Invasiveness Assessment - Spear thistle (Cirsium vulgare) 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 Spear thistle.

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: Spear thistle
Scientific name: Cirsium vulgare

Question	Comments	Reference	Rating
Establishment
Germination requirements?	Seeds mainly germinate after autumn rains but a few shoot at other times when adequate moisture is available. “Although seeds can germinate at any time of year, there are two main germination times in late summer to autumn and late winter to spring”. (Bruzzese 1996).	P & C (1992) Bruzzese (1996)	H
Establishment requirements?	Mostly occurs in ‘open’ areas/habitats, such as pastures, fields, etc. Also stated that ‘shade’ is known to inhibit C. Vulgare. Occurs in forest woodland. Carr et al (1992).	P & C (1992) USGS Web Page	MH
How much disturbance is required?	Occurs in minor disturbed ecosystems (e.g. wetlands, riparian areas), and highly disturbed areas (e.g. pastures, cultivated fields, waste places). However, mostly occurs in highly disturbed areas.	Carr et al (1992) Felfoldi	MH
Growth/Competitive
Life form?	Erect annual or biennial herb. Geophyte – fleshy storage, roots that can produce new aerial growth.	P & C (1992)	ML
Allelopathic properties?	None described.		L
Tolerates herb pressure?	Not readily grazed by stock.	P & C (1992)	MH
Normal growth rate?	Competes with cereal crops.	P & C (1992)	MH
Stress tolerance to frost, drought, w/logg, sal. etc?	Tolerance to water logging assumed as occurs in riverine habitats (e.g. dam margins, riverbanks, wetlands). Occurs in locations where frosts would occur – Tasmania, Alaska, Canada and others.	Henderson (1995) Carr et al (1992)	MH
Reproduction
Reproductive system	Reproducing by seed: capable of both self-pollination and cross-pollination.	P & C (1992) USGS Web page	ML
Number of propagules produced?	Up to 200 flower heads and 8 000 seeds have been counted on individual plants.	P & C (1992)	H
Propagule longevity?	A Canadian study shows some seed remaining viable for about 36 years.	P & C (1992)	MH
Reproductive period?	Annual or biennial.	P & C (1992)	ML
Time to reproductive maturity?	A flowering stem is produced in late spring of the 2nd year. Biennials. Annuals – first year.	P & C (1992)	H
Dispersal
Number of mechanisms?	Wind, water, vehicles, machinery, animals, mud, pasture seed, contaminated hay.	P & C (1992)	MH
How far do they disperse?	“Most of the seeds land within a few metres of the parent plant and only about 10% are dispersed out of the local population”.	Klinkhamer et al (1988)	MH

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