Including Cuscutaceae of Michigan Flora.

1. Plants leafless, non-green, annual parasitic vines.

Cuscuta

1. Plants leafy, green, not parasitic.

2. Stigma at most with 2-3 small lobes; calyx ca. 6-23 mm long, fully exposed.

Ipomoea

2. Stigma deeply cleft into 2 lobes ca. 2.5-4 mm long; calyx less than 6 mm long or covered by two large bracts.

3. Calyx all or mostly covered by 2 large closely subtending bracts; corolla ca. 2.5-6.5 cm long; stigma lobes oblong-elliptic.

Calystegia

3. Calyx fully visible; corolla ca. 2.2 (-2.5) cm long or shorter; stigma lobes linear-filiform.

Convolvulus