Climbing or limerock milkvine, northern spinypod

Cynanchum obliquum Jacquin, Collectanea 1: 148. 1788; Odontostephana obliqua (Jacquin) Alexander; Gonolobus obliquus (Jacquin) R. Brown ex Schultes var. shortii A. Gray; Matelea shortii (A. Gray) Woodson

Vines, herbaceous. Stems 1(–5), twining, 100–300 cm, hirsute with eglandular and inconspicuous glandular trichomes. Leaves with 2 colleters on each side of petiole; petiole 1–7 cm, hirsute with eglandular and inconspicuous glandular trichomes; blade ovate to oblong or elliptic (lanceolate, orbiculate), 3.5–15 × 2–13 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 or paired, umbelliform (rarely compound), extra-axillary, pedunculate, 5–15(–20)-flowered; peduncle 1–9 cm, hirsute with eglandular and incon­spicuous glandular trichomes. Pedicels 5–40 mm, hirsute with eglandular and inconspicuous glandular trichomes. Flowers: calyx lobes spreading, elliptic to ovate (nar­rowly deltate), 2–4.5 mm, apex acute to acuminate, hirsute with eglandular and inconspicuous glandular trichomes; corolla pale maroon to yellowish green tinged with maroon abaxially, pink, reddish, or maroon (green, cream, or orange), with a cream to rose ring at base of corona adaxially (ring sometimes absent), not reticulate, rotate-campanulate to campanulate, tube 0.5–1.5 mm, lobes erect to spreading, twisted (coiled), oblong to linear, 8–16 mm, margins reflexed to plane, minutely hirtellous with glandular and eglandular trichomes abaxially, glabrous adaxially; corona united to column near base, nearly circular, of 5 united, very fleshy segments, each with 2 lateral lobes at apex equaling or exceeding medial lobe, forming a sheath that equals style apex, adaxial appendages incurved, incumbent on anthers, sometimes concealed when corolla lobes erect, cream to rose to maroon, 1–2 mm, 5 mm diam., glabrous; apical anther appendages bright white with maroon patch at base, truncate; style apex cream to rose to maroon, pentagonal, flat. Follicles not striate, lance-ovoid, 10–15 × 1.5–3 cm, apex acuminate, moderately muricate, sparsely and minutely hirsute. Seeds brown, ovate (orbicular), 7–9 × 4–6 mm, margins broadly winged, chalazal end entire, faces rugose; coma 2.5–3.5 cm.

Flowering (Apr–)May–Sep(–Oct); fruiting Jun–Oct. Rocky or fine soils, limestone, dolomite, sandstone, shale, hill slopes, bluffs, ridge tops, valleys, stream banks, oak and cedar woods, oak-hickory and mixed-hardwood forests, old fields, glades, barrens; 50–900 m; Ala., D.C., Ga., Ill., Ind., Ky., Md., Miss., N.C., Ohio, Pa., Tenn., Va., W.Va.

Matelea obliqua has a wide range across the Appalachian Mountains and Cumberland and Allegheny plateaus, extending into the Ohio River Valley and upper Gulf Coastal Plain, but it is common only in a few local areas. It is most common in Kentucky and Tennessee and locally in Madison County, North Carolina. The range barely enters several states, where M. obliqua is uncommon and is (or should be) considered to be of conservation concern, especially in Alabama (Calhoun and Madison counties) and Georgia (Catoosa and Floyd counties). Records outside the documented range are based on misidentifications pertaining to M. carolinensis or M. decipiens. Typically, M. obliqua can be distinguished by reddish purple to reddish brown corollas (versus maroon to purple in those species), with long, narrow, twisted corolla lobes. The most reliable character is the thick corona ring that has a diameter greater than in any other species of the eastern United States spinypods.