Commelina virginica L.

Virginia Dayflower

Commelina virginica plant2

Family - Commelinaceae

Habit - Perennial forb with rhizomes and thickened, fibrous roots.

Stems - Erect to ascending, to 1.2 m, sometimes rooting at the lower nodes.

Commelina virginica stemStem and leaf sheath.

Leaves - Alternate, simple, entire. Blades 8-20 cm long, lanceolate, sometimes somewhat scabrous. Leaf sheaths mostly 1-3 cm long, ciliate with reddish brown hairs, the tips lacking auricles of tissue.

Commelina virginica leaves

Commelina virginica sheathSheath.

Commelina virginica leaf1Leaf adaxial.

Commelina virginica leaf2Leaf abaxial.

Inflorescence - Mostly clustered near the tips of the stems, sessile or short-stalked, the folded spathelike bracts 20-32 mm long, the margins fused in the lower third, the lower edge (midrib of the bract) curved and noticeably arched or less commonly nearly straight.

Commelina virginica inflorescenceInflorescence.

Commelina virginica spathe2Spathe.

Flowers - Sepals 3-5 mm long. Petals 3, somewhat unequal (the lower 1 similar in appearance to the expanded, bladelike portions of the upper 2), the upper 2 petals 11-17 mm long, clawed, blue, the lower petal 9-13 mm long, blue. All 3 staminodes with well-developed false anthers, these 4-6-lobed, yellow, lacking a reddish brown spot in the middle. Stamens 3, 1 of which is incurved and has a longer anther than the other 2, the filaments glabrous.

Commelina virginica flowers2Flowers.

Fruits - Capsules 4-6 mm long, 2-3-locular and 4-5-seeded. Seeds 3-6 mm long, the surface smooth to slightly granular.

Flowering - July - September.

Habitat - Bottomland forests, streambanks, swamp margins, sloughs, ditches.

Origin - Native to U.S.

Lookalikes - Other species of Commelina; more broadly, Tradescantia.

Other info. - This is the largest species of dayflower found in Missouri. It occurs in the southern half of the state, as well as across the southeastern quadrant of the continental U.S. The plant is easily recognized by its tall stature and flowers having three blue petals and glabrous stamens. The spiderworts (genus Tradescantia) also have blue flowers with three petals, but those flowers have 6 stamens with dense blue hairs on the filaments. The spathelike bracts found in the dayflowers are also absent in Tradescantia. The tawny hairs on the leaf sheaths of Commelina virginica are also unique. The plant is the only rhizomatous species of dayflower in Missouri, though digging up the plant for purposes of identification is frowned upon.

C. virginica is often attacked by an insect which eats long, narrow slots in the leaves. The plants seem able to withstand this predation without excessive impact on their health.

Photographs taken in Brown Summit, NC., 7-31-02 (DETenaglia); also at Otter Slough Conservation Area, Stoddard County, MO, 7-31-2015 and 8-13-2015 (SRTurner).