Sp. Pl. 1: 41. 1753.
Herbs, annual. Roots thin, rhizomes short, subterranean, bearing cleistogamous flowers produced from base of plant. Stems ascending to decumbent or occasionally scrambling. Leaves: leaf sheaths, not auriculate, often with red hairs at summit; blade ovate to lanceolate-elliptic, (1–)2–9(–11) × 1–3(–4.5) cm, apex rounded, obtuse or acute, pubescent. Inflorescences: distal cyme often exserted and 1-flowered, sometimes vestigial; spathes often clustered, subsessile (peduncles 1–3.5 mm), funnelform, 0.5–1.5(–2) cm, margins connate basally, pubescent. Flowers: chasmogamous flowers bisexual and staminate, subterranean cleistogamous flowers bisexual; petals of staminate flowers all blue (rarely lilac), proximal smaller; lateral stamen filaments not winged; staminodes 2–3; antherodes yellow, cruciform; pollen white; medial stamen pollen yellow. Capsules 3-locular, 2-valved, 4–6 mm. Seeds 5, brown or blackish, seeds of adaxial locule 1.7–2.5 mm, shallowly reticulate, farinose. 2n = 22.
Phenology: Flowering spring–fall.
Habitat: Citrus plantations, fields, yards, and other cultivated and disturbed sites
Introduced; Calif., Fla., Ga., La., neotropics, native, paleotropics.
Commelina benghalensis was first recognized and collected in California in 1980. The California plants are approximately hexaploid and represent a separate and much later introduction than the southeastern plants. The species is federally listed as an Obnoxious Weed.