Commelina

Commelina L.

Commelina is a rather large genus of ca. 170 species. It is nearly cosmopolitan (except cold regions) but chiefly occurs in the tropics. None is native in Belgium. Some species are economically important, either as ornamentals or as noxious weeds of agricultural fields.

Species of Commelina are often very reluctant to flower in western Europe. In the absence of flowers identification is impossible.

1. Spathe margins free to base. Lower petal blue or white. Capsule 2- or 3-locular. Plant annual or perennial === 2

1. Spathe margins connate basally. Lower petal blue. Capsule always 3-locular. Plant always perennial === 4. Commelina obliqua

2. Plant usually erect, tall. Roots tuberous. Leaf sheaths and spathe distinctly hairy. Flowers showy, ca. 20 mm across, petals concolourous (all blue, exceptionally all white), all equally large === 1. C. coelestis

2. Plant prostrate, rooting at the nodes. Roots never tuberous. Leaf sheaths and spathe usually glabrous. Flowers smaller, petals concolorous or not, the lower petal always distinctly smaller === 3

3. Lower petal blue. Capsule 3-locular. Plant often slender === 3. C. diffusa

3. Lower petal white. Capsule 2-locular. Plant often more robust === 2. C. communis


Literature:

Brashier C.K. (1966) A revision of Commelina (Plum.) L. in the U.S.A. Bull. Torrey Bot. Club 93: 1-19.

Calderon de Rzedowski G. & Rzedowski J. (1988) Nota sobre el género Commelina (Commelinaceae) en el Valle de México con cambios en la nomenclatura de algunas de sus especies. Madroño 35: 16-22.

Clement E.J. & Foster M.C. (1994) Alien plants of the British Isles. BSBI, London: XVIII + 590 p.

Druet J. & Duvigneaud J. (1951) Note sur quelques phanérogames adventices. Lejeunia 15: 59-62.

Faden R.B. (2000) Commelinaceae. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 22. Oxford University Press, New York-Oxford: 170-197.

Forestier C. (1986) Note sur Commelina communis L. (Commelinales Commelinaceae). Bull. mens. Soc. Linn. Lyon, Suppl. 55(8): 1-3.

Hunt D.R. (1984a) Commelina. In: Walters S.M. & al. (eds.), The European Garden Flora, vol. 2. Cambridge University Press, Cambridge: 26.

Hunt D.R. (1984b) Tradescantia. In: Walters S.M. & al. (eds.), The European Garden Flora, vol. 2. Cambridge University Press, Cambridge: 30-31.

Hunt D.R. (1994) Commelina. In: Davidse G., Sousa M.S. & Chater A.O. (eds.), Flora Mesoamericana, vol. 6 Alismataceae a Cyperaceae. Universidad Nacional Autonoma de México, Missouri Botanical Garden & The National History Museum: 171-173.

Jäger E.J., Ebel F., Hanelt P. & Müller G. (eds.) (2008) Rothmaler Band 5. Exkursionsflora von Deutschland. Krautige Zier- und Nutzpflanzen. Springer Verlag, Berlin: 880 p.

Ogwal E.N.K. (1990) A taxonomic revision of the genus Commelina in Uganda. Mitt. Inst. Allg. Bot. Hamburg 23: 573-592.

Taxonomic name: 
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith