Amer. Orchid Soc. Bull. 15: 331, figs. 1–7. 1946.
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 oblongelliptic, 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.
Phenology: Flowering May–Jun.
Elevation: 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).
"thick" is not a number.