Virginia Tech Weed Identification Guide

Common Burdock: Arctium minus

Weed Description:  A biennial that produces a rosette of very large leaves in the first year and a branched stem with many burs during the second year.  Found across the upper half of the United States and is most commonly found as a weed of pastures, hay fields, and fence rows.
Seedling:  Cotyledons are egg-shaped and widest near the apex (obovate) with a waxy surface.  Young leaves are also egg-shaped, except at the truncated base.

Roots:  Large taproot.

Leaves:  Rosette leaves are broadly heart-shaped, 6-18 inches long, 4-14 inches wide, with hollow petioles and wavy and toothed margins.  The undersides of these leaves are loosely hairy and light green.  Stem leaves are much smaller, alternate, and egg-shaped.
Flowers:  Occur in clusters at the ends of branches (terminal racemes) or in clusters that arise from the region between the stem and leaves (axillary racemes).  Flowers are purple to lavender, occasionally white, with outer bracts that are "hooked."  Flowers dry to a bur, and the hooked bracts are often confused with a thistle.
Fruit:  An achene, mottled dark-gray to black, 4-7 mm long, with a pappus of short bristles.

Stems:  Produced during the second year of growth.  Stems are erect, branched, hollow, hairy, and ridged. Stems may reach 5 ft in height.

Identifying Characteristics:  Large basal rosette of leaves with hollow lower petioles, and flowers with hooked bracts.   After senescence, the remaining burs on the stems of common burdock may resemble a thistle.  However, the dried flowers of thistle plants do not have hooked bracts like common burdock.