Asiatic Dayflower (Commelina communis): Invasive Beauty with True Blue Flowers

Overview

Asiatic dayflower (Commelina communis) is an annual herb native to East Asia, now naturalized across much of North America. Its striking, true-blue flowers—rare in the plant world—last only a single day, but are produced continuously from summer to frost. Despite its beauty, it is considered an invasive weed in many regions.

Botanical Description

Prostrate to ascending stems 30–90 cm long, rooting at nodes. Leaves are lanceolate, 3–10 cm long, sheathing the stem. Flowers have two large, vivid blue petals and one small, inconspicuous white petal, 1–1.5 cm wide. They open in the morning and wither by afternoon. Fruit is a two-valved capsule with 2–5 seeds.

Taxonomy

Family:	Commelinaceae (ko-mel-ih-NAY-see-ee)
Genus:	Commelina (kom-uh-LIN-uh)
Species:	communis (KOM-yoo-nis)

Habitat and Spread

Thrives in moist, disturbed soils: gardens, fields, roadsides, stream banks. Spreads by seed and vegetatively via rooting nodes. Seeds remain viable in soil for years. Listed as invasive in several U.S. states; outcompetes native vegetation in wetlands and floodplains.

Management

Hand-pull before seed set; remove all rooting nodes. Mulch heavily to suppress germination. Pre-emergent herbicides in spring. No biological controls established. Do not cultivate or share this plant.

Notes

The genus name honors Dutch botanists Jan and Caspar Commelin. The two blue petals represent the two brothers; the tiny white petal, their less-famous sibling. Young shoots are edible (cooked) in some Asian cuisines.