Ontario Weeds: Common burdock

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Excerpt from Publication 505, Ontario Weeds, Order this publication

Table of Contents

  1. Name
  2. Other Names
  3. Family
  4. General Description
  5. Stems and Roots
  6. Flowers and Fruit
  7. Habitat
  8. Similar Species
  9. Related Links

Name: Common burdock, Arctium minus (Hill) Bernh.,

Other Names: petite bardane, Burdock, Burs, Clotbur, Lesser burdock, Wild burdock, Wild rhubarb, bardane mineure, rapace, rhubarbe sauvage, toques

Family: Composite or Aster Family (Compositae

General Description: Biennial, reproducing only by seed.

Photos and Pictures

Burdock, first-year rosette.
Burdock, first-year rosette.
Burdock, second-year plant beginning to flower.
Burdock, second-year plant beginning to flower.

Common burdock.
Common burdock.

Common burdock. A. Rosette of leavfes.
Common burdock. A. Rosette of leaves.
B. End of flowering branch.
B. End of flowering branch.

Stems & Roots: Stems erect, 60-180cm (2-6ft) high, often widely branched, thick, hollow, grooved lengthwise; first leaves in a basal rosette, becoming large (up to 50cm, 20in. long, and 30cm, 12in. wide), with heart-shaped base, coarse, resembling a clump of cultivated rhubarb, but the undersides of the leaf blades are white woolly and the stout leafstalks are hollow; lower leaves on the stem of second-year plants similar to basal leaves, smaller, alternate (1 per node); middle and upper leaves gradually smaller with shorter, slender stalks and the blade tending to be less heart-shaped and more pointed towards both ends, especially among the flower heads.

Flowers & Fruit: Flower heads globular, numerous, borne singly on short stalks or in small clusters at ends of branches and from axils of leaves; each head about 2cm (4/5in.) in diameter, densely covered with purplish, hooked bristles; ray florets absent; disk florets purple or occasionally white, closely packed in the centre of the head; at maturity the head or bur (hence the common name "burdock") easily breaks off its stalk and clings to clothing and animal fur, gradually scattering the brownish angular seeds, each about 6mm (1/4in.) long. Flowers from July to September.

Habitat: Common burdock occurs throughout Ontario in waste places, pastures, open woods, roadsides, fencerows and barnyards but seldom in cultivated land.

Similar Species: It is distinguished by its rosette of very large heart-shaped leaves resembling Rhubarb but woolly on the undersurface and with hollow leafstalks, and its tall, branched stem in the second year with many short-stalked flower heads or burs densely covered with hooked spines and borne singly or in small clusters at ends of stems and from leaf axils, these turning brown at maturity.

Related Links

... on general Weed topics
... on weed identification, order OMAFRA Publication 505: Ontario Weeds
... on weed control, order OMAFRA Publication 75: Guide To Weed Control

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