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 750 mm long. Prostrate to ascending to erect. Slender, smooth and hairless. Often bent at the smooth nodes. Rarely branched. Terete or angular striate. A single plant can produce up to 45 tillers. Prostrate and erect tillers are formed. The prostrate tillers may form roots at the nodes and form up to 8 secondary tillers. Each tiller has 2-3 seed heads.

Flower head:

An umbel of 2-11 (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 and contain 5-11 seeds.
There are normally 2-3 seed heads on each tiller in contrast to most other grasses that have one..

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:

Entire spikes with spikeets attached are shed to disperse seed.

Seeds:

Small, brown, less than 1m long and look like small grains of sand. 5-11 seeds per spikelet. Approximately 8000 seeds per plant and 32,000 seeds/m2 may be produced.

Roots:

Fibrous. Prostrate tillers may form roots at the nodes.

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 forming up to 45 prostrate and erect tillers. It normally as a staggered germination so plants at various stages are present. The prostrate tillers may form roots at the nodes and form up to 8 secondary tillers. A single plant may spread to over 1.5 m in diameter by this process. 2-3 seed heads are produced on each tiller.

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.
Seeds have an after ripening period and a partial light requirement for germination.
Scarification inceased germination to 90%.
Aproximatel 90% of seed on the soil surface germinates in the fisrt year and less than 10% of buried seed germinates in the first year.
Little or no germination occurs in the field in winter and spring.

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.
Often builds up in minimum tillage cropping systems.

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. Depletes moisture for following crops. Source of food for plague locusts.

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.
Overgrazing of green or dry plants (especially in stockyards) can lead to nitrate-nitrite poisoning.

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 to prevent seed set.
Cultivation to bury seeds is effective.
Control with herbicides can be compromised by stressful conditions that often occur in summer when Button Grass is growing.
Glyphosate followed by paraquat or Spray.Seed®(paraquat+diquat) or paraquat + amitrole mixes provides good control.
Paraquat based products generally only provide initial burn down with regrowth a few weeks later.
Imazapic or pendimethalin can be used for residual control.
Stubble burning will reduce the seed bank and provide some control.

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

(Borger et al., 2017b)

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.

(Borger et al., 2017b)

(Hashem and Amjad, 2017)

Acknowledgments:

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