Plants annual or perennial herbs with thin or tuberous roots. Leaves 2-ranked or spirally arranged,; blades sessile or petiolate, bases usually oblique but sometimes symmetric. Inflorescences terminal and leaf-opposed, composed of 1-2 cymes enclosed in spathers, lower cymes usually with several flowers, upper cyme sometimes lacking, vestigial, or producing 1-several, usually staminate but sometimes bisexual flowers; spathes with free margins or lower portions fused, often fillen with a mucilaginous liquid. Flowers bisexual and staminate, bilaterally symmetric; sepals green clearly distinct from the petals, free or the anterior 2 connate; petals free, the posterior 2 large and clawed, usually blue but sometimes lavender, yellow, peachm apricot, or white, anterior petal usually much smaller, sometimes different in colour; stamens 3, one different in form and size from the others, (2-)3 staminodes also present; filaments glabrous; ovaries 2-3-celled, dorsal cell with 1 ovule, or obsolete, other cells with 1-2 ovules. Capsules usually 2-3-celled, occasionaly 1-celled, with 1-5 seeds; seeds with linear hila.
Commelina includes about 170 species. They grow in tropical regions around the world but are most diverse in Africa.
