Ontario Weeds: Common burdock
Excerpt from Publication 505, Ontario Weeds,
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Table of Contents
- Other Names
- General Description
- Stems and Roots
- Flowers and Fruit
- Similar Species
- Related Links
Name: Common burdock, Arctium minus
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.
Burdock, first-year rosette.
Burdock, second-year plant beginning to flower.
Common burdock. A. Rosette of leaves.
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
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.
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