Including Asclepiadaceae of Michigan Flora.

A primarily tropical family with a number of species that are sources of chemicals useful in medicine and as poisons. In all our native species, the fruit (a follicle) splits open to release seeds bearing a tuft of long silky hairs; the sap of most species is a milky latex.

1. Plant a prostrate, trailing subwoody evergreen creeper; flowers solitary in leaf axils; corolla blue, with limb (1.5-) 2-3 cm broad; seeds glabrous.

Vinca

1. Plant erect or a twining climber; herbaceous; not evergreen; flowers in terminal or axillary cymes or umbels; corolla greenish, white, pink, orange, yellow, red, purple to almost black, less than 1 cm broad; seeds with tuft of silky hairs.

2. Plant a climbing vine, strongly twining at least apically; corolla lobes spreading or ascending.

3. Corolla lobes purple to nearly black, leaves rounded to subcordate at base.

Vincetoxicum

3. Corolla lobes white, leaves deeply cordate.

Ampelamus

2. Plant erect or ascending, not twining; corolla lobes strongly reflexed at maturity, except in Apocynum, white, pink, purple, yellow, orange, or greenish.

4. Corolla lobes erect to spreading; flowers in small terminal (and sometimes axillary) cymes; mature fruits 3-5 mm in diameter.

Apocynum

4. Corolla lobes strongly reflexed at maturity; flowers in umbels; mature fruits 6-35 mm in diameter.

Asclepias