Description:

• Perennial or annual herbs; roots thin or swollen; stems branched, erect to spreading or rarely succulent; when perennial usually dying down in winter to a persistent knobbly crown with long hard roots (chamaephytes); sometimes with underground stolons bearing cleistogamous flowers often developing capsules and seeds (C. benghalensis L. and C. forskaolii Vahl)
• Leaves distichous or spirally arranged, blade sessile or petiolate, base often oblique, sheathing base usually ciliate at mouth
• Inflorescence terminal, composed of 1 or 2, 1-6-flowered cymes, cymes enclosed in terminal or leaf-opposed, obliquely funnel- to boat-shaped spathe with either free margins or margins of proximal end fused, straight; spathe mucilaginous or dry inside when flowering; upper cyme 1(2 or 3)-flowered, usually male (with or without a pistillode) exserted on a long peduncle, in some species absent or represented by a vestigial peduncle, often enclosed within spathe; lower cyme included in spathe, borne on a short peduncle
• Flowers 2-6, all bisexual or some male, irregular, just exserted in turn at anthesis; pedicels recurved inside spathe when in fruit; flowers open in morning for a few hours, soon deliquescent
• Sepals sepaline, free or lower 2 fused
• Petals free; upper 2 large, flat, long-clawed, blue, white or yellow or related colours; lower one reduced, often colourless or different in colour to others
• Stamens 3, anterior one (lower) fertile, central one usually with a larger anther with a broad connective; (2)3 posterior (upper) staminodal, reduced; antherodes cruciform or variously deformed; filaments glabrous
• Ovary 2- or 3-locular, 2 ventral locules, and 1 dorsal locule sometimes reduced to absent; ventral locules 1- or 2-ovulate, dorsal locule 1-ovulate or sterile
• Fruit a loculicidal capsule; in some species dorsal locule indehiscent, smooth or striate-muricate with capsule wall fused to seed and laterally attached to part of walls of ventral locules, forming a shallow cup
• Seeds (2-)5, globose, ellipsoid or cylindric-truncate; testa various; hilum linear; embryotega lateral
• x = 10, 11 (8, 9, 12, 13, 14)

Nomenclature:

• Commelina L.
  • Linnaeus: 40 (1753)
  • Clarke: 8 (1897)
  • Clarke: 33 (1901)
  • Morton: 507 (1956)
  • Schreiber: 2 (1967)
  • Obermeyer & Faden: 24 (1985)

Distribution & Notes:

• Global: Species ± 170, warmer countries of the world
• Southern Africa: Species 16, widespread.