Oldfield milkvine, climbing milkweed

Odontostephana decipiens Alexander in J. K. Small, Man. S.E. Fl., 1077. 1933; Gonolobus decipiens (Alexander) L. M. Perry

Vines, herbaceous. Stems 1(–5), twining, 50–200 cm, hirsute with eglandular and inconspicuous glandular trichomes. Leaves with 2 colleters on each side of petiole; petiole 1.5–9.5 cm, hirsute with eglandular and inconspicuous glandular trichomes; blade ovate to oval to orbiculate, 4–14 × 2.5–16 cm, base shallowly to deeply cordate, with 2 laminar colleters, apex acute to acuminate, surfaces hirsute with eglandular and inconspicuous glandular trichomes. Inflorescences soli­tary or paired, simple or compound umbelliform, extra-axillary, pedunculate, 10–40-flowered; peduncle 1–9 cm, hirsute with eglandular and inconspicuous glandular trichomes. Pedicels 10–25 mm, hirsute with eglandular and inconspicuous glandular trichomes. Flowers: calyx lobes spreading, elliptic to lanceolate, 2–3.8 mm, apex acute to acuminate, hirsute with eglandular and inconspicuous glandular trichomes; corolla pale maroon to green tinged with maroon abaxially, purple to maroon (greenish yellow or green tinged) adaxially, not reticulate, shallowly campanulate, tube 1.5–2.5 mm, lobes erect to spreading, slightly twisted, oblong, 7–18 mm, margins plane (recurved), glabrous abaxially, minutely hirtellous at base to glabrate adaxially; corona united to column near base, usually pentagonal, of 5 united, laminar segments, each with 2 lateral lobes at apex equaling or exceeding medial lobe, forming a ring exceeded by style apex, adaxial appendages incurved, incumbent on anthers, sometimes concealed by erect corolla lobes, maroon, 0.8–2 mm, 3–4 mm diam., glabrous; apical anther appendages bright white with pink to maroon patch at base, rhomboid; style apex yellow-green to maroon, pentagonal, flat. Follicles not striate, lance-ovoid, 8–12 × 1–2 cm, apex acuminate, moderately muricate, minutely hirsute. Seeds brown, ovate, 7–8 × 5–6 mm, margins broadly winged, chalazal end entire, faces rugose; coma 3–4.2 cm.

Flowering Apr–Jul(–Sep); fruiting Jun–Oct. Rocky and sandy soils, limestone, dolomite, granite, hill slopes, ridge tops, bluffs, valleys, stream banks, sandhills, pine and pine-oak forests, cedar glades; 20–400 m; Ark., Kans., La., Mo., Okla., Tex.

Matelea decipiens is distributed entirely west of the Mississippi River as far as presently known. Its range extends across the Ozark Mountains to the Gulf Coastal Plain in Louisiana and eastern Texas. However, it is largely absent from the western Ozarks in southwestern Missouri and northwestern Arkansas and from the Ouachita Mountains, where it is replaced by M. baldwyniana. Matelea decipiens reappears at scattered locations west of the Ozark uplift in Oklahoma and southeastern Kansas in Neosho County. It is considered to be of conservation concern in Kansas, and its status in Oklahoma and Texas merits evaluation. There are no known sites where M. decipiens and M. baldwyniana co-occur. The flowers of M. decipiens become smaller as the range of M. hirtelliflora is approached in Texas, and they barely overlap with that species (corolla lobes 7–18 mm in M. decipiens versus 3.2–7.5 mm in M. hirtelliflora). The corollas of M. decipiens are never hirtellous adaxially, as they very often are in M. hirtelliflora. E. J. Alexander (1933) and all subsequent authors considered some populations of spinypods in the Appalachian region to belong to this species, based on large, maroon corollas with ascending lobes. Appalachian populations are considered to belong to 15. M. carolinensis, as discussed under that species.