Windmill grass

Chloris truncata R. Br.

Family: - Poaceae


Chloris is from the Greek word chloros meaning bright green and refers to the leaf colour.

Truncata refers to the truncate or flat topped lemma in the flower.

Windmill grass refers to the shape of the seed head.

Other Names:

Umbrella grass

Star grass

Blow-away grass


Windmill Grass is an erect , short, tufted, hairless, annual to perennial grass with stems that turn upward with a windmill like seed head with 6-9 spokes with many tiny spikelets. The spikelets each have 2 or 3 florets and the outer segment of each floret (lemma) has a straight bristle (awn). It grows to 50 cm high and flowers at various times in various areas.





Emerging leaf rolled in the bud.

Blade - Bluish green, 50-140 mm long by 1-5 mm wide. Green, narrow, rough to touch, folded or flat, rarely hairy.

Ligule 0.5 mm long, thick. Densely hairy.

Auricles - None.

Sheaths - Flattened, folded, keeled, hairless, smooth, striped. Loosely wrapped around the stem, prominent midrib, membranous edges.


Erect or kneed at the base, 160-450 mm tall, flattened, smooth, 2-3 nodes, dense low crown. Normally tufted but can develop a close sward under grazing. Usually unbranched, but occasionally with short branched stems that root at the nodes (stolons).

Flower head:

5-10, slender, straight, spike like racemes, 40-190 mm long, held horizontally when in flower, like spokes of a windmill, rigid or slightly drooping. Hairy and bare at the base. Spreading. 2 crowded rows of seeds on the underside of each spoke.


Spikelets - Flattened, on 1 mm stalks. Almost black at maturity, in 2 rows, alternately and loosely overlapping on the underside of spread branches.

Florets - 2 or rarely 3 per spikelet, often black . Lower one bisexual. Upper one(s) empty.

Glumes - Membranous or thin and transparent, one veined. Tapered and may have a short point. Cusps. Rough on the keel. First (lower) one 1-2 mm long. Second (upper) one 2.5-4 mm long.

Palea - Same length as lower lemma. Obtuse tip. 2 keeled and hairy on the keels. Dark coloured, membranous. No palea on upper lemma.

Lemma - 2, both look like they have been cut off at the top (truncate). First (lower) fertile one, triangular, 3-4 mm long, looks like cartilage, inflated, rough to touch or smooth, 11-14.5 mm, slender awn that is rough to touch near the tip. hairy on the upper margins, or veins, hairless elsewhere, held close to lower lemma. Rounded on the back, black when mature. The tip has 2 small lobes or is rounded or cut-off.

Second (upper) one 1-4mm long, triangular, somewhat flattened but rounded on the back, hairless, inflated flat on top or with a notch, 5-14.5 mm long thread like awn that is rough to touch. On a slender internode of the rachilla. Tip level with the lower lemma. No palea.

Ovary - hairless. Style short, distinct. Stigma feathery.

Stamens - 3

Anthers -


Small, narrowly egg shaped to spindle shaped in outline, somewhat triangular, 1.5mm long. Translucent. Pointed tip.



Key Characters:

Callus short, obtuse or rarely acute, not exceeding 2mm and usually much less.

Spikelets with 1 or rarely 2 upper florets sterile or female.

Fertile lemma broad at the apex, very obtuse or truncate, divaricate at maturity, awned.

Awn conspicuous and much longer than the lemma

Adapted from C.A. Gardner.


Life cycle:

Perennial or annual. Germinates after spring and summer rains and plants continue to grow until drought or severe frost occurs.


Sensitive to frost.


By seed and stolons.

Flowering times:

Mainly summer and occasionally in autumn and spring in NSW.

November to June in SA.

March to July with odd ones in December in WA.

Seed Biology and Germination:

Vegetative Propagules:




Population Dynamics and Dispersal:

It sets large amounts of seed.

Origin and History:




The southern extent of this WA native species, found usually in the wheatbelt and goldfields, is uncertain. Its weedy nature on the south coast of WA may be indicative of it not being a native species in that area.




Often on flats around the edges of claypans.

Common on grey clays and red earths.

Occurs on most soil types.

Plant Associations:

Wide range.

Native pastures.



Palatable fodder when young but often becomes rank and unpalatable unless managed. Seed heads are unpalatable.

Use for stabilising clay soils to reduce erosion in waterways.


Weed of pastures, lawns and disturbed areas.


May contain toxic levels of HCN but field cases of poisoning are rare.

May causes photo sensitisation after consumption of lush growth in hot weather.



Remove stock from infestation.

Don't graze lush growth in hot weather.



Management and Control:


Eradication strategies:

Continual grazing often provides reasonable control.

This plant spreads rapidly which makes eradication difficult unless it is practiced on a wide scale basis. In areas threatened by invasion, spraying the road shoulders with glyphosate and spot spraying satellite infestations will reduce the rate of spread.

Use 80 mL of glyphosate(450g/L) in 10 L water in early summer when the plants are actively growing or 4 L/ha on larger areas. 2 kg/ha of simazine(900g/kg) can be used as a pre-emergence treatment in spring.

Herbicide resistance:

Biological Control:

Related plants:

Comb Chloris (C. pectinata)

Feathertop Rhodes grass (C. virgata)

Purpletop Chloris (C. barbata, C. inflata)

Rhodes Grass (C. gayana)

Slender Chloris (C. divaricata)

Tall Chloris (C. ventricosa)

(C. acicularis) Enteropogon acicularis

Dysphania pumilio

(C. scariosa) Oxychloris scariosa

Plants of similar appearance:


Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P42. Photo.

Black, J.M. (1978). Flora of South Australia. (Government Printer, Adelaide, South Australia). P205. Diagram.

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P59-60. Diagram.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P76. Photo.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P307-308.

Gardner, C.A. (1952). Flora of Western Australia. Volume 1, Part 1. P219-221. Diagram.

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). #300.9.

Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P948.

Paterson, J.G. (1977). Grasses in South Western Australia. (Western Australian Department of Agriculture Bulletin 4007). P37. Diagrams.


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