Cyperus rotundus - Purple nutsedge
Herbaceous, up to 60 cm tall with slender, more or less horizontally spreading rhizomes coated with dark-coloured fibres; rhizomes bearing ovoid, blackish, fibrous tubers.
Erect, thickened at the base, glabrous, smooth, three-angled.
Leaves: Grasslike, up to 50 c long and 8 mm wide, expanded, glabrous, smooth and shiny.
A compound or almost simple umbel, bracteate; bracts 3-4, similar to leaves, as long as or slightly longer than the umbel.
Up to 2 cm long, 10-24 flowered, compressed, red or reddish-brown; glumes angular, acute, prominently nerved, light green or yellow on the keels.
Widely distributed throughout South Africa.
This species is characterized by a thickening at the base of the stem. It is more difficult to control as it resists most selective herbicides. It produce massive numbers of tubers that can germinate from as deep as 30 cm.
HOROWITZ, M. & FRIEDMAN, J., 1971. Biological activity of subterranean residues of Cynodon dactylon L., Sorghum halapense L. and Cyperus rotundus L. Weed Research. 11,88-93.
RICE, E.L., 1995. Allelopathy in forestry. In: E.L. Rice (ed.). Biological control of weeds and plant diseases: Advances in applied allelopathy. University of Oklahoma Press. Norman. 317-378.