Quick Facts

Quick facts

  • Originally from the Americas, Spiny Burrgrass (Cenchrus spinifex) is an tufted upright or spreading grass growing to about 60 cm tall, with flat-folded leaves to 20 cm long and spiny burrs.
  • It is found mostly in sub-tropical, semi-arid and warmer temperate climates, mostly in Queensland and New South Wales but is also found in all other mainland states.
  • Spiny burrs can injure animals mouths, and also people.
  • It spreads by burrs which become attached to animals, vehicles, clothing, and in contaminated agricultural produce, soils and gravel.
  • Control methods for this annual to short lived perennial grass should aim to prevent seed set.
  • Can be controlled by physical removal, cultivation, and herbicides.

What Does It Look Like?

What is it?

Spiny Burrgrass (Cenchrus spinifex) [as Cenchrus incertus] is an upright tufted or spreading annual, or occasionally biennial or perennial grass,  that regrows from a crown. It usually growing to about 60 cm tall, but sometimes reaching up to 80 cm in height, sometimes with pink0reddish colour at the base of the stem. The narrow leaf blades are 2, 5 cm sometime to 20 cm long and 2–8 mm wide, flat-folded or in-rolled, and are mostly smooth and hairless. Leaf sheaths (part of the leaf rolled around the stem) are hairless or sparsely hairy. A ligule (a small appendage on the top of the leaf sheath where sheath meets the leaf blade) is a fringe of tiny hairs 1–2 mm long. 

The flower (seed-head) is spike-like in appearance and is often partially enclosed within the uppermost leaf sheath and and composed of 10–40 spiny  'burr-like' structures 2–5 mm long, mostly densely packed on stem, but sometime interrupted with stem between burrs. the spiny burrs are hairless, with spines all flat, the longest to 4 mm long. Burrs contain a cluster of two to four flower spikelets and each flower spikelet usually produces a single seed. Burrs are reddish or purplish-green colour when young but turn straw-coloured or brown as they mature. Flowering occurs mostly during summer and autumn.

The fruits are 'burrs' which are 3–10 mm across, each with usually 10–40 sharp spines that are 3.5–5.5 mm long and have relatively broad bases. These 'burrs' are almost stalkless or borne on very short stalks 0.5–2 mm long, and when ripe they usually detach from the flowering stem entirely. The smooth seeds are 2–4 mm long by 2–3 mm wide and are egg-shaped, but flattened on one side, and remain well hidden within the burrs (Navie 2004).

For further information and assistance with identification of Spiny Burrgrass, contact the herbarium in your state or territory.

Flower colour

Red, Purple, Green, White, Brown

Growth form (weed type/habit)


Where it currently grows? Preferred habitat

Spiny Burrgrass is found mostly in sub-tropical, semi-arid and warmer temperate climates. This species is a weed of disturbed sites, waste areas, roadsides, pastures and cultivation. It prefers sandy soils (Navie 2004).

Are there similar species?

Spiny Burrgrass is very similar to another species also known as Spiny Burrgrass (Cenchrus longispinus), Mossman River Grass (Cenchrus echinatus) and Buffel Grass (Cenchrus ciliaris). 

The burrs on Spiny Burrgrass (Cenchrus longispinus) while also having several rows of larger flattened spines, usually with 40–70 spines in total. The burrs on Mossman River grass (Cenchrus echinatus) do not have stalks and only have one row of larger flattened spines. 

Buffel Grass (Cenchrus ciliaris) has seed-heads that do not produce spiny 'burrs'. Instead, its seed-heads bear flower spikelet clusters that have numerous long stiff bristles (Navie 2004).

Why Is It A Weed?

What are its impacts?

Agriculture: Spiny Burrgrass burrs cause a range of problems such as injury to people and dogs. The burrs can become badly tangled in wool thereby lowering its value. There is an economic cost as the burrs slow down shearing resulting in overtime penalty rates as working with contaminated wool requires leather gloves and/or aprons adding to the cost of production. Spines can cause injury to stock resulting in swellings and ulcers in the mouth, and they easily puncture the skin of animals thus affecting the value of hides. Fruiting plants are an inconvenience to agricultural workers of irrigated crops especially when working in vegetable, vine, citrus and tobacco crops, with burrs contaminating dried fruit crops and lucerne hay (Parsons & Cuthbertson 2001). Although easily controlled in lucerne, burr contamination can reduce the value of lucerne hay. As it is spring-summer growing, innocent weed is not a competitor with the major broad acre-crops.

Urban areas: It also infests some urban areas as a weed of footpaths, bare street-scapes and recreation grounds, although it is less of an issue in maintained gardens and lawns (Government of South Australia 2021).  

How does it spread?

Spiny Burrgrass reproduces by seeds, which are contained within spiny 'burrs'. These 'burrs' are most commonly spread when they become attached to animals, vehicles and clothing, but may also be dispersed by water and in contaminated agricultural produce and on machinery (Navie 2004).

What is its history in Australia?

Spiny Burrgrass' history in Australia is unclear partly because of uncertainty over identification, as it is easily confused with Spiny Burrgrass (Cenchrus longispinus). Plants were recorded in South Australia in 1886 and were recorded in Victoria in 1895. It was first reported in New South Wales in 1922 and Queensland in 1930 (Parsons & Cuthbertson 2001). The first Herbarium  records are from South Australia in 1910; Northern Territory in 1913; New South Wales in 1921; Queensland in 1930; Western Australia in 1956; Victoria in 1966; and Australian Capitol Territory in 1987 (AVH 2021).

How To Manage It?

Best practice management

Spiny Burrgrass can be controlled by physical and chemical means.  Prevention of seedlings is the key to successful control. Good hygiene practices such as cleaning of machinery and vehicles also aids in controlling spread (Mullen et al. 2005). Once established in dryland areas, innocent weed is very difficult to control because seed may remain viable in the burrs for at least five years. Some seed readily germinates after summer rains, but others in the same burr will remain dormant to germinate later, even skipping a year if there is a shortage of rain in late spring and summer (Government of South Australia 2021). 

Non-chemical control: Preventing seeding is the key to successful control. This can be achieved by cultivation before seed formation, preferably at the seedling stage as larger plants are difficult to turn completely over. Repeated cultivation is necessary to kill subsequent seedlings. Heavy grazing by sheep also prevents seedlings but is not always practical. Well managed pastures can out-compete and exclude establishment of Spiny Burrgrass.

Chemical control: Application of herbicides to actively growing plants is effective (Parsons & Cuthbertson 2001). Innocent weed can generally be controlled in most irrigated and horticultural crops to prevent contamination of produce, but due to several germination events in one season, repeat treatments may be needed during the growing season. Control of broad acre infestations by herbicide can be prohibitively expensive compared to the income produced from the land. A number of herbicides provide control.

Please see Invasive Species Unit, Biosecurity SA (2018); DPI NSW (2019); the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au 

Does it have a biological control agent?


When does it grow? (lifecycle/growth calendar)

Spiny Burrgrass germination mostly occurs in spring and early summer, but may occur at any time of the year except mid-winter. Vegetative growth is rapid during the growing season if ample moisture is available. Burrs are produced from December to April. Most plants die in autumn or early winter, however some may survive over a mild winter and produce a further small crop of burrs in spring. In some areas it becomes a perennial, regrowing from a crown each spring (Parsons & Cuthbertson 2001).

Where Is It Found?

Which states and territories is it found?


What areas within states and territories is it found?

Spiny Burrgrass is a widespread species that is largely found in eastern Australia and is most common in the sub-coastal regions of northern New South Wales and south-eastern Queensland. It has a scattered distribution throughout the coastal regions of Western Australia, other parts of New South Wales and south-eastern South Australia. It is also recorded in Victoria, the Australian Capital Territory and the Northern Territory (Navie 2004). It is currently absent from Tasmania (AVH 2021).

Where does it originate?

Spiny Burrgrass is native to North America and Central America (Navie 2004).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?


Where is it a declared weed?


Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?


Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?


Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Cenchrus spinifex

Other scientific names (synonyms)?

  • Cenchrus incertus M.A.Curtis
  • Cenchrus pauciflorus Benth.
  • Cenchrus tribuloides L. (misapplied by Black, J.M. 1943, Flora of South Australia Edn 2. 1: 76.)

Does it have other known common name(s)?

Spiny Burr-Grass, Spiny Burr Grass, Burr Grass, Innocent Weed, Gentle Annie, American Burrgrass, American Burr Grass, Lesser Burrgrass, Spring Burrgrass, Burrgrass, Sandburr, Coastal Sandbur, Coast Sandbur, Coast Sandburr, Coast Sandspur, Dune Sandburr, Field Sandburr, Field Sandbur, Field Sandspur, Mat Sandbur, Longspine Sandbur, Sandbur, Sandbur Grass, Bayonet Grass, Field Burr, Hedgehog Grass

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