Roots usually 1 per node, gray, 1-1.5 mm diam., villous and thicker when in contact with substrate, glabrous when aerial. Stems 4-8 mm diam., thick, smooth, internodes to 20 cm. Leaves with at least some persistent, fleshy; blade to 8 cm, margins somewhat involute, apex hooked. Inflorescences axillary, 15-flowered racemes, short-pedunculate, to 9 cm excluding peduncle; floral bracts broadly ovate, 2-13 mm, fleshy. Flowers: sepals and petals distinct and free, light green; dorsal sepal narrowly oblong-elliptic, slightly concave, 4.8-5.5 × 0.8-1.2 cm, apex obtuse to acute; lateral sepals elliptic-oblanceolate, slightly falcate, 4.5-5 × 0.9-1.3 cm; petals narrowly oblong-oblanceolate, abaxially keeled, 4.1-5 × 1.1-1.4 cm, apex acute; lip arching over column, reddish purple, becoming very pale at margin edge and within throat, broadly obovate, obscurely 3-lobed, 4-5 × 4-5 cm when spread, margins basally involute; claw and basal margins adnate to column for more than 1/2 its length, free portion crenulate; disc with broad thickened midrib extending length of lip, distal 1.5 cm of midrib with erect, scattered, thick, sometimes forked hairs, 1-2.5 mm, with hinged, stiff beard ± 1 cm at middle of disc midrib, midrib glabrous proximal to beard; disc flanking midrib glabrous but with numerous short fleshy hairs extending to lateral margins of throat, within 5-10 mm of apical margin; column arched, slender, 3.2 cm; pollinia yellow; pedicellate ovary 4.7-5 cm. Berries pendent, green, darkening at maturity, fusiform-clavate, 16 × 1.2 cm.

Flowering May--Jun. Hammocks; 0--20 m; Fla.; West Indies.

Vanilla dilloniana is known in the flora from Paradise Key, Everglades National Park, Miami-Dade County, Florida (P. M. Brown 2002).