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| 1 Erect woody shrub to 2 m tall; stems hollow |
| 1 Trailing or twining vine; stems solid or hollow. |
| ..2 Corolla salverform, the long narrow tube cylindrical (with sides more-or-less parallel) for most of its length, the limb abruptly flaring at the summit of the tube. |
| ....3 Corolla 3-14 cm long, lavender to white; flowers open from evening until early morning. |
| ......4 Leaves tomentose beneath; corolla mostly white on the outer surface, lavender to purple on the inner surface, thus bicolored in-and-out; [of outer Coastal Plain dunes, hammocks, and shell middens from se. NC southward] |
| ......4 Leaves glabrous beneath; corolla either white on both surfaces or lavender on both surfaces, not bicolored in-and-out; [weedy, widespread, of disturbed habitats]. |
| ........5 Corolla 10-14 cm long, white |
| ........5 Corolla 3-7 cm long, violet or lavender |
| ....3 Corolla 2-4 cm long, scarlet, orange or yellow; flowers open from early morning to late morning or late afternoon. |
| ..........6 Leaf blade pinnately divided into 11-31 (or more) linear segments (with parallel sides) |
| ..........6 Leaf blade entire, or angled, or lobed into 3-7 lanceolate or ovate segments (broadening towards their bases). |
| ............ 7 Sepals acute to obtuse, the tip sometimes with a mucro; [s. peninsular FL] |
| ............ 7 Sepals acute, at least the 2 outermost with caudate tips; [collectively widespread]. |
| ............ ..8 Inner sepals 4-6 mm long; pedicels becoming reflexed in fruit; leaves usually unlobed (though sometimes with a few coarse dentate teeth) |
| ............ ..8 Inner sepals 2-3 (-4) mm long; pedicels remining erect in fruit; leaves usually 3-lobed about halfway from margin to base |
| ..2 Corolla funnelform to campanulate, the short to long tube expanding in diameter upwards from below the middle, the limb gradually to abruptly flaring at the summit of the tube. |
| ............ ....9 Pedicels and peduncles with spreading, ascending, or reflexed trichomes; gynoecium 3-parted; [Pharbitis clade] |
| ............ ......10 Sepals soft-pilose on the outer surface with slender trichomes |
| ............ ......10 Sepals hispid-pilose on the outer surface, with swollen-based trichomes. |
| ............ ........11 Sepals with slightly narrowed green tips shorter than to slightly longer than the body of the sepal; corolla pink (rarely white or blue); sepals oblong-lanceolate, obtuse or acute; leaves entire or 3–5-lobed |
| ............ ........11 Sepals with very narrow elongate green tips much longer than the body of the sepal; corolla blue with a white tube (drying pink): sepals ovate with an elongate apex, notably accrescent in fruit; leaves usually 3-lobed. |
| ............ ..........12 Sepals < 2 cm long at anthesis, abruptly narrowed upwards, the long subacute tips strongly spreading or recurved outwards; corolla < 3.5 cm long; peduncles very short. |
| ............ ..........12 Sepals ca. 3 cm long at anthesis, gradually narrowed upwards, the long acute tips suberect, straight, scarcely spreading; corolla 4–4.5 cm long; peduncles long or short |
| ............ ....9 Pedicels and peduncles glabrous or with short, appressed trichomes; gynoecium 2-parted. |
| ............ ............ 13 Stems trailing, rooting at the nodes; leaf apex emarginate, truncate, or obtuse; [of beaches from se. NC southward]. |
| ............ ............ ..14 Corolla lavender; larger leaves not lobed (though notched at the apex on at least the larger, better-developed leaves) |
| ............ ............ ..14 Corolla white with a yellowish or purple eye; larger leaves 3-7-lobed |
| ............ ............ 13 Stems erect or twining, not rooting at the nodes (except sometimes in I. batatas); leaf apex acute to acuminate; [collectively of various habitats, not beaches, widespread]. |
| ............ ............ ....15 Leaves palmately dissected with 5 (-7) lobes, the sinuses to within 2 mm of the petiole summit or the midvein. |
| ............ ............ ......16 Leaves pinnately dissected (the pair of lobes about the basal pair diverging from the midvein several mm above the basal pair); axillary buds developing stipule-like leaves |
| ............ ............ ......16 Leaves palmately dissected; axillary buds not developing leaves |
| ............ ............ ....15 Leaves entire or pinnately lobed. |
| ............ ............ ........17 Leaf base sagittate |
| ............ ............ ........17 Leaf base cuneate to cordate. |
| ............ ............ ..........18 Corolla 1.5-2.5 cm long, white or lavender |
| ............ ............ ............ 19 Corolla white; anthers purple; sepals lanceolate; capsule 10-15 mm in diamter; seeds 5-6 mm long |
| ............ ............ ............ 19 Corolla lavender; anthers white; sepals oblong; capsules 5-6 mm in diameter; seeds 2.8-3.0 mm long |
| ............ ............ ..........18 Corolla 3-8 cm long, at least partly pink to lavender (sometimes entirely white in I. batatas). |
| ............ ............ ............ ..20 Sepals ovate to oblong-elliptic; corolla usually white on the limb, the throat purple; anthers 5-7 mm long |
| ............ ............ ............ ..20 Sepals oblong-ovate to oblong-lanceolate; corolla usually pink to lavender on the limb, the throat lavender to purple; anthers 1.5-3.2 mm long. |
| ............ ............ ............ ....21 Sepals unequal in length, oblong-ovate, with acute to caudate apices; leaves mostly 10-15 cm wide |
............ ............ ............ ....21 Sepals more-or-less equal in length, oblong-lanceolate, with acuminate apices; leaves 2-5 cm wide |