3. Commelina diffusa Burm. f.

Pl. 27 g; Map 104

Plants annual (perennial farther south), the roots slender, fibrous. Stems decumbent to ascending, 8B80 cm long, often rooting at the nodes. Leaf blades 2.5B8.0 cm long, lanceolate, glabrous to minutely scabrous. Leaf sheaths mostly 0.5B1.0 cm long, ciliate with white hairs near the tips. Inflorescences mostly stalked, the folded spathelike bracts 10B24 mm long, the margins free to the base, the lower edge (midrib of the bract) curved and noticeably arched. Sepals 3B4 mm long. Petals strongly unequal, the upper 2 petals 7B10 mm long, blue, the lower petal 3B5 mm long, blue. Two of the 3 staminodes with well-developed false anthers, these 4B6-lobed, yellow, lacking a reddish brown spot in the middle. Fruits 4.0B6.3 mm long, mostly 3-locular and 5-seeded. Seeds 2B3 mm long, the surface with a strongly developed pattern of reticulate, polygonal ridges. 2n=28B60 (2n=30 in the U.S.). JulyBOctober.

Scattered nearly throughout the state, although more common in the southern counties (nearly worldwide, but questionably native in the New World). Mudflats and gravel bars along rivers and streams, margins of lakes and ponds, disturbed alluvial ground, and openings in bottomland forests; also in cultivated fields and untended lawns.

For a discussion of the separation of this species from C. caroliniana, see the treatment of that species. The geographic origin of C. diffusa is poorly understood, and many botanists question whether it is truly native in North America. In Missouri, the species has many similar ecological characteristics of introduced weeds, but its presence in the state during the early 1800s suggests that it may represent a disturbance-adapted native, much like some species of Amaranthaceae and Chenopodiaceae.