Commelina erecta aka Blue Commelina

Commelina erecta has two common names: slender day-flower and whitemouth dayflower. It is part of the Commelinaceae family. Its native range spans the Americas, tropical and southern Africa, and the Arabian Peninsula. Records in the Americas reach from the United States south to Peru. Kew links it to tropical climates with a dry season. Other sources place it in both tropical and temperate regions.

This soft-stemmed plant lives for more than two years. It has thin stems and fleshy roots with fine fibres. Its stems may stand upright or lie along the ground. Garden sources give heights of about 1.6–2.3 feet [0.5–0.7 metres]. The wider range in botany accounts reaches 1.3–3.9 feet [0.4–1.2 metres]. PFAF says its form looks like grass. The supplied species accounts say little about leaf shape. They give no clear account of its fruit. PFAF lists bloom times from July to September. Seeds ripen from August to October. Each flower has both male and female organs.

Wild plants grow in woods, clearings, and on rocky slopes. They grow in sandy and loamy ground. Some records also place them in wet thickets and forests. In gardens, use sandy soil or a light loam. The plant suits soil that drains well. Leaf mould can enrich loam. It accepts full sun or light woodland shade. Soil may be dry or moist. It tolerates slightly acid soil and neutral soil. Slightly alkaline soil suits it too. PFAF lists USDA zones 4–10. Its separate UK zone number does not establish an RHS hardiness rating.

Gardeners grow this long-lived plant for its looks. It suits beds, woodland edges, and gardens with light shade. It can also become a weed in cultivated ground. The evidence does not show how far it spreads. Grow new plants from seed, cuttings, or split clumps. PFAF suggests sowing seed under glass in March. Seeds take about four to five weeks to sprout at 20°C. Move young plants outdoors after the last expected frost. Split plants in early spring. Keep a growing bud on each piece.

Treat reports of food use with care. Useful Tropical Plants records people gathering roots from the wild. PFAF says sound proof of edible use is still lacking. It warns against using this species as food. Edible plants related to it do not prove its safety. The tropical source lists no known hazards. That does not mean it is safe for people or pets. PFAF lists no known uses in medicine.