Carolina or maroon Carolina milkvine, Carolina or maroon Carolina spinypod

Cynanchum carolinense Jacquin, Collectanea 2: 288. 1788; Gonolobus carolinensis (Jacquin) R. Brown ex Schultes; Odontostephana carolinensis (Jacquin) Alexander

Vines, herbaceous. Stems 1–2(–5), twining, 100–300 cm, hirsute with eglandular and incon­spicuous glandular trichomes. Leaves with 2 colleters on each side of petiole; petiole 1–9 cm, hir­sute with eglandular and inconspicuous glandular trichomes; blade ovate to orbiculate, 3–20 × 1.5–18 cm, base shallowly to deeply cordate, with 2–4 lam­inar colleters, apex acute to acuminate, surfaces hir­sute with eglandular and inconspicuous glandular trichomes. Inflorescences solitary, simple or compound, umbelliform to racemiform, extra-axillary or terminal, pedunculate, 3–30(–40)-flowered; peduncle 1–13 cm, hirsute with eglandular and inconspicuous glandular trichomes. Pedicels 3–30 mm, hirsute with eglandular and inconspicuous glandular trichomes. Flowers: calyx lobes spreading, ovate to elliptic to lanceolate, 1.5–4.5 mm, apex acute to acuminate, hirsute with eglandular and inconspicuous glandular trichomes; corolla pale maroon to yellowish green tinged with maroon abaxially, dark maroon, dark brown, or dark purple (yellow and maroon or yellow with maroon tinge at base), with a cream to light rose (maroon) ring at base of corona adaxially, reticulate markings only apparent on yellow forms, rotate to campanulate, tube 1–2 mm, lobes spreading to erect or somewhat reflexed, sometimes twisted, oblong, 4–15 mm, margins plane (reflexed), minutely hirtellous abaxially, glabrous adaxially; corona united to column near base, of 5 united, fleshy segments, each with 2 lateral lobes at apex exceeding the medial lobe, forming a sheath that equals or slightly exceeds style apex, adaxial appendages incurved, incumbent on anthers, sometimes concealed when corolla lobes erect, maroon (orange-yellow or green-yellow), 0.7–2 mm, 2–3 mm diam., glabrous; apical anther appendages bright white with yellow to maroon patch at base, rhomboid; style apex pink to maroon, pentagonal, flat. Follicles not striate, lance-ovoid to nearly fusiform, 7–13 × 1–2.5 cm, apex acuminate, sparsely to moderately muricate, minutely hirsute. Seeds brown, ovate (orbicular), 8–9 × 6–8 mm, margins broadly winged, chalazal end entire, faces rugose; coma 2.5–3.5 cm.

Flowering Apr–Jul(–Aug); fruiting Jun–Oct(–Nov). Hill slopes, bluffs, ridges, flats, valleys, streamsides, ditches, rock outcrops, limestone, sandstone, gabbro, serpentine, sandy and loamy soils, talus, cedar glades, barrens, oak woods, oak-hickory, oak-pine, mixed-hardwood, pine-mixed hardwood, pine, and riparian forests, old fields, secondary woods, pine plantations; 0–700 m; Ala., Del., D.C., Ga., Ky., La., Md., Miss., N.C., S.C., Tenn., Va.

Matelea carolinensis is a widespread and variable species that has long presented challenges in circum­scription. The most widely distributed and common form has small, nearly rotate corollas with deltate to oval corolla lobes that are sometimes reflexed. However, Appalachian populations in the Carolinas may vary by having larger flowers with lobes that are much narrower and ascending. In the Appalachian region, there is a bewildering array of floral diversity including large and small corollas with ascending lobes and individual plants with lobes that are reflexed, spreading, and ascending, perhaps in part due to developmental changes. Plants from the Carolinas with large corollas and ascending lobes have been considered to be conspecific with those in the Ozark region treated here as M. decipiens since that species was first described by Alexander. These two population systems are strongly disjunct. Careful study of corona structure suggests that these populations are convergent in their narrow, campanulate corollas and that the Appalachian plants belong to the same species as the widespread populations with smaller, rotate corollas with which they intergrade. Further study using population genetics and other data types is needed to address conflicting treatments of these plants. As currently understood, M. carolinensis occurs almost entirely east of the Mississippi River with only a few isolated occurrences in Louisiana west of the river (for example, Thomas 13,124 [TENN] from Catahoula Parish). Conversely, M. decipiens occurs entirely west of the river. Matelea carolinensis has suffered habitat loss at the northern edge of its range. It is presumed to be extirpated in the District of Columbia and is uncommon and of conservation concern in Delaware, Kentucky, and Maryland. Reports from Pennsylvania and West Virginia have not been confirmed and probably represent misidentifications of M. obliqua.