Ipomoea batatas (L.) Lam. is the cultivated sweet-potato (often called "yam," a name more strictly applying to the monocot genus Dioscorea).

1. Corolla salverform, red, with stamens and pistil conspicuously exserted; sepals with subulate subterminal appendages; leaves deeply and ± palmately divided into narrow lanceolate segments.

I. × multifida

1. Corolla funnelform, blue to purple or white, with stamens and pistil shorter; sepals various; leaves not divided or only broadly 3-5-lobed.

2. Stems glabrous or nearly so; sepals obtuse to rounded, at most hispidulous toward margin beneath (more uniformly hispidulous above).

I. pandurata

2. Stems pubescent; sepals acute or acuminate, with long stiff hairs beneath, especially toward base.

3. Calyx ca. 17-25 mm long, the sepal lobes narrowed to prolonged linear-acuminate tips; peduncles rarely as long as calyx (flowers often nearly sessile).

I. hederacea

3. Calyx ca. 11-15 (-16) mm long, the sepal lobes ± oblong and acute; peduncles longer than the calyx.

I. purpurea