A hairless, tufted annual, to 750mm high with globular clusters of seeds on short stalks above a long-leaf-plus-2-short-leaf combination at the top of a triangular stem.
Description:
Cotyledons:
One
Leaves:
Few, basal.
Blade - Grass like, parallel sided, limp and weak. Shorter than to slightly longer than stems, 100-800 mm long by 2-4 mm wide. Straw coloured to brown on the lower leaves. Hairless. May be reduced to loose basal sheaths.
Sheaths - red brown.
Stems:
Soft(easily compressed), green, smooth, erect, triangular, smooth, 100-750 mm tall by 2-4 mm wide with a thickened base. Single or tufted with many stems. Hairless.
Flower head:
Simple umbel with 3-11 spreading primary rays to 50 mm long, (rarely has secondary rays to 10 mm long) or reduced to a dense head. More than 40 spikelets arranged in a star shape in a dense, almost globular cluster. 6-15 mm wide, up to 11 short spreading straight flower branches to 50 mm long. 1-3 bracts underneath. Lowest bract is up to 250 mm long and longer than flower cluster and erect pushing the cluster to one side.
Flowers:
Spikelets - dark brown to red-black or occasionally pale green, sometimes turn mottled, 8-40 flowered, parallel sided, flattened. 2.5-8 mm long by 1-1.2 mm wide. Stalkless. Spikelet axis (rachilla) is persistent, wingless, straight with an internode length of 2 mm.
Florets - Bisexual ones present. 3 branched style that is not dilated at the base.
Glumes - like a narrow conical cap split on one side. 0.6-0.8 mm long and 0.5-0.7 mm wide. The middle section is pale and the sides have a red-brown to purple stain. Round tip, usually with 3 nerved green stripe down the middle and the sides red brown to purplish. Scarcely keeled. In opposite rows.
Perianth - absent.
Stamens -1-3, usually 1.
Anthers -
Fruit:
Nut.
Seeds:
Pale or yellowish. 3 angled with projecting ridges and flat sides. Egg shaped to oval in outline. 0.6 mm long by 0.4 mm wide. Minutely granular surface.
Roots:
Reddish, fibrous.
Key Characters:
Biology:
Life cycle:
Annual. Flowers January to July.
Physiology:
Reproduction:
By seed.
Flowering times:
January to July in SA.
Summer and winter in NSW.
Seed Biology and Germination:
Vegetative Propagules:
Hybrids:
Allelopathy:
Population Dynamics and Dispersal:
Spread by seed.
Origin and History:
Europe, Africa and Asia, tropical Asia.
Distribution:
ACT, NSW, NT, QLD, SA, VIC, WA.
Habitats:
Damp to very wet areas. Shallow water. Common in irrigation areas and rice fields.
Climate:
Temperate to tropical.
Soil:
Heavy clay soils.
Plant Associations:
River Red Gum, Black Box, Lignum.
Significance:
Beneficial:
Detrimental:
Serious weed of rice. Important weed of rice in the Murrumbidgee Irrigation Area.
Weed of irrigated crops and grassland.
Toxicity:
Possibly toxic. Suspected of causing sheep deaths. May contain HCN.
Rarely a problem in the field.
Legislation:
None.
Management and Control:
Thresholds:
Eradication strategies:
Herbicide resistance:
Biological Control:
Related plants:
There are 38 Cyperus species recognised as economic plants by CSIRO the most common are:
Boredrain Sedge (C. laevigatus)
Clubrush (C. hamulosus)
Dirty Dora (C. difformis)
Dense Flatsedge (C. congestus)
Downs Nutgrass (C. bifax)
Dwarf Sedge (C. pygmaeus)
Dwarf White Kyllingia (C. kyllingia)
Flat Sedge (C. sanguinolentus)
Giant Sedge (C. exaltatus)
Kyllinga weed (C. sesquiflorus, C. sphaeroideus)
Mullumbimby Couch (C. brevifolius)
Nalgoo (C. bulbosus)
Navua sedge (C. aromaticus)
Nutgrass (C. rotundus)
Rice Flatsedge (C. iria)
Scaly Sedge (C. tenuiflorus)
Slender Sedge (C. gracilis)
Sticky Sedge (C. fulvus)
Stiff-leaved Sedge (C. vaginatus)
Spiny Flatsedge (C. gymnocaulos)
Tiny Flatsedge (C. tenellus)
Umbrella grass (C. eragrostis)
Yelka (C. victoriensis)
Yellow Nutgrass (C. esculentus)
Plants of similar appearance:
References:
Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P23. Photo.
Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P262. Diagram.
Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P80.