Two varieties have been recognized: Commelina dianthifolia var. dianthifolia (Arizona, New Mexico, Texas), with the spathes gradually tapering into a long, acuminate apex, and C. dianthifolia var. longispatha (Torrey) Brashier (Arizona, Colorado, New Mexico), with the spathes abruptly narrowed below the middle into a long, attentuate tip (C. K. Brashier 1966). Although most U.S. specimens are readily separable into these taxa, their ranges and ecologies overlap very broadly in Arizona and New Mexico. Until their variation in Mexico is studied, I can see no useful purpose in maintaining these varieties.
Plant: Perennial herb; tuberous roots; STEMS erect to ascending, unbranched to sparsely branched Leaves: sheaths with purple veins, blade linear-lanceolate, 4-15 cm long, 0.4-1 cm wide, glabrous to puberulous, the margin scabrous, the apex acuminate INFLORESCENCE: solitary spathes, peduncles 1.5-9.5 cm long, spathes 2.5-8 cm long, 0.7-1.7 cm wide, the margins free, scabrous, the surface green, often suffused and/or striped with purple, glabrous to puberulous, the apex acuminate; upper cyme usually 1-flowered Flowers: perfect or staminate; pedicels puberulous; petals dark blue, the lower ones ±not clawed; staminodes 3, yellow, cruciform Fruit: FRUITS 5-6 mm long, apiculate. SEEDS 5, brown, 2-2.5 mm long, 1.5-2 mm wide, rugose, pitted; SEEDS 1-5, testa rugose or smooth, tan to brown, hilum linear Misc: Open grassy meadows in ponderosa pine, oak and pinyon-juniper forest on granitic substrate; 1200-2900 m (4000-9500 ft.); Jul-Sep REFERENCES: Puente, Raul, and Robert B. Faden. 2001. Commelinaceae. J. Ariz. - Nev. Acad. Sci. Volume 33(1).
Puente and Faden 2001
Duration: Perennial Nativity: Native Lifeform: Forb/Herb General: Perennial herb with tuberous roots, stems erect to ascending, unbranched to sparsely branched. Leaves: Linear-lanceolate, 4-15 cm long, 0.4-1 cm wide, glabrous to puberulous, the margin scabrous, apex acuminate. Flowers: Solitary spathes, peduncles 1.5-9.5 cm long, spathes 2.5-8 cm long, 0.7-1.7 cm wide, margins free, scabrous, surface green, often suffused and striped with purple, glabrous to puberulous, apex acuminate; upper cyme usually 1-flowered; flowers perfect or staminate, puberulous pedicels with dark blue petals, lower ones not clawed; staminodes 3, yellow, cruciform. Fruits: Loculicidal capsules, 5-6 mm long, apiculate. Ecology: Found in open meadows, often on granitic soils; 4,000-9,500 ft (1219-2896 m); flowers July-September. Distribution: AZ, s CO, NM, swTX; south to s MEX. Notes: Distinguished from C. erecta by having a bract below inflorescence (spathe) which is not fused all the way to the base (back end or side towards the plant) where erecta is. Can be confused with Tradescantia but is differentiated by its solitary spathes (bracts subtending flowers) and flowers, while Tradescantia has an open umbellate inflorescence, rather than having a spathe. Additionally, Tradescantia has hairy stamen filaments. Ethnobotany: Taken as a strengthener by tuberculosis patients, and given to livestock as an aphrodisiac. Etymology: Commelina comes from the Dutch botanists Jan (1629-1692) and nephew Caspar (1667-1731) Commelijn, Editor: SBuckley, 2010, FSCoburn 2014