1 Plant erect or trailing (but not twining), herbaceous or woody.

..2 Plant a woody shrub or trailing woody vine.

....3 Plant rhizomatous, suffrutescent, < 4 dm tall; leaves narrowly to broadly ovate; flowers blue, lavender, or white

....3 Plant erect, > 4 dm tall; leaves either lanceolate or elliptic; flowers yellow, white, pink, or red.

......4 Flowers yellow; shrub 4-12 dm tall, with only a few wand-like branches; [very rare waif in our area]

..2 Plant an herb or trailing herbaceous vine.

........5 Flowers with conspicuous or less conspicuous corona; follicles not paired; seeds with coma present

..........6 Plant wither an erect herb or a decumbent herb with stiff, thick stems (> 4 mm in diameter); leaves various, but not both petiolate and heart-shaped

..........6 Plant a trailing herbaceous vine with weak, thin stems (<2 mm in diameter); leaves petiolate and heart-shaped, 2-4 cm long

........5 Flowers lacking corona; follicles paired (occasionally single by abortion); seeds with coma absent (Catharanthus, Amsonia) or present (Apocynum).

............ 7 Leaves alternate (rarely a few on a plant subopposite)

............ 7 Leaves opposite.

............ ..8 Flower < 8 mm across; paired follicles pendent, 10-22 cm long; seeds with coma; mature plants normally > 7 dm tall

............ ..8 Flower > 20 mm across; paired follicles erect, 1.5-2.5 cm long; seeds lacking coma; mature plants 2-6 dm tall

1 Plant twining, herbaceous or woody.

............ ....9 Leaves cordate at base, ovate to broadly lanceolate, < 4× as long as wide.

............ ......10 Plants in flower.

............ ........11 Petals white; gynostegial corona > ¾ as long as the corolla lobes

............ ........11 Petals purple-black, brown, yellow, yellow-green, cream, or maroon (white in Matelea baldwyniana); gynostegial corona < ½ as long as the corolla lobes.

............ ..........12 Corolla lobes glabrous on the outer surface; dorsal anther appendages laminar; carpels smooth and angled

............ ..........12 Corolla lobes glandular-puberulent or puberulent on the outer surface; dorsal anther appendages absent; carpels muricate (Matelea) or smooth (Vincetoxicum).

............ ............ 13 Corolla lobes (5-) 6-18 mm long, purple-black, brown, maroon, yellow, yellow-green, cream, or white

............ ............ 13 Corolla lobes, 1.5-4.5 mm long, purple-black, brown, or maroon

............ ......10 Plants in fruit.

............ ............ ..14 Follicles muricate

............ ............ ..14 Follicles smooth and angled.

............ ............ ....15 Leaves cordate, broadly rounded, tapering abruptly to an acute, obtuse, or apiculate apex

............ ............ ....15 Leaves deeply cordate, tapering steadily to an acuminate apex.

............ ............ ......16 Corona a fleshy, lobed cup

............ ............ ......16 Corona nearly as long as to longer than the corolla lobes

............ ....9 Leaves not cordate at base (cuneate, rounded, or truncate); leaves ovate, lanceolate, or linear, > 1.5× as long as wide.

............ ............ ........17 Leaves linear, the margins parallel.

............ ............ ..........18 Leaves petiolate; calyx lobes deltoid, obtuse, ca. 1 mm long; leaves petiolate, not reflexed, often caducous; follicle 1-3 mm in diameter; [of se. SC and southwards]

............ ............ ..........18 Leaves sessile; calyx lobes lanceolate, acute, (1.3-) 1.5-2.5 mm long; leaves sessile, reflexed, persistent; follicle 6-7 mm in diameter; [of ne. NC and southwards]

............ ............ ........17 Leaves not linear, instead ovate or lanceolate (rarely deltoid/rhomboid shaped).

............ ............ ............ 19 Flowers brownish-purple

............ ............ ............ 19 Flowers primarily white, whitish-green, or creamy yellow.

............ ............ ............ ..20 Flowers with a corona; greenish-white

............ ............ ............ ..20 Flowers lacking a corona, white to creamy yellow.

............ ............ ............ ....21 Corolla lobes 3-4 mm long, acute, reflexed, pale yellow; leaves subcoriaceous; [native, common]

............ ............ ............ ....21 Corolla lobes 8-12 mm long, rounded, spreading, white; leaves coriaceous; [alien, commonly planted, rarely persistent or spreading]

1 Leaves tiny, bract-like, triangular, 6-14 (-17) per node

1 Leaves either needle-like, scale-like, or flattened and large, (2-) 3-4 (-6) per node.

..2 Leaves needle-like or scale-like, terete, angled, or flat in ×-section, < 2 cm long; leaves (2-) 3-4 (-6) per node

..2 Leaves flat, > 3 cm long; leaves (2-) 3 per node; [Eudicots].

....3 Plant a subshrub, < 3 dm tall, with < 10 leaves per stem.

......4 Leaves entire, broadly elliptic; flowers numerous, in a hemispherical head, subtended by 4 large white bracts

......4 Leaves serrate, narrowly ovate or narrowly obovate; flowers (1-) 2-8 in a long-peduncled umbel or corymb, not subtended by bracts

....3 Plant a shrub or tree, > 3 dm tall, with many > 10 leaves per stem.

........5 Leaves toothed, and most leaves also lobed

........5 Leaves entire, not lobed.

..........6 Leaves cordate at base; leaves about as long as wide; medium to large tree.

............ 7 Flowers white to yellow; capsules linear, >10× as long as wide; leaf undersurface with curly simple hairs; nectar glands present in the main vein axils on the undersurface of the leaf (visible from the underside or the upperside in fresh leaves and herbarium specimens as a triangle 1-4 mm on a side)

............ 7 Flowers lavender; capsules ellipsoid, < 2× as long as wide; leaf undersurface with branched (dendritic or stellate) hairs; nectar glands absent

..........6 Leaves cuneate to rounded at base; leaves > 1.5× as long as wide; shrub to small tree.

............ ..8 Leaves rounded at the tip

............ ..8 Leaves acute to acuminate at the tip.

............ ....9 Leaves lanceolate (> 2.5× as long as wide), the secondary venation not prominent; inflorescences axillary or terminal; flowers pink or white.

............ ......10 Inflorescences axillary; flowers pink; leaves thin and herbaceous; [native plants of wetlands]

............ ....9 Leaves ovate (< 2× as long as wide), the secondary venation prominent and arching-parallel; inflorescences terminal; flowers white, greenish-yellow, red, or orange.

............ ........11 Flowers in a spherical or hemispherical head; corollas white or greenish-yellow

............ ........11 Flowers in a monochasial helicoid cyme; corollas red to orange