Invasiveness Assessment - English broom (Cytisus scoparius) 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 English broom.

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 - 1 MB)
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Common Name: English broom
Scientific name: Cytisus scoparius

Question	Comments	Reference	Rating
Establishment
Germination requirements?	“Seeds germinate in both autumn and spring”.	P & C (1992) p. 470	MH
Establishment requirements?	“Young plants survive even in 90% shade”.	P & C (1992) p. 470	MH
How much disturbance is required?	“Broom is found in grassland/woodland/open forest including a wide range of disturbed as well as undisturbed communities”.	Hocking et al (1998) p. 79	H
Growth/Competitive
Life form?	“Once established, English Broom fixes nitrogen in the soil”. Legume.	P & C (1992) p. 471	MH
Allelopathic properties?	Once established, English Broom fixes nitrogen in the soil, which inhibits the growth of native species adapted to nutrient poor soils.	McArthur (pers. Comm)	MH
Tolerates herb pressure?	Consumed by stock, (cattle, sheep, horses and goats), but not preferred.	McArthur (pers. Comm)	MH
Normal growth rate?	“Competing strongly with native species”. “Once established it dominates the vegetation of an area, smothering quite large shrubs”.	P & C (1992) p. 469 P & C (1992) p. 471	MH
Stress tolerance to frost, drought, w/logg, sal. etc?	“Tolerates frost, mature plants tolerate summer drought, mature plants generally killed by fire but may survive if intensity not great”.	Blood (2001) p.54/55	MH
Reproduction
Reproductive system	“Reproducing by seed”.	P & C (1992) p. 469	ML
Number of propagules produced?	“9650 seeds per plant have been recorded”.	Hocking et al (1998) p. 81	H
Propagule longevity?	“Seeds, remain dormant in the soil for at least 20 years”.	Muyt (2001) p. 175	H
Reproductive period?	“Plants are believed to live for about 10 to 15 years”. If lived for 15 years would produce seeds for > 10 years.	P & C (1992) p. 470	H
Time to reproductive maturity?	“Plants do not flower until at least 2 years old”.	P & C (1992) p. 470	ML
Dispersal
Number of mechanisms?	See below for comment: also spread by machinery, animals, agricultural products and mud.	P & C (1992) p. 471	MH
How far do they disperse?	“Pods: open during summer, bursting open on hot days to eject the seeds several metres”. “Earthmoving equipment, including road graders are responsible for much spread”.	P & C (1992) p. 470 P & C (1992) p. 471	MH

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