2. Commelina communis L. (common dayflower)

Pl. 27 d, e; Map 103

C. communis var. ludens (Miq.) C.B. Clarke

Plants annual, the roots slender, fibrous. Stems erect to ascending or decumbent with age, 8B80 cm long, often rooting at the nodes. Leaf blades 2B12 cm long, lanceolate to narrowly ovate, glabrous to minutely scabrous on the upper surface, somewhat glaucous on the undersurface. Leaf sheaths mostly 1B2 cm long, glabrous or ciliate with white hairs near the tips. Inflorescences mostly stalked, the folded spathelike bracts 12B30 mm long, the margins free to the base, the lower edge (midrib of the bract) straight or nearly so. Sepals 3B4 mm long. Petals strongly unequal, the upper 2 petals 8B16 mm long, blue or less commonly purple, the lower petal 3B5 mm long, white. All 3 staminodes with well-developed false anthers, these mostly 4-lobed, yellow, lacking a reddish brown spot in the middle. Fruits 6B7 mm long, 2-locular and 4-seeded. Seeds 2.5B3.5 mm long, the surface with a usually strongly developed pattern of reticulate, polygonal ridges. 2n=36B90. MayBOctober.

Introduced, common throughout Missouri (native of eastern Asia, a nearly worldwide weed widely naturalized in the U.S.). Disturbed alluvial ground along rivers and streams, ditch banks, cultivated fields, gardens, moist roadsides, and railroad embankments.

Several varieties of C. communis have been accepted by some previous authors. Steyermark (1963) discussed the presence of two such taxa in Missouri. The common var. communis is said to have blue upper petals 10B15 mm long, leaf sheaths glabrous, and the anthers and false anthers of the staminodes all yellow; var. ludens has purple upper petals 8B10 mm long, leaf sheaths ciliate with white hairs near the tips, and the anthers and false anthers of the staminodes with a purplish brown spot in the middle. Tucker (1989) noted that plants attributed to the two varieties have differing susceptibility to the smut Ustilago commelinae (Kom.) Zundel in the northeastern United States, suggesting an underlying biological basis to the separation of these taxa. However, in Missouri, there appears to be poor correlation between the morphological characters said to differentiate them. Plants with purple petals are uncommon and sporadic throughout the state, but sometimes have all yellow anthers and false anthers. Most collections have at least some hairs on the leaf sheath margins, regardless of petal color. Thus the two varieties cannot be consistently characterized in the state and are not considered worthy of formal taxonomic recognition at the present time.

Although C. communis is mostly considered a weed by gardeners, it is infrequently cultivated as an ornamental. In some parts of the world, plants are cooked and eaten as a green vegetable.