Quick Facts

Quick facts

• Originally from South America, Bathurst Burr (Xanthium spinosum) is a annual herb up to 1 m tall, each leaf is armed on the stem with rigid long 3-pronged spines, with many greenish flowers and hooked spiny oval fruits.
• A major weed of disturbed soil, flood plains and the agricultural land of Australia and an important cause of vegetable contamination of wool.
• It is present in all states and territories.
• It is easily recognisable by its spiny stems and burrs and green leaves with obvious white veins.
• It is dispersed readily by animals, stock, water,  people and machinery or agricultural produce.
• Young seedling plants are poisonous to stock.
• Controlled by herbicides, slashing and cultivation and good management of pastures and crops.

What Does It Look Like?

What is it?

Bathurst Burr (Xanthium spinosum) is an annual multi-stemmed herb to 1 m high. Stems are pubescent (downy; covered with short, soft, erect hairs) and on the stem at the base of each leaf is 1 or 2 rigid 3-pronged yellowish sharp spines 7–25 mm long. Leaves are narrow-rhombic (like a rhombus, with four equal sides) to lanceolate (lance-shaped,  about 4 times as long as broad, broadest in the lower half and tapering to the tip) in outline, mostly 20–80 mm long, 8–25 mm wide. Leaves are normally, 3-lobed, occasionally 5-lobed to occasional simple (not obviously lobed). Above the leaves are dark green prominently veined with 1 or 3 main whitish veins and sparsely hairy above. Below leaves are whitish to silver felted. Leaf tip sharply pointed (converging edges making an angle of less than 90°; acute), tapering  at base (cuneate), leaf stalked to about 10 mm long.

Flowers are uni-sexual with separate male and female flowers on the same plant. Male flowers are Flower-heads (capitula) clustered at end of branches, or in the upper leaf axils. Male flowers are pale or creamy green, often with blackish lobes, surrounded by clustered involucral bracts (modified leaves) that are ovate  (egg-shaped with widest end at the base) to obovate (egg-shaped with widest end at the tip), 1–2 mm long, with rusty-coloured hairs. Flowers (florets) are about as long as bracts,. Female flower-heads (capituala) are usually solitary in the leaf axils,  yellowish green to brown. 

Fruits are burrs are 10-12 mm long, with glandular and non-glandular hairs, numerous hooked spines, 2–3 mm long, and beaks 1–2 mm long (see Parsons & Cuthbertson 1992; Navie 2004).

For further information and assistance with identification of Bathurst Burr contact the herbarium in your state or territory.

Flower colour

Green

Growth form (weed type/habit)

Herb

Where it currently grows? Preferred habitat

Bathurst Burr is found in exposed, moderately warm situations in temperate regions on high fertility disturbed soils, and is often associated with sheep camps, watercourses, dam banks and floodplains (Parsons & Cuthbertson 1992). It is also present in disturbed semi arid to arid areas after rains or floods. It is a serious competitor with crops such as cotton, maize, peas, potatoes, soybeans, sorghum and grapes (Parsons & Cuthbertson 1992). Bathurst Burr invades lowland grassland and grassy woodland, riparian vegetation, freshwater wetland, and rock outcrop vegetation (Carr et al. 1992).

Are there similar species?

Bathurst Burr may be confused with Noogoora Burr (Xanthium strumarium), another common weed throughout Australia. Both species have similar looking burrs covered with hooked spines. They can be easily separated as Bathurst Burr has three long sharp spines on the stem at the base of each leaf, while Noogoora Burr is spineless on the stem. Bathurst Burr also has narrow adult leaves 8-22 mm wide, while Noogoora Burr has broad adult leaves, usually 50-150 mm wide (see Navie 2004).

Bathurst Burr may also be confused with Cockleburr (Xanthium spinosum) [as Xanthium ambrosioides]. Cockleburr has smaller, generally narrower leaves (2-4 cm long by 3-10 mm wide) which usually have three elongated lobes. Both leaf surfaces are finely hairy (i.e. pubescent) and greyish-green in colour. Its stems bear three-pronged spines near the leaf bases and its small fruit (4-8 mm long) usually do not have 'beaks', although occasionally one small 'beak' is present (see Navie 2004).

Why Is It A Weed?

What are its impacts?

Bathurst Burr was included in the list of 71 species that were nominated by state and territory governments for assessment as Weeds of National Significance (WONS). Following an assessment process, Bathurst Burr was not included as one of the 20 WONS. However, it remains a weed of potential national significance. It is a significant weed of agriculture and occurs in roadsides, water courses, waste areas, and rangelands

Agriculture: Bathurst burr is mainly a pasture and rangeland weed, but also a weed of summer crops and horticultural crops. In the rangelands it is common in sandy creek lines and areas that flood. It is also found in summer growing crops such as soya bean and maize, and can be a significant weed of crops such as cotton, peas, potatoes, sugarcane and grapes. Burrs are an important cause of vegetable contamination of wool in wool growing areas, making fleeces harder to work with and reducing their value and causing problems for shearers. Seedlings are poisonous specially the cotyledons (seed leaves) to livestock, particularly horses and pigs, however older plants are not eaten. It is not such a major weed in the higher rainfall areas as it is a poor competitor, establishing mainly in bare disturbed sites, after floods or on fallows. It does not tolerate dense competition from other weeds or dense pasture. It has been widespread in the more marginal pasture areas for over a century (Government of South Australia 2021).

Native ecosystems: Bathurst Burr also invades lowland grassland and grassy woodland, riparian vegetation, freshwater wetland, and rock outcrop vegetation (Carr et al. 1992). Dense populations could have a major impact on herbs and grasses in native vegetation (DPI 2007).

Urban areas: Invades roadsides, watercourses and waste areas (DPIW 2007). Some people may develop dermatitis after contact with the plant (Parsons & Cuthbertson 1992).

How does it spread?

The burrs of Bathurst Burr are covered in hooked spines and attach readily to livestock, clothing, and are spread in mud and soil. They also float on water and are readily carried along water courses and across flood plains (Parsons & Cuthbertson 1992).

What is its history in Australia?

Bathurst Burr was introduced to Australia allegedly tangled in the tails of horses imported from Chile in the early 19^th Century; it may also have entered as a grain contaminant. It became established in New South Wales, including Bathurst, and was observed by John Macarthur in the early 1830s on the Nepean River. By the 1850s it was the cause of public concern. It was proclaimed a noxious weed in 1856 in Victoria and 1862 in South Australia. By 1895, the dramatic and invasive nature of this weed in eastern Australia, led to it being described as New South Wales' worst weed (Parsons & Cuthbertson 1992).

How To Manage It?

Best practice management

General management of Bathurst burr (Xanthium spinosum) is primarily targeted to prevent seed generation. An integrated approach to managing Bathurst Burr should therefore be implemented which eliminates existing plants by spraying or grubbing then establishing competitive pasture to help prevent new plants from establishing (DPIW 2007). Eradication of Bathurst Burr requires the prevention of seeding for at least four to six years and the elimination of sources of reinfestation (Faithfull 1998). Some seeds may remain viable for up to eight years (Anon. 2007).

Chemical control:  Bathurst Burr is susceptible to some herbicides, particularly on young plants. Bathurst burr is highly visible when growing, and control in pasture is readily achieved by commonly used selective herbicides, or spot spraying small infestations with non-selective herbicides (Government of South Australia 2021). Spraying should be carried out before the burrs have formed. Pasture improvement combined with herbicide treatment is the favoured method of control in grazing lands (Land Protection 2006). Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au .

Non-chemical control: Physical control: Removal by hand is not recommended due to the sharp spines. Small infestations are best dealt with by hoeing or grubbing / chipping and is only economical for small areas, individual plants or isolated populations. It is also an effective follow up control method for plants not controlled by other methods to prevent seed set. Plants carrying burrs should never be dumped, as the seed may be easily spread but should be gathered and burned.

Mechanical control: Repeated cultivation of seedlings after each germination event is effective on arable land. Mechanical slashing should be undertaken before the burrs have formed (Faithfull 1998). Successive flushes of seedlings during the summer may require follow up control. Inter-row cultivation is commonly used in row cropping such as sorghum, corn and cotton to control seedlings that have germinated after irrigation events (DPI NSW 2019).

Competition and management: Strong competition, particularly from a well managed pasture containing legumes, will greatly inhibit the successful establishment of Bathurst Burr.  Adult plants are not easily eaten by livestock, due to the roughness of the leaves and stems and care needs to be taken when grazing to ensure there are no seedling plants, which are toxic to animals and could result in death (DPI NSW 2019).

Biological control: An indigenous Australian Blight Fungus (Colletotrichum orbiculare) occurs on some infestations and is being developed by New South Wales Agriculture as a mycoherbicide. The accidentally introduced rust fungus (Puccinia xanthii) affects both Noogoora Burr and Bathurst Burr. The Bathurst Burr seed fly (Eurraresta bullans) was introduced from South America in the 1920s and affects large areas of burr in New South Wales and Queensland but provides no long term control (Faithfull 1998).

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Each burr contains two brown, flattened seed about 9 mm long, one of which is capable of immediate germination, but the second may stay dormant in the soil for several years. Dormancy depends on the permeability of the seed coat. This is broken down by high temperatures. Germination may also be controlled by day-length and daytime temperatures. The result is a staggered germination which makes Bathurst Burr seedlings difficult to control and allows the plant to exploit the variable environmental conditions under which it grows (Department of Agriculture and Food undated).

Of the two seeds in each burr, one germinates the first spring or summer and the other does not germinate until the second or third year. Some seeds may remain viable for up to eight years (Anon. 2007).

Where Is It Found?

Which states and territories is it found?

Found in all Australian states and territories.

What areas within states and territories is it found?

Bathurst Burr is present in all states and territories of Australia. It is widespread in Queensland, New South Wales, Victoria and eastern South Australia. While it is widespread in southern, western and central areas of Queensland, it is seldom important in the tropics.

It is less common in Tasmania, where it is only found near a few wool mills and abattoirs. 

In the Northern Territory it is confined to the Alice Springs area. 

In Western Australia, where it is confined to a few places in the south-west around Perth, York and further south. It is also present in the Goldfields region around Kalgoorlie and stretches further eastwards into the southern desert regions of Western Australia (Parsons & Cuthbertson 1992; Faithfull 1998; Land Protection 2006; DPIW 2007).

Bathurst Burr also occurs as a weed in most temperate areas of the world, including the Mediterranean, the British Isles, Africa, North America and New Zealand. It has spread to 39 countries in these regions (Parsons & Cuthbertson 1992).

Where does it originate?

Bathurst Burr is native to South America (Weeds Australia).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

NT, SA, VIC, WA

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Xanthium spinosum

Other scientific names (synonyms)?

Xanthium ambrosioides Hook. & Arn.

Does it have other known common name(s)?

Spiny Cocklebur, Spiny Burweed, Spiny Clotbur, Dagger Cocklebu, Daggerweed, Prickly Burweed, Thorny Burweed