Noogoora burr (Xanthium strumarium) consists of two species: X. Occidentale (Noogoora burr) and X. Californicum (Californian burr). Both weeds are annual plants that are very similar in appearance and ecology.
- erect annual herbs to 2.5m with two growth forms – either erect single stemmed plants or many branched spreading plants
- leaves are dark green and similar in shape to grapevine leaves, 15cm in diameter
- stems are blotched or streaked with purple
- flowers are green, in inconspicuous clusters
- fruit is a hard woody burr with many hooked spines around the body and beak-like points at the ends
- the beaks (Noogoora burr) are 2mm long and straight, and the beaks (Californian burr) are slightly longer and curved, each burr contains two seeds 6-10mm long.
Why is it a problem?
- wool processors will generally reject wool infested with the burrs of this plant
- spines cause physical damage to stock, people and shearing machinery
- competes strongly with summer crops and pastures due to its extensive root system and rapid growth
- the plants may also carry crop and vegetable diseases
- seedlings are poisonous to stock, particularly cattle and pigs, the toxin is carboxyatractyloside
- also causes dermatitis and hayfever in humans and animals.
- Eyre Peninsula – isolated plants
- Northern pastoral – common in eastern districts, isolated patches in northern
- Pastoral areas
- Northern agricultural districts and Yorke Peninsula – small isolated infestations particularly around watercourses near the NSW border
- Murray Mallee – scattered along the Murray River
- South East – isolated plants
- Central region – isolated outbreaks along watercourses.
- both burrs prefer moist areas such as the edges of waterways and damp depressions, but not permanently waterlogged soil
- seeds of both species germinate towards end of spring after rain or irrigation
- burrs form between February and May
- late germinating plants can produce burrs at a very early age
- plants die in late autumn but remain standing, carrying mature burrs for many months.
How it spreads
- hooked spines on the burrs are well adapted to clinging to wool and fur
- burrs are also easily transported by clothing, packaging and water.