Ohio Perennial and Biennial Weed Guide

Family:

Sunflower Family (Asteraceae)

Other Names:

Lappa minor, bardane, beggar's buttons, beggar's lice, burdock, burs, clotbur, cockle-button, cockleburs, cuckold dock, cuckoo-button, hardock, hurr bur, lappa, lesser burdock, love leaves, personata, petite bardane, smaller burdock, stick button, sticktight, thorny bur, wild burdock, wild rhubarb.

Origin and Distribution:

Common burdock originated in Europe and was likely brought to North America by early French and English colonists. By 1663, it was so widespread in the U.S. that a botanist mistakenly referred to it as a native species. Common burdock can be found throughout the U.S., with the exception of a few states along the southern border, and in southern Canada. In Ohio, the weed is most common in the eastern 2/3 of the state where it inhabits uncultivated areas such as roadsides, stream banks, waste places, abandoned farmsteads, and pastures. Common burdock grows in a wide range of soils from sandy clay to moist loam. The species prefers nitrogen-rich soils.

Plant Description:

Common burdock is a biennial that grows as a rosette of leaves the first year and then produces a 5-foot-tall, erect, bushy flowering stem. Rosette leaves are distinctive due to their large size, heart-shaped base, wooly undersurface, and hollow leaf stalks (petioles). Stem leaves are similar to but smaller than rosette leaves. Located at the ends of branches or at leaf axils on the flower stem are flower heads comprised of a bur with hooked bristles beneath a closely packed cluster of tubular, purplish flowers. The weed is best known for the hooked bristles on its burs that stick to fur and clothing. The only means by which common burdock reproduces are its seeds.

• Root System:

  The root system is a very large, thick, fleshy taproot that has a brown, corky, shredded surface.

• Seedlings and Shoots:

  First to emerge are two leaves (cotyledons) that are large, spoon-shaped, and have a waxy surface. Subsequent leaves are alternate, egg-shaped, flocked with short hairs, puckered between the veins, and bitter tasting. Attached to each leaf is a flared stalk (petiole) that clasps the basal stem of the rosette.

• Stems:

  During the rosette stage of growth, the stem remains compressed and close to the soil surface. As flowering is initiated, the stem elongates producing an erect flower stem that is 2- to 6-feet tall, much-branched, rough-hairy, hollow, and grooved lengthwise or angular.

• Leaves:

  The large rosette leaves are 20 inches long, 12 inches wide, and attached to the stem by way of hollow petioles that may be purple-tinged. The upper leaf surface is dark green and coarse while the underside is pale gray-green and wooly. Rosette leaves have a heart-shaped base and wavy edges. Stem leaves are alternate (1 leaf per node). Lower stem leaves resemble rosette leaves except they are smaller. Leaves gradually become smaller, less heart-shaped, and tapered at both ends as their location progresses up toward the tip of the stem. Also, their petioles become shorter and solid rather than hollow.

• Flowers:

  Each flower head consists of bristles with hooked tips that form a round, 3/4-inch-wide bur beneath a closely packed cluster of many individual, tube-shaped, reddish-purple flowers. Flowers appear alone or grouped on short stalks attached to the end of main branches or at leaf axils on the stem.

• Fruits and Seeds:

  In each bur are many single-seeded, 1/4-inch-long, brown, oblong, angular fruits having a short, stiff bristle at one end.

Similar Species:

Cotyledons of common burdock and giant ragweed (Ambrosia trifida) are similar, but giant ragweed cotyledons are smaller. As young seedlings, broadleaf dock (Rumex obtusifolius) and curly dock (Rumex crispus) can be confused with common burdock except they do not have hairs on the underside of the leaves. As a rosette, common burdock resembles cultivated rhubarb (Rheum rhabarbarum), but the leaves of rhubarb do not have wooly undersides and its petioles are solid and tinged red. Common burdock flowers are similar to those of bull thistle (Cirsium vulgare), but bull thistle stems and leaves have spines and its leaves are deeply lobed. Great burdock (Arctium lappa) is similar in appearance to common burdock except it grows to 9 feet tall, has larger flower heads arranged in flat-topped clusters, and the petioles of its rosette leaves are not hollow.

Biology:

During the first year, common burdock grows slowly and it is not uncommon for a rosette to consist of only a couple of leaves. Rosette leaves die over winter, so new basal leaves form in spring. Flowering stems emerge in June. Flowers form from July to October. Plants usually flower during the second year, but sometimes the flowers do not emerge until the third or forth year of growth. When burs dry, their hooked bristles attach to fur or clothing and the bur separates from the plant thereby dispersing its seeds. Dispersal of burs and seeds begins in September and continues throughout winter and into the following spring. A single plant produces 15,000 seeds on average, but yields of 200,000 to 400,000 seeds have been reported. Common burdock is associated with several microorganisms that cause powdery mildew (infects cucurbits and composites like lettuce, sunflower, and Chrysanthemum) and root rots (infecting many species including cotton and sugarbeets). The plant does not tolerate frequent cultivation.

Toxicity:

Common burdock is considered toxic due to potential diuretic effects, and there are reports of allergic reactions when the hooked bristles of burs lodge under the surface of the skin.

Facts and Folklore:

• The genus name Arctium was derived from the Greek word for 'bear' and likely refers to the scruffy, brown look of the burs.

• Common burdock fruit and roots were used to treat a variety of ailments ranging from coughs asthma, venereal diseases, rheumatism, lung and skin diseases, and scurvy.

• Velcro was inspired by the tiny hooks on the burs of this plant that stick to fur and clothing, similar to the sticky side of Velcro.

• Burs often stick to sheep reducing the value of the wool.

• The foliage can give milk a bitter taste if eaten in large enough quantities by cattle.

• Common burdock is reported to have a high mineral and vitamin content and is commonly found in health food stores in pill form.

• Native Americans used burdock roots as food in winter. The root of a related burdock species is widely cultivated in Japan as a vegetable and is known as 'gobo'.