Commelina erecta L.
Family - Commelinaceae
Habit - Annual forb with somewhat thickened, fibrous roots.
Stems - Ascending to erect, to 90 cm, multiple from base, sometimes rooting at lower nodes, glabrous to sparsely pubescent near apex, often branching.
Leaves - Alternate, simple, entire, 4-15 cm long, linear to narrowly ovate, usually sparsely pubescent, sometimes somewhat glaucous on the undersurface. Leaf sheaths mostly 1-3 cm long, ciliate with white hairs, the tips extended past the attachment of the leaf blade with rounded, usually spreading auricles of tissue.
Leaf sheath and auricles.
Inflorescence - Mostly near the tips of the stems, short-stalked, the folded spathelike bracts 12-25 mm long, the margins fused in the lower third, the lower edge (midrib of the bract) straight or nearly so Spathe often scabrous due short, stiff hairs.
Arrow shows joined base of spathe.
Flowers - Sepals 3-4 mm long. Petals 3, strongly unequal, the upper 2 petals 10-25 mm long, blue, the lower petal 5-7 mm long, white. All 3 staminodes with well-developed false anthers, these 4-6-lobed, yellow, lacking a reddish brown spot in the center. Stamens 3, with one incurved and having a larger anther. Anthers yellow, 4-lobed. Filaments glabrous, pale yellow to white, to 4 mm long. Style curling at apex, to 5 mm long, glabrous, white. Ovary green, 1 mm in diameter, 3-locular.
Dorsal view, floral organs.
Fruits - Capsules 4-6 mm long, 3-locular and 3-seeded. Seeds 3-4 mm long, the surface smooth to slightly granular.
Flowering - May - October.
Habitat - Sand and gravel bars, streambanks, wooded slopes, bluffs, glades, roadside ditches.
Origin - Native to U.S.
Lookalikes - Commelina communis, other members of the genus.
Other info. - This pretty and distinctive native species is most common in the southern
half of Missouri, though probably found at least scattered throughout the state. Its U.S. distribution encompasses most of the continental
states except a few in the northwestern region. It is easily recognized by general appearance, though there are some closely related lookalikes.
This species is defined by having two blue and one white petal, and a partially fused bract subtending the inflorescence. The bract
fusion is easily disrupted, so it is best to look carefully without touching, or look for the "elbow" on the rear of the bract
rather than a smooth arc (see image above). A third detail is that the false anthers on the three staminodes are entirely yellow
without a central brown spot.
Steyermark and other authors recognized various infraspecific forms based on leaf width or spathe size. These show substantial
intergradation and are not formally recognized at present. The genus name commemorates two Dutch botanists, Jan and Kaspar Commelin,
who had a brother who died at an early age and contributed nothing to botany. The three petals of the flower represent these three brothers.
Steyermark and other authors recognized various infraspecific forms based on leaf width or spathe size. These show substantial intergradation and are not formally recognized at present. The genus name commemorates two Dutch botanists, Jan and Kaspar Commelin, who had a brother who died at an early age and contributed nothing to botany. The three petals of the flower represent these three brothers.
Photographs taken in Winter Haven, FL., 6-27-02, and at Millstream Gardens Conservation Area, Madison County, MO., 7-17-04 (DETenaglia); also at Holly Ridge Conservation Area, Stoddard County, MO, 8-15-2009, Klondike County Park, St. Charles County, MO, 8-8-2011, at the "racetrack" sand prairie, Scott County, MO, 8-30-2011, and along the Katy Trail, Warren County, MO, 8-2-2012, 9-4-2015, 7-11-2016, and 8-3-2015 (SRTurner).