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| 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] |
| ......4 Flowers white, pink, or red; shrub 10-40 dm tall, much branched from the base; [commonly cultivated in our area (and sometimes persistent), particularly near the coast] |
| ..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] |