Asiatic dayflower (Commelina communis)

Common Names: Common dayflower, dayflower

Description:

Asiatic dayflower (Commelina communis) is a low, sprawling annual plant from eastern Asia, named for flowers that open for only a single morning [1]. It was introduced to North America and now grows as a weed of gardens, crops, and moist, shady, disturbed ground across the eastern United States [1]. MISIN tracks it as a non-native species to map where it occurs; it is mainly a garden and field weed rather than a plant that overruns healthy natural areas [1].

Habit:

Asiatic dayflower is a summer annual with smooth, round, hairless stems that either stand up to about 3 feet or, more often, sprawl across the ground like a vine and root where the joints touch moist soil [1]. Its leaves are smooth and hairless, broadly lance- to egg-shaped, up to about 5 inches long, with a thin sheath that wraps the stem at the base of each leaf [1]. The flower is the giveaway: two large, showy blue petals stick up like a pair of ears, with a third, much smaller white petal below, and the whole flower sits cupped in a folded, leaf-like bract [1]. Each flower lasts only one morning, but the plant blooms from mid-summer into early fall ? the easiest time to spot and identify it [1].

At-a-glance cues:

1. Flowers with two large blue petals (like ears) and one small white petal below, cupped in a folded bract [1]
2. Smooth, round, hairless stems that sprawl and root at the joints [1]
3. Smooth, hairless leaves up to ~5 inches long, each with a sheath wrapping the stem [1]
4. Each flower open for only a single morning; blooms mid-summer to early fall [1]

Leaves:

1. Arranged alternately along the stem, with parallel veins [1]
2. Broadly lance-shaped to egg-shaped, up to about 5 inches long and 2 inches wide [1]
3. Smooth and hairless [1]
4. Base forms a thin membranous sheath, about 1 inch long, that wraps around the stem [1]

Stems:

1. Herbaceous summer annual; stems round, smooth, and hairless [1]
2. Either erect to about 3 feet or sprawling up to about 10 feet along the ground like a vine [1]
3. Roots at the joints (nodes) where sprawling stems touch moist soil [1]

Flowers:

1. Two large, showy blue petals above and a third much smaller white petal below, with yellow stamens [1]
2. About ? to 1 inch across, cupped in a folded, leaf-like bract (spathe) [1]
3. Each flower lasts only a single morning; the plant blooms from mid-summer into early fall [1]
4. Each flower has both male and female parts (perfect) [1]

Fruit and seeds:

1. Fruit is a small two-chambered seed capsule, with two seeds in each chamber [1]
2. Seeds are dark brown to black, with a bumpy, rough (pitted) surface [1]
3. The plant spreads by these seeds and by rooting from stem joints [1]

Habitat:

Asiatic dayflower grows in moist, fertile ground in full sun to light shade ? gardens, crop fields, yards, roadsides, stream banks, and shady, disturbed places [1]. It does best on rich loamy or slightly sandy soils that stay moist [1]. It is native to eastern Asia and has been introduced to eastern North America and to Europe, where it has naturalized as a weed [1][2]. It favors already-disturbed, moist ground rather than intact natural plant communities [1].

Reproduction:

Asiatic dayflower spreads two ways [1]. It sets seed in small capsules, and those seeds move in soil, in dumped garden waste, and on tools and equipment [1]. It also creeps: its sprawling stems root wherever a joint touches moist ground, and broken stem pieces can take root and start new plants, so it can spread from a neighbor's yard or from a discarded clipping [1]. It is a summer annual ? plants sprout in spring, flower and set seed through summer and fall, then die, with the seeds carrying the population to the next year [1].

Because it comes back from both seed and rooted stem pieces, the key to control is removing whole plants ? including the rooted joints ? before the flowers set seed in summer [1].

Impact and Damage:

Asiatic dayflower is not poisonous to people or pets [1]. Its trouble is as a weed. The sprawling stems root as they go and form spreading mats that can smother low garden plantings and compete with vegetables, ornamentals, and field crops, and the plant is known for being persistent and hard to clear once established [1]. In natural areas its effect is more limited and local: it moves into moist, shady, disturbed spots ? stream banks, trail edges, and woodland borders ? rather than crowding out healthy stands of native plants [1]. Its main importance there is as a widespread non-native weed and a sign of disturbed, damp ground [1][2].

Similar species:

Asiatic dayflower is mixed up with other members of the spiderwort family. The two-blue-petals-plus-one-small-white-petal flower and the smooth, hairless, sprawling stems are the best clues.

Slender dayflower (Commelina erecta) is a native dayflower with similar blue flowers. But its folded flower bract is joined (fused) along the lower edge, its leaves are narrower, and its bracts, leaves, and stems are covered in stiff hairs, whereas Asiatic dayflower is mostly smooth and hairless [1].

Benghal dayflower (Commelina benghalensis) is another dayflower and a U.S. Federal Noxious Weed. It has rounded leaf tips and reddish hairs along the leaf sheath, and it produces hidden underground flowers and seeds in addition to the showy blue ones ? features Asiatic dayflower lacks [1].

Spiderworts (Tradescantia species, such as Virginia spiderwort) are related plants with similar grass-like leaves and blue-purple flowers. But their flowers have three equal petals rather than the two-large-plus-one-small arrangement of the dayflowers [1].

Monitoring and rapid response:

Signs to watch for:

1. Flowers with two blue "ears" and one small white petal, cupped in a folded bract, in mid-summer to early fall [1]
2. Smooth, round, hairless stems sprawling across the ground and rooting at the joints [1]
3. Smooth, hairless leaves with a sheath wrapping the stem [1]
4. Spreading mats in moist, shady, disturbed ground ? gardens, field edges, stream banks [1]

What you can do:

1. Pull or hoe out plants ? the roots are shallow and lift easily, especially when young and the soil is moist [1]
2. Be sure to remove the rooted stem joints and any broken pieces, since they can re-root [1]
3. Remove plants before the flowers set seed in summer, and bag seeding plants and rooted fragments rather than composting them [1]
4. Keep bare, moist ground mulched or planted so seedlings have nowhere to establish, and clean soil off tools between areas [1]
5. Natural area crews can pull or hoe plants from moist, disturbed spots before they set seed, focus on stopping seed production, and limit soil disturbance that opens ground for it [1]

When to call a professional:

1. Large, persistent infestations in crops or landscapes where hand removal cannot keep up [1]
2. Repeated re-infestation from a built-up seed bank or rooted mats [1]
3. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. North Carolina State Extension Gardener Plant Toolbox. Commelina communis (Asiatic Dayflower). plants.ces.ncsu.edu
2. Native Plant Trust, Go Botany. Commelina communis (Asiatic dayflower). gobotany.nativeplanttrust.org
3. USDA NRCS PLANTS Database. Commelina communis L. (COCO3). plants.usda.gov

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