Cyperus difformis L.
Synonyms - Cyperus complanatus, Cyperus protractus
Cyperus is from the Greek kypeiros or the Latin cuperos both meaning sedge or rush.
Other names:Smallflower Umbrella Plant
Variable Flat Sedge
Summary:A hairless, tufted annual, to 750 mm 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.
Blade - Grass like, parallel sided, limp and weak. Shorter than to slightly longer than stems, 100-800 mm long x 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 x 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 x 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 a 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.
Seeds:Pale or yellowish. 3 angled with projecting ridges and flat sides. Egg shaped to oval in outline. 0.6 mm long x 0.4 mm wide. Minutely granular surface.
Annual. Flowers January to July.
Flowering times:January to July in SA.
Summer and winter in NSW.
Seed Biology and Germination:Vegetative Propagules:
Population Dynamics and Dispersal:
Spread by seed.
Origin and History:Europe, Africa and Asia, tropical Asia.
Distribution:ACT, NSW, NT, QLD, SA, VIC, WA.
Courtesy Australia's Virtual Herbarium.
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.
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.
Management and Control:Thresholds:
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:Kyllinga weed (C. sesquiflorus) has a very short or no rhizome, and often 2 small spikes at the base of a larger one, which are whitish or pale green.
Kyllinga weed (C. sphaeroideus) has a yellowish seed head, usually less than 50 flowers and is an annual.
Nutgrass (C. rotundus) has underground tubers or 'nuts'.
Downs Nutgrass (C. bifax) has small tubers.
Yellow Nutgrass (C. esculentus) is similar until flowering when it produces a yellow green flower head.
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.
Ciba Geigy (1982) Grass Weeds 3. CIBA GEIGY Ltd, Basle, Switzerland. P15. Diagrams.
Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P159. Photo.
Gardner, G.A. and Bennetts, H.W. (1956). The toxic plants of Western Australia. (West Australian Newspapers Ltd, Perth). P13
Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).
Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #404.9.
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