2n = 72

Rhizomatous, usually glabrous, perennial herb; stems slender. Leaves 3-foliolate; leaflets sessile, glossy green or tinged bronze, glabrous, broadly obovate-cuneate, (1-) 3-6 (-8) mm long, with 1-3 lobes, and each lobe with 1-4 shallow crenate teeth; leaflets produced early in the growing season and leaflets of reduced plants often entire or with 2-3 shallow crenate teeth; petioles glabrous or, very rarely, with a few retrorse hairs near blade, slender, (2-) 15-50 (-100) mm long; stipules scale-like. Umbels simple, (1-) 2-7-flowered; peduncles about equalling leaves; bracts scale-like, usually fused, sometimes free almost to base, 0.5-1 mm long; flowers hermaphrodite, shortly pedicellate, c. 2-3 mm diam. Fruit light brown, (1.5-)2-2.5 × (1-)1.2- 1.8 mm, rounded on dorsal edge; ribs slightly engraved into surface of mature fruit.

Folia 3-foliolata; foliola glabra, obovato-cuneata, 1-8 mm longa, plerumque 2- vel 3-lobata, lobis crenatis, raro integris vel simpliciter crenatis; petioli plerumque glabri, raro pilos paucos retrorsos laminam versus gerentes. Umbellae simplices, (1-) 2-7-florae; flores hermaphroditi circa 2-3 mm diametro. Fructus 1.5-2.5 mm latus, 1-1.8 mm longus; costae in fructus maturi superficiem leviter sulcatae. Differt a H. tripartita foliolis glabris, fructus costis manifeste sulcatis; differt quoque a H. hydrophila foliolis plerumque magis profunde lobatis et umbellulis plerumque flores plures gerentibus.

Usually glabrous perennial, forming small to large patches; stems slender. Lvs 3-foliolate; leaflets sessile, glossy green or bronze-tinged, usually glabrous, very rarely with a few scattered hairs, broadly obovate-cuneate, (1)-3-6-(8) mm long, with 1-3 lobes and each lobe with 1-4 shallow crenate teeth; leaflets produced early in the growing season and leaflets of reduced plants often entire or with 2-3 shallow crenate teeth; petiole usually glabrous, very rarely with a few retrorse hairs near blade. Umbels simple, (1)-2-7-flowered; peduncles ± = lvs. Fls shortly pedicellate. Fr. glabrous, (1.5)-2-2.5 × (1)-1.2-1.8 mm, rounded on dorsal edge; ribs slightly engraved into surface of mature fr.