Commelina communis L.

Dayflower, Asiatic Dayflower

Commelina communis plant

Family - Commelinaceae

Habit - Annual forb with slender, fibrous roots.

Stems - Erect to ascending or decumbent with age, to 80 cm, internodes glabrous, somewhat pubescent and often rooting at nodes.

Leaves - Alternate, entire, typically glabrous to minutely scabrous above, glaucous below. Base of blade forming a sheath around stem. Sheaths mostly 1-2 cm long, glabrous or ciliate with white hairs near the tips.

Commelina communis sheathLeaf sheath.

Inflorescence - Inflorescences axillary, mostly stalked, the flowers emerging from folded bract (spathe). Spathelike bracts 12-30 mm long, the margins free to the base, the lower edge (midrib of the bract) straight or nearly so.

Commelina communis spathe3Spathelike bract.

Commelina communis spatheSpathe divided to the base.

Flowers - Sepals 3-4 mm long. Petals 3, strongly unequal, the upper 2 petals 8-16 mm long, blue, the lower petal 3-5 mm long, white. Fertile stamens 3. Staminodes 3, with well-developed false anthers, these mostly 4-lobed, yellow, usually with a reddish brown spot at the center.

Commelina communis flower2Flower.

Fruits - Capsules 6-7 mm long, 2-locular and 4-seeded. Seeds 2.5-3.5 mm long, the surface with a usually strongly developed pattern of reticulate, polygonal ridges.

Commelina communis fruitsFruits.

Flowering - May - October.

Habitat - Banks of streams and ditches, moist roadsides, lawns, disturbed sites, railroads.

Origin - Native to Asia.

Lookalikes - Other members of the genus, especially Commelina erect.

Other info. - This plant is scattered to common throughout Missouri. Distribution maps suggest that it is probably more common than the native species (C. erecta) in the northern half of the state but less common in the southern half. Its larger range includes the eastern half of the continental U.S. and Canada. As a group, dayflowers are easily recognized by the "Mickey mouse morphology" of their flowers, with two large, blue upper petals like cartoon mouse ears. One of the native dayflowers, C. erecta, looks virtually identical except for the appearance of the folded bract enclosing the inflorescence. In the native species this is partially fused, with a visible elbow in the curve of the bract. In C. communis it is open to the base and smoothly curved (see photos above).

The plant is sometimes cultivated, and in some parts of the world is cooked and eaten as a vegetable. 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 Vale, NC., 8-23-03 (DETenaglia); also at Busch Wildlife Area, St. Charles County, MO, 8-30-2008, Weldon Spring Conservation Area, St. Charles County, MO, 8-16-2011, and along the Duckett-Busch greenway, St. Charles County, MO, 9-25-2017 (SRTurner).


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