Bathurst Burr

Xanthium spinosum L.

Family: Asteraceae.

Names:

Xanthium is from the Greek xanthos meaning yellow and refers to its ancient use as a yellow hair dye.
Spinosum is Latin for spiny referring to the spines on the stems.
Bathurst Burr because the seed is enclosed in a burr and it was introduced to Bathurst around 1850 trapped in the tails of horses imported from Chile.

Other names:

Boetebossie (South Africa)
Burrweed (South Africa)
Common Cocklebur
Pinotiebossie (South Africa)
Prickly Burrweed
Spiny Clotbur (USA)
Spiny Cocklebur (UK, USA, South Africa)

Summary:

An erect, hairy, compact often bushy annual shrub with divided dark green leaves that are whitish underneath. The stems have long, yellow three-pronged spines.

Description:

Cotyledons:

Two. Elongated oval shaped, 20-25 mm long with a round tip. It has a short petiole. The hypocotyl and epicotyl are short.

First leaves:

Narrowly triangular, 25 mm long x 15 mm wide, dark green on top, whitish, due to short hairs, on the underside. with a long distinct petiole.

Leaves:

Alternate.
Stipules - None.
Petiole - 10 mm long with 1-2 three-pronged spines at the base.
Blade - Narrowly egg shaped to narrowly rhomboidal, 20-100 mm long x 10-30 mm wide, 1-5 irregular lobes, often 3 lobed with a long narrow end lobe, smooth edged, shiny dark green on top drying blackish, whitish-hairy underneath. Sparse low lying hairs on the upper surface with dense hairs on the veins, densely hairy on the lower surface except on the veins. Obvious whitish or light green veins.
Stem leaves - 3 lobed with a distinctive pale marking along the centre vein.

Stems:

Erect, coarse, rigid, round, 500-1500 mm tall, often yellowish, often curved, faintly striped, usually branched but may be unbranched in small plants becoming somewhat woody with age with 1-2, yellow, three-pronged, 15-25 mm long, spines is at the base of the petioles and branches. Sparsely hairy.

Flower head:

Unisexual, inconspicuous.
Male flower heads (involucre) globular, 4-5 mm diameter with 1 row of free bracts in the upper leaf axils and separate from the females.
Female flower heads (involucre) egg shaped, 2 flowered, several rows of bracts with lowest row free and the upper rows forming a spiny burr when in fruit and usually single in the lower and upper leaf axils.

Flowers:

Inconspicuous, greenish white.
Bracts - see above.
Florets - Narrow, tubular.
Ovary - Receptacle is hemispherical with narrow, chaffy scales. Style with two long slender, acute tipped, flattish branches that stick out at the base of the two beaks when in fruit.
Perianth - 5 lobed.
'Petals' - None. Corolla tubular in male flowers and absent in female flowers.
Stamens - Filaments joined.
Anthers - 5, free, obtuse base, small appendage on top.

Fruit:

Light brownish, oval to oblong or egg shaped, stalkless burr, 8-15 mm long x 4-5 mm wide with 2 seeds (achenes) and many, yellow hooked spines plus 0-2 straight inconspicuous beaks (horns), shorter than the spines, at the top. Hairy except on the spines.

Seeds:

Brown to black, 10 mm long with one slightly larger than the other, enclosed in egg shaped to cylindrical, flattened achenes, which are enclosed in the burr.

Roots:

Branched taproot.

Key Characters:

No milky sap.
Leaves alternate, 3 branched spines below, leaf blades much longer than broad.
Head unisexual, monoecious.
Female head 2 flowered with no corolla, involucre bracts connate about the florets enclosing the fruiting head and forming a hard, dehiscent, nut like receptacle with the tips of the bracts forming hooked spines.
Male heads discoid.
Involucre bracts of male heads free.
Florets tubular, not ligulate.
Receptacle with chaffy scales.
Style branches flattish.
Corolla tubular in male flowers, absent or reduced in females.
Anthers free, obtuse at base.
Fruit a spiny ovoid burr.
No pappus.
Adapted from J.M. Black, N.T. Burbidge and N.S. Lander.

Biology:

Life cycle:

Annual. Seed germinates in the spring and summer often after rains or irrigation and it grows rapidly during the summer and early autumn. Fruit can usually be found on the plants by December and it continues flowering in to the autumn. It usually dies by winter. A few plants often germinate and grow out of season with the main population. Late germinating plants generally flower within a few weeks.
In Tasmania, circumstantial evidence suggests that in sheltered areas plants can survive for more than one season.

Physiology:

Reproduction:

By seed.

Flowering times:

Summer to autumn in western NSW.
February to July in SA.
January to May in Perth.
January to June in WA.

Seed Biology and Germination:

Some seed may remain dormant for several years. It can germinate and survive in drier conditions than Noogoora Burr (Xanthium spinosum).

Vegetative Propagules:

None.

Hybrids:

Allelopathy:

Contains toxins that reduce the growth of companion plants.

Population Dynamics and Dispersal:

It is distributed mainly by sheep carrying burrs in their fleece and burrs floating along watercourses. The spiny burrs readily entangle in fur and fabric. Burrs have been seen on second hand bags and woolpacks and in mud on vehicles.
It is also spread by native animals, in agricultural seeds and produce, bird seed and by earth moving operations.
They readily colonise disturbed areas.

Origin and History:

South America, possibly Chile.
Introduced to Bathurst about 1850 trapped in the tails of horses imported from Valparaiso in Chile. It may also have been imported to NSW as a contaminant of grain planted before 1830 near the Nepean river
Introduced to Tasmania as a fleece contaminant and in parrot seed.
It was a noxious weed of Victoria by 1856 and South Australia by 1862.
Pronounced as the worst weed in NSW in 1895.

Distribution:

ACT, NSW, NT, QLD, SA, TAS, VIC, WA.
It is common in the eastern goldfields in WA with occasional plants found in the wheatbelt.
Small isolated infestations have been found in various parts of Tasmania and are usually eradicated. Widely distributed in mainland Australia.
Often found near aviaries, abattoirs and near premises used for wool handling.

Courtesy Australia's Virtual Herbarium.

Habitats:

Prefers open situations.

Climate:

Temperate.

Soil:

Most soils.
More abundant on fertile, periodically flooded soils and clay flats which retain moisture after summer rains.

Plant Associations:

Significance:

Beneficial:

Used in herbal medicine in the past for hydrophobia and treating fevers.
Source of yellow dye.

Detrimental:

Weed of summer crops, vegetables, pasture, stock yards, cultivation, fallows, roadsides, channel banks, dry streams, dam banks, bores and disturbed areas.
One of the worst causes of vegetable fault in wool. The fruit is covered in hooked spines and becomes entangled in the fleece especially around the neck and belly. This means the fleece requires more skirting resulting in lower returns to the wool grower. It is not as difficult to remove from wool as Noogoora or California Burrs but contaminated wool may still require carbonisation.
Interferes with shearing by jamming hand pieces and irritating the skin of the shearers.
Interferes with the harvest and handling of summer vegetable crops.
Rarely grazed.
Dense infestations can reduce stock movement.
Reduces the yields and choice of rotations in crops.
Contains toxins that reduce the growth of companion plants.

Toxicity:

Seedlings are probably toxic but field cases are rare.
Stock forced to graze it may develop gastro enteritis and diarrhoea.
Poultry may moult early and have reduced egg production if given feed contaminated with Bathurst Burr.
Stock feet are injured by the burrs, which may lead to infection.
People can get dermatitis from contact with the plant.

Legislation:

Declared plant that is under an eradication program in WA.
Noxious weed of ACT, NSW, NT, QLD, SA, TAS, VIC, WA.

Management and Control:

Cultivation provides effective control of vegetative plants but must be repeated each time seedlings appear. Burning, mowing and slashing are also effective in some situations. Hormone herbicides provide good control of young actively growing plants and there are several selective herbicides available for a number of crops.

Thresholds:

Less than 1 plant/m2 is usually worth spraying.

Eradication strategies:

Check all imports of stock, fodder, grain, produce and bags for burrs. Prevent seed set. Don't allow stock and especially sheep to have access to infested areas when burrs are present.
Isolated plants should be manually removed and the area sprayed with a mixture of 1 litre of Tordon® 75-D in 100 litres of water each spring for several years.
The soil seed bank should be nearly exhausted in 4 years.
Control programs should start at the headwaters of catchments.
Establish competitive pasture species to reduce reinfestation.

Biological Control:

Occasionally attacked and killed by a caterpillar.
A fungus also attacks the seeds in some areas.

Related plants:

Bathurst Burr (Xanthium spinosum)
Californian Burr (Xanthium orientale)
Xanthium ambrosioides is similar but has downy leaves and smaller burrs.
Xanthium cavanillesii.
Xanthium italicum.

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). P120-122. Diagram, Photo.

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P874.

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P366. Diagram.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P727.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P194.

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). P108-109. Photo.

Hyde-Wyatt, B.H. and Morris, D.I. (1980) The Noxious and Secondary Weeds of Tasmania. (Tasmanian Department of Agriculture, Hobart, Tasmania). P20-21. Diagrams.

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). #1286.3.

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). P714.

Meadly, G.R.W. (1965). Weeds of Western Australia. (Department of Agriculture - Western Australia). P143. Photo. Diagram.

Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P318-321. Photos.

Wilding, J.L. et al. (1987). Crop weeds. (Inkata Press, Melbourne). P65. Diagrams. Photos.

Acknowledgments:

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