Caltrop

Tribulus terrestris L.

Family: Zygophyllaceae.

Names:

Tribulus is from the Greek tribolos meaning three pronged or the Latin tribo meaning to tear and also the Latin name of the caltrop. Both refer to the spiny fruit.
Terrestris is Latin meaning of the earth and refers to its ground hugging growth habit.
Caltrop is named after a medieval weapon; the small, four spiked, metal ball (a caltrop) that was laid to cripple enemy horses and infantry and is derived from the Old English coletraeppe which is derived from the Latin calx a heel and trappa, a trap, thus it is a heel trap. It refers to the spiny burrs.

Other names:

Bindii
Bindyi (NSW).
Bull Head
Burnut
Common Dubbeltje (South Africa)
Cathead (NSW)
Goathead
Goat-head Burr
Malta Cross (Europe)
Puncture Vine (NZ, UK,USA)
Yellow Vine

Summary:

A low lying, hairy annual herb or vine with opposite leaves with 3-8 pairs of leaflets and yellow, 5 petalled flowers at any time of year that form sharp spiny burrs.

Description:

Cotyledons:

Two. Narrowly oval. Tip round. Base indented. Hairless. Short petiole.

First leaves:

Arise as pairs of leaves with oval, pointed tip leaflets and long hairs.

Leaves:

Opposite and unequal size with 3-8 pairs of opposite oval leaflets.
Stipules - Narrowly egg shaped, small.
Petiole - Short.
Blade - Of leaflet, oblong with an oblique base, 4-12 mm long x 2-5 mm wide, rough to touch, upper surface is hairy on the midrib and edges whilst underneath they are hairy all over with low lying hairs. Upper surface dark green and paler beneath. Leaflets stalkless or very shortly stalked.

Stems:

Green to red-brown, low lying, up to 2000 mm long, round, many branched. Elongate in late winter. Short, soft, crimped and long bristly hairs and often becoming hairless with age. Forms a dense mat.

Flower head:

Single flowers in the axil of a smaller leaf.

Flowers:

Yellow, often hairy, 8-15 mm diameter. On short haired and rough to touch stalks.
Bracts -
Ovary - Superior, coarsely hairy, 5 celled. 2-5 ovules per cell. Stigma lobed.
Sepals - 5, green, narrowly egg shaped with a pointed tip, free, 3-6 mm long, hairy, overlapping.
Petals - 5, narrowly egg shaped, yellow, free, 5-15 mm long, overlapping.
Stamens - 10 with 2 stamens per petal. Filaments thread like.
Anthers - Oval in outline.

Fruit:

Star shaped, woody burr, 6-10 mm long that separates into 5 wedge shaped, prickles. Prickles (carpels) have 2 spreading spines, 3-8 mm long near the top and 2-3 smaller, bent back spines near the base, and tiny warts on the back. Sometimes hairy. Does not release seed.

Seeds:

Yellow, variably egg shaped, 2-5 mm long. 1-4 seeds enclosed in each prickle (carpel) and separated by partitions.

Roots:

Long, slender, branched, woody taproot and many fibrous laterals up to 2600 mm deep.

Key Characters:

Annual herb.
Leaves at least the upper ones opposite, pinnate with 3-8 pairs of leaflets, not aromatic.
Spines 2-4 on the back of each carpel.
Flowers bisexual.
Stamens 10.
Capsule separating into 5 hard, spiny, solid fruitlets.
Adapted from J.M. Black and J.R. Wheeler.

Biology:

Life cycle:

Annual or short lived perennial. Seed germinates from spring to autumn after rain and it grows rapidly producing deep roots. It grows mainly in the warmer months. It grows profusely after summer rains and flowers mainly in summer and autumn. The flowers open in the morning and close or drop their petals in the afternoon. They usually die in autumn or winter after the first frosts. In tropical areas the deep taproot develops and the plant becomes a perennial.

Physiology:

Frost sensitive.
Drought tolerant, waterlogging intolerant.
Grows best at high light levels.

Reproduction:

By seed.

Flowering times:

Any time of year in WA.
December to March in Perth.
Mainly summer and autumn in western NSW.
Winter and spring in SA.

Seed Biology and Germination:

Only one seed in each prickle germinates.
May remain viable in the soil for many years.
Seed germinates on the surface and up to 50 mm deep in sandy soils.
Few seeds will germinate soon after ripening but within 6 months 84% germination has been reported in seed free of the burr.
Requires warm temperatures for germination.

Vegetative Propagules:

Perennial taproot in tropical situations.

Hybrids:

Probably at least three forms, the spinier, less hairy form is probably introduced.

Allelopathy:

Probably inhibits the growth of grass seedlings.

Population Dynamics and Dispersal:

Spreads by burrs carrying seed that attaches to animals, tyres and fabric.
Rapidly invades denuded areas.
Plants can flower from 3 weeks old and have fruit at 5 weeks. It can produce 1000 burrs per plant.
It re shoots from the taproot if damaged.

Origin and History:

Sub tropical Australia. Europe. Africa, Asia.
It may have been introduced before European settlement.
Reported as a weed in NSW in the 1890's.

Distribution:

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

Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Temperate. Mediterranean. Sub tropical. Tropical. Warm Temperate.

Soil:

Occurs on a wide range of soils.
More abundant on sandy soils.

Plant Associations:

Significance:

Beneficial:

Honey plant.
Fodder.
Kills bacteria and used in herbal medicine as a diuretic, tonic and aphrodisiac. Chewed by northern Aboriginals to ease toothache.
May act as a growth promoting substance (Murugan et al, 1998)
Used as a potted ornamental.
Does not host Root Lesion Nematodes (Pratylenchus thornei)

Detrimental:

Weed of pastures, crops, vineyards, orchards, cotton, horticulture, roadsides, stockyards, bushland, parks, stock routes and disturbed areas.
Injures animal feet.
Contaminates wool.
Contaminates dried fruit.
Injures shearers and wool, fruit and vegetables handlers.
Relatively unpalatable.
Poor host of Root Lesion Nematodes (Pratylenchus neglectus) and allows some build up of numbers.

Toxicity:

Dense infestations may be toxic to stock causing photo sensitisation of skin around lips, ears and eyes followed by swelling of the head. Sheep are more commonly affected than cattle.
Causes a chronic staggers mainly in the British breeds of sheep.
Spiny burr may cause injury to feet and intestines of stock and form pussy sores where they penetrate the frog of horses hooves.
It can accumulate nitrate and oxalate levels high enough to cause nitrate poisoning and oxalate poisoning in stock especially after spraying with hormone herbicides like 2,4-D.

Symptoms:

Treatment:

Avoid grazing with horses, pigs and young or breeding stock.

Legislation:

Noxious weed of NT, SA, TAS, VIC and WA.

Management and Control:

Cultivation is not usually effective because of multiple germinations.
Herbicides provide the best method of control. A number of herbicides are effective in various crops and situations.

Thresholds:

Eradication strategies:

Remove isolated plants and surrounding soil and burn.
Spray the area until just wet with a mixture of 1 litre or Tordon® 75-D in 100 litres of water initially and each times seedlings appear. Plant a vigorous grass on the area.
On areas that can be left bare, such as around buildings and roads, treatment with diesel is effective.

Herbicide resistance:

Biological Control:

Bio control has been effective in some overseas locations and the larvae of a native moth occasionally cause damage in Australia. Its unclear status as a native plant and which forms are introduced make bio control in Australia unlikely in the near future.

Related plants:

Caltrop (Tribulus cistoides)
Perennial Caltrop (Tribulus eichlerianus = Tribulus occidentalis)
Spineless Caltrop (Tribulus micrococcus)
Tridax (Tribulus procumbens)
Yellow Vine (Tribulus micrococcus) is very similar but does not have spines on the burr.
Tribulus astrocarpus
Tribulus hystrix
Tribulus minutus

Plants of similar appearance:

Spiny Emex (Emex australis) also has a prickly burr but its has only 3 equal spines.

References:

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P238. Photo.

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P490. Diagram.

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P238-239. Diagram.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P438. Photo.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P761-764. Diagram.

Gardner, G.A. and Bennetts, H.W. (1956). The toxic plants of Western Australia. (West Australian Newspapers Ltd, Perth). P120-122. 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). P230. 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). #1224.5.

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). P491.

McBarron, E.J. (1983). Poisonous plants. (Inkata Press, Melbourne). P34. Diagram.

Meadly, G.R.W. (1965). Weeds of Western Australia. (Department of Agriculture - Western Australia). P104-106. Diagrams. Photo.

Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P640-643. Photos.

Wilding, J.L. et al. (1987). Crop weeds. (Inkata Press, Melbourne). P149. Diagrams. Photos.

Acknowledgments:

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