Bushy annual with spiny burs that get tangled in fur and fabric.
Annual, moderately to much branched; leaf blades triangular or broadly ovate, green beneath; flower heads inconspicuous in sessile axillary clusters; flowers produce brownish or yellowish-brownish ellipsoid burs; found in moist, disturbed areas.
Habitat
Waste places, disturbed moist areas, fallow fields, sandy flood plains and shorelines, stream and river banks, margins of ponds and lakes; sandy and alkaline soils.
Flower Characteristics
Male flowers are tiny, in clusters at top of stem. Female flower heads are in leaf axils and form spiny, up to 1-1/2 inches long burs.
Leaf and Stem Characteristics
Triangular or broadly egg-shaped to circular or kidney-shaped, 1-1/2 to 7-1/2 inches long, 1 to 6 inches wide; surfaces rough-hairy, palmately veined; margins coarsely-toothed and un-lobed or with 3 or 5 shallow lobes; tip rounded or broadly pointed.
Fruit and Seed Characteristics
Fruits are cylindrical to barrel-shaped and hard, spiny burs; green drying to brown; burs can stick to fur and clothing and can be very difficult to extract.
Burs contain 2 seeds each in their own compartment. One of the seeds in each bur may germinate the following year with the other seed taking at least 2 years to germinate.