be effective method of control as a study in Michigan showed that “defoliated plants generally produced fewer seeds/head, fewer heads/plant and fewer seeds/plant” (Reed and Stephenson 1972, 1973).
There are 13 insect species which attack the common burdock plant. Burdock moth (Metzneria lappella) is the only one that has been reported in North America. This insect greatly reduces the number of viable seeds in the plant, thus it may be a regulatory factor that influences both the distribution and abundance of the common burdock populations. There are no active programs exploring this biological control measure in Wisconsin.
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* Student Assistant, Dept of Agronomy, University of Wisconsin-Madison