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