nutgrass

Cyperus rotundus
Nutgrass
Cyperus rotundus sprouting
Nutgrass
Nutgrass seed detail
Nutgrass infestation
Nutgrass seeds
Nutgrass roots
Nutgrass infestation
Nutgrass
Grass
Basal
Simple
Green
Green

A long-lived grass-like plant usually growing 20-50 cm tall. It produces a network of creeping underground stems with small tubers (10-25 mm long). Its upright flowering stems are smooth and three-angled in cross-section its very narrow leaves (7.5-20 cm long and 2-6 mm wide) are borne in a tuft at the base of the stems. Its seed-heads have 3-8 branches of varying in length (up to 10 cm long) and are subtended by two to four green leafy bracts. These branches bear several elongated reddish-brown or purplish-brown flower spikelets (10-25 mm long and 2-2.5 mm wide).

Common names 
Also known as: Coco grass, Ground almond, Java grass, Red nutgrass,
Family 
Cyperaceae
Deciduous 
No
Flowering time 
Summer-Autumn
Native/Exotic 
Exotic
Origin 
This species is thought to be native to parts of Asia and Africa, but its exact origin is obscure. It is found throughout most regions of the world (i.e. cosmopolitan).
Notifiable 
No
Council declaration 
SIL – Special Investigation List
Known distribution 

Widely naturalised and common in south-eastern Queensland. Widely naturalised in many other parts of Australia (i.e. eastern New South Wales, the ACT, Victoria, other part of Queensland, some parts of South Australia and Western Australia, and the northern parts of the Northern Territory). Also naturalised in on Lord Howe Island, Norfolk Island and Christmas Island.

Habitat 

A very troublesome weed of crops, orchards, vineyards, fallows, lawns, footpaths, gardens, parks, pastures, waste areas and disturbed sites.

Habit 

A long-lived (i.e. perennial) grass-like plant usually growing 20-50 cm tall, but occasionally reaching up to 60 cm in height. It produces creeping underground stems (i.e. rhizomes) with small tubers.

Impact and control methods 

A very troublesome weed of crops, orchards, vineyards, fallows, lawns, footpaths, gardens, parks, pastures, waste areas and disturbed sites.

Stem and leaves 

This weed has creeping underground stems (i.e. rhizomes) on which form dark coloured egg-shaped (i.e. ovoid) or oval (i.e. ellipsoid) tubers (10-25 mm long) with a brown fibrous covering. These tubers are white on the inside when young and become reddish brown as they mature. The flowering stems are upright (i.e. erect), slender (1-2 mm thick), rigid, smooth and three-angled in cross-section (i.e. trigonous). The very narrow (i.e. linear) leaves are borne in a tuft at the base of the stem. These leaves (7.5-20 cm long and 2-6 mm wide) can be shorter or longer than the stems. They have entire margins and pointed tips (i.e. acute apices). Both the leaves and stems are hairless (i.e. glabrous) and somewhat glossy in appearance.

Flowers and fruits 

The seed-head (i.e. inflorescence) is subtended by two to four green leafy bracts and has 3-8 branches of varying in length (up to 10 cm long). Each of these branches carries an irregularly-shaped cluster of several flattened reddish-brown or purplish-brown coloured flower spikelets towards its end. These elongated flower spikelets (10-25 mm long and 2-2.5 mm wide) are loosely arranged and have 10-40 tiny flowers (i.e. florets). Flowering occurs mostly during summer and autumn. The 'seeds' (i.e. nuts or achenes) usually do not mature. When produced, these 'seeds' (about 1 mm long) are somewhat egg-shaped (i.e. ovoid), but three-angled in cross-section (i.e. trigonous). They have a slight projection (i.e. beak) at the tip and are variable in colour (i.e. black, brown, grey or olive green).

Reproduction and dispersal 

This species reproduces vegetatively via its creeping underground stems (i.e. rhizomes) anf tubers.The rhizomes spread laterally and can eventually form large colonies. The tubers are also dispersed during cultivation and in contaminated soil.

Similar species 

The reddish-purple colour of the flower spikelets is the easiest way of differentiating nutgrass (Cyperus rotundus) from the similar tuber-producing species such as yellow nutgrass (Cyperus esculentus) and downs nutgrass (Cyperus bifax).