Invasiveness Assessment - Bathurst burr (Xanthium spinosum) in Victoria (Nox)

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Plant invasiveness is determined by evaluating a plant’s biological and ecological characteristics against criteria that encompass establishment requirements, growth rate and competitive ability, methods of reproduction, and dispersal mechanisms.

Each characteristic, or criterion, is assessed against a list of intensity ratings. Depending upon information found, a rating of Low, Medium Low, Medium High or High is assigned to that criterion. Where no data is available to answer a criterion, a rating of medium (M) is applied. A description of the invasiveness criteria and intensity ratings used in this process can be viewed here.

The following table provides information on the invasiveness of Bathurst burr.

A more detailed description of the methodology of the Victorian Weed Risk Assessment (WRA) method can be viewed below:

Victorian Weed Risk Assessment (WRA) method (PDF - 630 KB)
Victorian Weed Risk Assessment (WRA) method (DOC - 1026 KB)
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Common Name: Bathurst burr
Scientific name: Xanthium spinosum

Question	Comments	Reference	Rating
Establishment
Germination requirements?	“Several germination’s occur after late spring and summer rains or after irrigation”. “In Australia, some seeds germinate out of season”.	P & C (1992 p. 319)	H
Establishment requirements?	“Bathurst burr grows best in open, unshaded areas”.	H & L (1995 p. 258)	ML
How much disturbance is required?	Invades minor disturbed ecosystems, (e.g. lowland grassland and grassy woodland and rock outcrop vegetation).	Carr et al (1992)	MH
Growth/Competitive
Life form?	Erect annual herb. Other.	P & C (1992 p. 318)	L
Allelopathic properties?	No Allelopathic properties described.		L
Tolerates herb pressure?	“In some areas stock seem to relish Bathurst burr seedlings…more mature Bathurst burr plants are not palatable to stock”.	H & L (1995 p. 277)	MH
Normal growth rate?	“Competes strongly with many summer crops”. “Capable of forming extensive dominant stands under suitable conditions”.	P & C (1992 p. 320) H & L (1995 p. 257)	H
Stress tolerance to frost, drought, w/logg, sal. etc?	“It grows in drier conditions than Noogoora burr, but succumbs to water logging”. Tolerates drought and frost (occurring in areas of Australia that experience both). However assumed to tolerate some water logging as occurs in seasonal fresh water wetlands. (Carr et al 1992). Also likely to tolerate some salinity as the closely related Noogoora burr is moderate to quite high. (H & L 1995 p. 262).	H & L (1995 p. 256) P & C (1992 p. 318)	MH
Reproduction
Reproductive system	“Reproducing by seed”. Male and female flowers on same plant.	P & C (1992 p. 318) Hocking & Liddle (1995 p. 246)	ML
Number of propagules produced?	“Two seeds are produced in each burr”. If 100 burrs per plant = 200 seeds per plant. “About 150 burrs are produced per plant”.	P & C (1992 p. 321) H & L (1995 p. 266)	ML
Propagule longevity?	“Some seed remains dormant in the soil for at least three years”.	P & C (1992 p. 321)	L
Reproductive period?	Annual.	P & C (1992 p. 318)	L
Time to reproductive maturity?	Annual.	P & C (1992 p. 318)	H
Dispersal
Number of mechanisms?	Refer to ‘dispersal’ in P & C (1992 p. 319 & 320). animals, clothing and contaminated seeds.	P & C (1992 p. 318)	MH
How far do they disperse?	“Well adapted for dispersal because the hooked spines on the burrs cling firmly to the wool or fur of animals…”.	P & C (1992 p. 319)	H

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