Common Australian Garden Weeds

Cyperus rotundus

Scientific name: Cyperus rotundus L.


Young nutgrass plant (Cyperus rotundus).


Nutgrass in flower.


Nutgrass in flower again.


Close-up of nutgrass in flower with clusters of reddish flower spikelets.

Common name: Nutgrass

Family: Cyperaceae

Origin:

Native of India, widespread through warmer parts of the world.

Habit:

Perennial grass-like herb up to 60 cm high with underground tubers.

Habitat:

Found in most parts of the country except the coldest and driest areas. It is very difficult to eradicate because the tubers allow survival through times of intense heat, flooding and droughts. It is also a pest in suburban lawns and gardens.

General description:

Stems and leaves

Underground runners form dark, egg-shaped tubers with a brown fibrous covering. Stems are erect, slender, 3-angled and 15-40 cm long, 1-2 mm wide. Leaves can be shorter or longer than the inflorescences, they are 2-6 mm in width.

Flowers and fruit
The inflorescence consists of a stalk with 2-4 green bracts underneath a cluster of 3-8 stems (varying in length, up to 10 cm long) each carrying several flattish reddish-brown spikelets towards its end. Seeds usually do not mature, so that tubers are the primary means of reproduction.

Distinguishing characteristics:

Perennial grass-like plant with clusters of reddish-brown spikelets differentiating C. rotundus (nutgrass) from a similar species C. polystachyos (bunchy sedge) which has an irregular bunched up inflorescence.

Noxious status:

Noxious in South Australia.

Sources:

Kleinschmidt, H.E., Holland, A. and Simpson, P. (1996). Suburban Weeds. 3rd Edition. Department of Primary Industries, Brisbane.

Stanley, T.E. and Ross, E.M. (1983-1989). Flora of South-eastern Queensland. Volume 3. Department of Primary Industries, Brisbane.

Friend, E. (1983). Queensland Weed Seeds. Department of Primary Industries, Brisbane.

Anonymous. (1994). Queensland Vacsular Plants: Names and Distribution. Queensland Herbarium, Brisbane.