Button grass

Dactyloctenium radulans (R.Br.) P.Beauv.

Synonyms - Eleusine radicans, Eleusine radulans, Eleusine aegyptiaca, Dactyloctenium aegyptium, Dactyloctenium aegyptiaca, Dactyloctenium australiense.

Family: Poaceae

Names:

Dactyloctenium is from the Greek daktylos meaning finger and ktenion meaning comb and refers to the seed heads being comb like in a fingered arrangement.

Other Names

Finger grass.

Summary:

A somewhat ephemeral, summer growing, semi erect, annual grass to 40 cm tall with spreading branches forming leafy tufts. It responds rapidly to summer rains.

Description:

Cotyledons:

One.

First leaves:

Leaves:

Base grass like, sides tapering, tip pointed.
Blade - 80 mm long x 2-6 mm wide at the base tapering to a point. Flat, rough to touch or smooth, sometimes with long hairs. Edges are often wrinkled or fringed with long (1.5-2 mm) tubercle based hairs. Folded in the bud.
Ligule - 0.5 mm long, membranous with a ciliate margin
Auricles - None.
Sheath - loose, almost keeled. Smooth or with a few tubercle based hairs

Stems:

Many to 400 mm long. Prostrate to ascending to erect. Slender, smooth and hairless. Often bent at the smooth nodes. Rarely branched. Terete or angular striate.

Flower head:

An umbel of 3-10 (usually 3-6) compact spikes in a finger like arrangement forming compact globular head at the ends of the stems.
The spikes are 5-13 mm long, ending in a sterile rachis point. They eventually spread then fall intact from the plant with the spikelets attached. The backbone (rachis) of the spike is angular and keeled on the back. The spikelets are regularly and closely overlapping.

Flowers:

Spikelets - 5 mm long. 2-5 flowered. Bristly or very shortly awned. Compressed, stalkless and crowded in 2 rows along one side of the rachis and almost at right angles to it. Rachis extends to form a firm point
Florets - Terminal floret barren. Rachilla disarticulating.
Glumes - One nerved, shorter than the floret. Broad and boat shaped. First is 1-2.5 mm long, persistent and elliptical. Second is 1.5-3 mm long with a sharp tip, deciduous and narrowly egg shaped. Both are rough to touch on the keel.
Palea - Shorter than the lemma, acute, complicate, the nerves ciliate. 2 keeled.
Lemma - 2.5-5 mm long, egg shaped, rough to touch on the keel. Broad, stiff, keeled, acuminate, curved outward along the keel, 3 nerved. Broad membranous margins
Stamens -
Anthers -

Fruit:

Seeds:

Small.

Roots:

Fibrous.

Key Characters:

Tufted annual.
Spikes 3-10, each 5-15 mm long.
Spikelets 5 mm long, crowded and touching those of adjacent spikes.

Biology:

Life cycle:

Annual or short lived perennial. Germinates after summer rains and grows quickly.

Physiology:

Salt tolerant. Drought tolerant.

Reproduction:

By seed.

Flowering times:

Flowers in response to rain.
January to June and October in WA.
January to July in SA.
Spring to Summer in NSW

Seed Biology and Germination:

Germinates quickly after rain.

Vegetative Propagules:

None.

Hybrids:

None.

Population Dynamics and Dispersal:

Grows rapidly after summer rains.

Origin and History:

Australian native plant.

Distribution:

ACT, NSW, QLD, NT, SA, VIC, WA.

Courtesy Australia's Virtual Herbarium.

Courtesy DEC Florabase.

Habitats:

Open areas, seasonal swamps, river banks.

Climate:

Very widespread and tolerates a large range of climates.

Soil:

Tolerates a wide range of soils, including slightly saline and swampy soils. More common on sandy and loamy soils.

Plant Associations:

Desert plants.

Significance:

Beneficial:

Important pasture grass in central Australia.

Detrimental:

Weed of summer fallows, roadsides and gardens. Occasionally toxic.

Toxicity:

Can be toxic to cattle in poor condition. Occasionally toxic to sheep especially when hungry stock are exposed to lush green growth.
The toxicity is caused by prussic (hydro cyanic) acid which can build up to toxic levels under some conditions which are usually related to the climate and soil and is more common during periods of rapid regrowth. Young succulent fast growing plants are more likely to be toxic. Prussic acid is lost during drying and hay or dry feed is rarely toxic.

Symptoms:

Spasms and respiratory failure, weak pulse, bright red membranes on the linings of the eyes, nose and mouth which then turn purple (cyanosis).
Salivation, frothing at the mouth, muscles twitches, staggering gait, dilation of pupils, pronounced bloat followed by coma and death. The heart may continue to beat for some time after breathing has stopped.

Treatment:

Remove animals from the infestation.

Legislation:

The Wildlife Conservation Act prohibits removal of native plants from the wild in their native range on government land.

Management and Control:

Grazing usually provides adequate control. In wet summers it can build up to large swards very quickly. Knockdown herbicides can be used if necessary.

Thresholds:

Variable. Usually controlled in fallows to conserve moisture.

Eradication strategies:

Prevent seed set.

Herbicide resistance:

None reported.

Biological Control:

None.

Related plants:

Dactyloctenium aegyptium has longer spikes at 15-40 mm and shorter spikelets at 2.5-3 mm.
Dactyloctenium australe or Durban grass or Sweet smother grass is a stoloniferous perennial used as a shade tolerant lawn introduced from South Africa.

Plants of similar appearance:

Grasses.
Windmill grass (Chloris truncata) has much longer spikes
Tall wheatgrass (Lophopyrum elongatum) has compact spikes but they are not in a finger like arrangement and the plant is much larger.
Cyperus sedges also have similar compact spikes but their leaves have no sheath or ligule.

References:

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). Diagram. Part 1, P187

Ciba Geigy (1981) Grass Weeds 2. CIBA GEIGY Ltd, Basle, Switzerland. P56. Diagrams.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). Photo. P79.

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

Gardner, C.A. (1951) The Flora of Western Australia. Vol 1. Part 1. Gramineae. P209-210. Diagram.

Gardner, G.A. and Bennetts, H.W. (1956). The toxic plants of Western Australia. (West Australian Newspapers Ltd, Perth). P12.

Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume . P528. Diagram.

Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P

Lamp, C.A., Forbes, S.J. and Cade, J.W. (2001). Grasses of Temperate Australia. Revised Edition. (Blooming Books, Melbourne). P. Diagram.

Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). #325.

Paczkowska, G. and Chapman, A. (2000). The Western Australia flora: a descriptive catalogue. (Wildflower Society of Western Australia (Inc), the Western Australian Herbarium, CALM and the Botanic Gardens & Parks Authority). P100.

Paterson, J.G. (1977). Grasses in South Western Australia. (Western Australian Department of Agriculture Bulletin 4007). P44.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.