Erect perennial 3-10 dm tall; stems strongly ribbed, glabrous to hirsutulous.
Leaves twice pinnate, 3-10 cm long; pinnae 6-12 pairs, 1.5-4 cm
long; leaflets very small, oblong, 2-5 mm long, 0.5-1 mm wide, ciliolate,
mucronate; stipules setaceous, 5-10 mm long. Inflorescence a small
globose cluster of minute flowers; peduncles 2-6 cm long. Flowers
whitish to greenish, regular; calyx campanulate, 5-toothed; corolla
of 5 petals, separate or slightly united at the base; stamens 5, distinct,
long-exserted. Fruits in a dense, subglobose head, flat, strongly curved,
1-2.5 cm long, 4-7 mm wide, containing few to several seeds. Late Jul--Sep.
Uncommon and confined to sandy or gravelly lake shores in the n part of our
region, becoming more common and occupying a variety of habitats in the c and
s parts; (OH to ND, s to FL, TX and NM).