Paspalum

Paspalum dilatatum Poiret

Family: Poaceae.

Names:

Paspalum is from the Greek paspalos meaning millet.
Dilatatum
Paspalum

Other names:

Caterpillar Grass
Dallis Grass
Golden Crown Grass.
Leichardt Grass
Water Couch
Water Grass
Water Paspalum

Summary:

A tufted, rhizomatous, perennial, summer growing grass with leafy shoots coming from a central crown. Purplish-green spikelets are borne on one side of the 2-10, finger-like seed branches.

Description:

Cotyledons:

One

Leaves:

Dull to dark green. Emerging leaf rolled in the bud.
Blade - Flat, slightly keeled or angled along midrib, dark green often with a purplish tinge on the upper side, smooth, shining, soft, spreading or bending upwards. Bending upward or spreading. Parallel sided. 60-600 mm long x 3-15 mm wide. Wavy, roughened edges. Slender pointed tips. Mid vein prominent. A few hairs around the mouth otherwise hairless.
Ligule - Membranous, 2-4 mm long, flat on top to egg shaped.
Auricles - None.
Sheath - Tubular, flattened, loose, often hairy on the lower leaves.

Stems:

Erect, green and often tinged with purple, smooth, flattened, shortly rhizomatous, 400-1750 mm tall and tufted but spread into a solid leafy crown or sward when mown or grazed. Often kneed at the base, spreading or bending upwards and arching near the top. Hairless. A few branches from the lower nodes. Nodes conspicuous, often purple and rarely hairy. Doesn't root at the nodes. Mature plants usually have many stems arising from the crown.

Flower head:

Erect or drooping panicle, 70-250 mm long with 2-11 upward bending, spreading or drooping 1 sided, stalkless (sessile), racemes (seed branches), almost at right angle to the main axis. Rachis (raceme axis) narrowly winged, 1-1.2 mm wide, rough edges and long hairs where racemes arise. Each raceme 25-110 mm long x 2-4 mm wide, purple green, dense, angular, flattened holding 3-4 rows of paired spikelets on the underside. Racemes single or random on each side of the slender flattened, usually drooping panicle at the top of the stem.

Flowers:

Spikelets - Paired in 3-4 rows, overlapping, green or purple, oval to egg shaped with a pointed tip, flattened on the back, 2.8-4 mm long x 2-2.5 mm wide, pointed tip. Hairy. 2 flowered. In each pair of spikelets one has a short stalk and one has almost no stalk.
Florets - Lower one sterile.
Glumes - No lower one. Upper one slightly longer than the lower lemma and the same length as the spikelet, 2.8-4 mm long, 3-9 nerves near the edges and often hard to see, sparsely hairy to hairy with a fringe of fine long hairs, against the raceme. Side ribs often hard to see.
Palea - Circular. Hard.
Lemma - Lower one sometimes fringed with long hairs, same length as the spikelet, 2.8-4 mm long, 3-9 nerved. Upper one, fertile, broadly oval, hard, thin and brittle, shiny, minutely striped, edges incurved over palea.
Stamens -
Anthers - Purple, oblong, stick out of the spikelet.

Fruit:

Hard, shiny. 2-3 mm long flattened.

Seeds:

Enclosed in fruit. 2-3 mm long. There are about 50 seeds per raceme or up to 500 seeds per flowering stem. Seed adheres to material and fur.

Roots:

Fibrous roots and short creeping rhizomes crowded around the crown of the plant.

Key Characters:

Panicle usually with 2-11, one sided, sessile racemes. Spikelets crowded in 3-4 rows on the underside of flattened-angular rachis. Spikelets in pairs, occasionally 3 together. Margins of spikelet villous or long-ciliate. Upper glume slightly longer than the lower lemma.

Biology:

Life cycle:

Perennial. Summer growing. Dormant in winter. Flowers October - April.
Seeds germinate in moist warm months and seedling growth is slow, often taking 2-3 years to reach their first flowering.

Physiology:

Drought tolerant.
Waterlogging tolerant. It can survive submersion for several months.
Frost sensitive.

Reproduction:

By seed and rhizomes.

Flowering times:

Late spring to autumn in western NSW.
December to April in SA.
October to April in WA.
Spring and summer in WA.
December to July in SE Australia.

Seed Biology and Germination:

Mature plants can produce more than 250,000 seeds. A fungus often destroys many seeds.

Vegetative Propagules:

Rhizomes.

Hybrids:

Allelopathy:

Population Dynamics and Dispersal:

Spread by intentional planting, seed moving in water and seed adhering to stock and clothing.
On the edges of the stand it spreads around 1 m per year by the seeds falling from the tall, arching flowering stems.
Rhizomes moved in soil will re sprout.

Origin and History:

South America. Brazil to Argentina.

Distribution:

ACT, NSW, NT, QLD, SA, TAS, VIC, WA.
New Zealand.

Courtesy Australia's Virtual Herbarium.

Habitats:

Moist areas.

Climate:

Temperate in moderate to high rainfall (>500 mm) regions.

Soil:

More abundant on alluvial soils near streams.
Claypans.

Plant Associations:

Significance:

Beneficial:

Grazing tolerant fodder plant producing a good quantity of high quality, palatable forage if grazed to prevent it becoming rank.
Used in irrigated pastures. Frost sensitive but recovers quickly from rootstock.

Detrimental:

Weed of crops, watercourses, citrus, orchards, vineyards, lawns, vegetables, gardens, roadsides, rotation crops, grass lands, irrigation channels, drainage lines, streams, swamps, claypans, riparian and disturbed areas.
Seeds block irrigation equipment.
A major world wide weed listed as one of "The World's Worst Weeds" of crops.
The dense growth habit smothers most plants and prevents recruitment of overstorey species.

Toxicity:

Paspalum staggers is caused by a fungal ergot (Claviceps paspali) produced in the seed. It appears as a dark sticky exudate initially then turns into rounded bodies (sclerotia) about 3 mm long, yellowish-grey, dry and firm. The grass is toxic when the sclerotia are present from February to April.
Cattle are most commonly affected with fewer reports of problems with sheep and horses.
Occasionally it may cause illness in children who chew the seed heads.
Sticky exudate can cause dermatitis in humans and stain clothing.

Symptoms:

Excitement, distrust, tendency to charge, trembling, stilted gait, staggers, loss of muscle control, exaggerated bending of front legs if forced to run, may lose balance and drop suddenly if startled, frothing at the mouth, discharge from nostrils and eyes, increased heart rate, reddening of skin, soreness of muzzle, feet and teats, fall down with tetanic spasms, teeth grinding and occasional violent kicking. Animals usually die by misadventure or drowning in waterholes rather than direct toxicity.

Treatment:

Remove stock quietly from infected paddocks if in the early stages of poisoning. Recovery usually takes a few days. In the later stages of poisoning moving stock may bring on more serious symptoms.
Treatment with 350-400 g Epsom salts is occasionally suggested.
Graze paddocks heavily next season, mow or 'Spray Top' to reduce seed head formation.

Legislation:

None.

Management and Control:

Heavy continuous grazing usually provides control.
It is tolerant to mowing and occasional cultivation.
Clean clothing and prevent animals moving through infested areas when ripe seed is present as it adheres to fur and material. Clean mowers and machinery before leaving infested areas.
In cropping areas, Paspalum can usually be reduced to insignificant levels by using glyphosate for spray topping, summer weed control and pre plant weed control.
A typical program would be heavy autumn grazing followed by heavy grazing in late winter to spring with stock being removed when the annual grasses start to elongate in spring. When the heads of annual grasses just start to emerge Spraytop with 800 mL/ha glyphosate(450g/L) followed by 800 mL/ha 4 weeks later. If summer weeds emerge then spray with glyphosate at a rate appropriate for the weeds. In autumn spray annual weeds when they have reached the 2 leaf stage with about 2 L/ha glyphosate(450g/L). Rates should be adjusted so that a total of 3-4 L/ha glyphosate is applied over the 2-4 sprays. This will give results similar to applying 6 L/ha as a single application. Cultivation, 2-10 days after spraying with a scarifier or using a tyned full cut seeder to plant the crop will provide improved control compared to minimum tillage planting.

Thresholds:

Eradication strategies:

Apply glyphosate in autumn and spring each year.
Small plants can be manually removed providing all the rhizome is taken. Larger plants are more difficult.
Swards can be mown with a catcher a few days before treating with glyphosate to reduce seed banks.
In sensitive areas the tops may be cut and bagged and the base sprayed or wiped with glyphosate.
If removing manually ensure the rhizome and crown of the plant is removed and burnt.
Seed adheres to clothing and machinery so ensure that seed is removed before leaving the infestation.
Burning is not generally effective because it tends to grow in wet areas. In drier areas, burning followed by spraying the regrowth with glyphosate is effective and often reduces damage to companion plants by reducing the amount of leaf that is present at spraying.

Herbicide resistance:

Biological Control:

A fungus often attacks the seeds.

Related plants:

Plicatulum (Paspalum plicatulum)
Russell River grass (Paspalum paniculatum)
Saltwater Couch (Paspalum distichum)
Saltwater Couch (Paspalum vaginatum)
Scrobic (Paspalum scrobiculatum)
Sourgrass (Paspalum conjugatum)

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). P50-51. Photo.

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P227. Diagram.

Blood, K. (2001). Environmental weeds: a field guide for SE Australia. (CH Jerram & Associates, Australia). P216. Photo.

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P63, 65. Diagram.

Ciba Geigy (1980) Grass Weeds 1. CIBA GEIGY Ltd, Basle, Switzerland. P96. Diagrams.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P127. Photo.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P334.

Gardner, G.A. and Bennetts, H.W. (1956). The toxic plants of Western Australia. (West Australian Newspapers Ltd, Perth). P2.

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). P62-63. Photo.

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). #938.3.

Moore, J.H. and Wheeler, J.R. (2002). Southern Weeds and their Control. Photos.

Muyt, A. (2001). Bush Invaders of South-East Australia: a guide to the identification and control of environmental weeds found in South East Australia. (R.G and F.J. Richardson, Australia). P78-79. Photos.

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). P973.

McBarron, E.J. (1983). Poisonous plants. (Inkata Press, Melbourne). P3.

Paterson, J.G. (1977). Grasses in South Western Australia. (Western Australian Department of Agriculture Bulletin 4007). P68.

Acknowledgments:

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