Also Known As: lesser burdock, wild burdock, wild rhubarb, beggsr’s button, bardane
Common burdock, (Arctium minus Bernh.), is a biennial that is native to Europe. In the plant’s first year, it forms only a rosette, similar in appearance to rhubarb. The rosette can reach 3 feet across, with leaves that are large, simple, heart-shaped, and wooly beneath. In its second year, the plant develops an erect, somewhat grooved, hollow stem that grows 3 to 7 feet tall and has multiple branches. The stem can be green or reddish-purple in color. While lower leaves are large and heart-shaped, upper stem leaves are smaller and tapered at both ends. Leaves are dark green and coarse above, and wooly- hairy underneath, with margins that are toothed or wavy.
Flowering occurs from July until frost. Flowers are purplish in color, numerous, and occur alone or in clusters, borne at the ends of branches or at leaf axils on the stem. Flower heads are about ¾ inch in diameter and are covered with spine-tipped bracts, the outer ones having hooked tips. Because of its spine- covered flower heads, the plant resembles a thistle. Mature flower heads dry, becoming burs with hooked bristles that cling to clothing and animal wool or hair, much like Velcro, which they are said to have inspired. The plant has a large, tough fleshy taproot. Common burdock reproduces by seeds, and a single plant produces 15,000 seeds on average.
Common burdock can be found throughout most of the United States. It occurs along roadsides and ditch banks, and in pastures and waste areas. The plant generally prefers moist, nitrogen-rich soils, but will grow in a variety of soils. Common burdock is known to host powdery mildew and root rot, which can infect certain cash crops and other plant species. Livestock willingly graze common burdock, but if grazed in large quantities, foliage of the plant can give milk a bitter taste. The burs of the plant can become matted in sheep’s wool, significantly reducing the quality and value of the wool.
The plant is considered toxic due to potential diuretic effects. In addition, leaves and stems of the plant contain lactones and may cause dermatitis in humans.
Common burdock is typically not a problem in crops since it does not tolerate cultivation. As with other plants that reproduce solely by seed, elimination of seed production and depletion of the seed bank should be the primary objective of an integrated plan to manage common burdock. Preventing dispersal of the burs is critical in reducing seed spread.
Physical/Mechanical: Small infestations can be pulled or hand dug, although removal may be difficult because of the plant’s large, tough taproot. Established plants will resprout if the whole root is not removed. Any existing seed heads should be bagged and removed from the site. Plowing or disking will kill small plants. Mowing or other cutting methods used prior to seed set will prevent seed formation.
Chemical: Common burdock can be effectively controlled by several available herbicides, such as glyphosate (non-selective herbicide), clopyralid, clopyralid + triclopyr, 2,4-D, aminopyralid, and picloram, generally to be applied between rosette and bloom stages.
More information can be found in the PNW Weed Management Handbook
USE PESTICIDES WITH CARE. Apply them only to plants, animals, or sites listed on the label. When mixing and applying pesticides, follow all label precautions to protect yourself and others around you. It is a violation of the law to disregard label directions. Store pesticides in their original containers and keep them out of the reach of children, pets, and livestock.
Biological: No biological control organisms are currently available. Livestock will willingly graze common burdock and may be effective for control if used as an integrated management tool.
Questions: contact Steve Van Vleet or phone (509) 397 – 6290
Photo credits included in pdf