A much-branched, hairy annual, with flat-topped clusters raised well above the foliage. Flowers on long stems (peduncles), white, in umbels (umbrella-like clusters), minute, with 5 sepals and 5 petals. Blooms June–September. Leaves alternate and usually also basal, 1 or 2 times feather-compound, resembling parsley. Fruit densely covered with hooked prickles and cling to clothing and fur.
Height: to 2½ feet.
Scattered to common statewide.
Habitat and Conservation
Introduced; native of Eurasia. Occurs on banks of streams and rivers, disturbed portions of glades, upland prairies and savannas, and degenerating clear-cuts in mesic upland forests; also roadsides, railroads, old fields, and open, disturbed areas. It was first collected in Missouri in 1909 and has become much more abundant in recent decades as it spreads along roadsides and railroads.
Humans literally pave the way for the spread of many weedy species when we bulldoze the earth to build roads. Fast-growing weeds quickly colonize the disturbed, bare soil and rapidly produce multitudes of seeds. Slow-growing plants take longer to become established.
The bristly seeds cling to the fur and feathers of animals (and clothing of humans). This carries the seeds away from the parent plant and establishes populations in new areas. This may be how this plant came to Missouri in the early 1900s.