Stems terete, sparsely hairy, (bark not corky). Leaves not pungent, glabrous or subglabrous to short-hairy, not soft-hairy; stipules linear-subulate, 2–5 × 0.5–1 mm, eglandular; petiole glandular, glands cuplike; blade roughly symmetric, 2–7 × 2.5–16 cm, as wide as to usually wider than long, 3–9-lobed, primary lobes 3 and often further lobed, lobes acute, middle primary lobe much shorter than to ± as long as lateral 2 primary lobes, margins entire; abaxial fine veins moderately to prominently raised, abaxial nectaries usually absent, sometimes present near leaf margins but not forming lines. Floral bracts obscure, linear-subulate, 1 × 0.2–0.5 mm, margins entire, eglandular. Flowers: floral tube absent; sepals green, 6–10 × 2–4 mm; petals absent; corona filament whorls 2, outer filaments purple basally, yellow apically, or yellow throughout, linear, terete to slightly transversely compressed, 3–7 mm. Berries dark blue to black, globose to dorsiventrally compressed, 6–12 × 6–12 mm. 2n = 24.

Flowering Apr–Aug(–Dec). Open oak-juniper or coastal woodlands and savannas, grasslands and semideserts, primarily over limestone; 30–900 m; Tex.; Mexico (Coahuila, Nuevo León, Tamaulipas).

E. P. Killip (1938) and W. C. Martin and C. R. Hutchins (1980) incorrectly indicated that Passiflora tenuiloba is native to New Mexico. This is based upon the misinterpretation of confusing labels on old specimens (see D. H. Goldman 2004).

Passiflora tenuiloba has the most variable leaves of any species in the genus. They vary considerably in texture, color, indument, lobe length and number, and petiole-gland size and shape, not only between populations but also within individual plants.