Invasiveness Assessment - Artichoke thistle (Cynara cardunculus) 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 Artichoke 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 - 1026 KB)
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Common Name: Artichoke thistle
Scientific name: Cynara cardunculus

Question	Comments	Reference	Rating
Establishment
Germination requirements?	“Seeds may germinate at any time of the year but most do so after autumn rain”.	P & C (1992)	H
Establishment requirements?	Requires ‘open’ areas e.g. pasture, gardens, wasteland, roadsides, vacant allotments.	P & C (1992) K & J (1997)	ML
How much disturbance is required?	Establishes in minor disturbed ecosystems (e.g. riparian, grassland) and well-established pastures.	P & C (1992) Carr et al (1992)	MH
Growth/Competitive
Life form?	Perennial herb. Other.	P & C (1992) Carr et al (1992)	L
Allelopathic properties?	None described.		L
Tolerates herb pressure?	“The spiny nature of the plant deters sheep and cattle from grazing on heavy infestations but, when hungry, animals will eat the leaves”.	P & C (1992)	MH
Normal growth rate?	Can choke out or dominate vegetation of an area once established.	NSW Dept. Ag (1962) P & C (1992)	MH
Stress tolerance to frost, drought, w/logg, sal. etc?	Tolerance to salinity, presumably also drought (occurs in Ciza & Kalubia, Egypt & Australia). Water logging (occurs in irrigated and riparian areas) ? (Wernli & Tames 1984)	Giushniani et al (1999) Carr et al (1992)	MH
Reproduction
Reproductive system	Reproducing from a perennial taproot and by seed.	P & C (1992)	H
Number of propagules produced?	Approximately 16 inflorescence per plant x 100 florets per inflorescence x 1 seed per floret = approximately 1,600 seeds. About 16 heads on each plant but occasionally > 50 or more inflorescence 8 less florets	P & C (1992)	MH
Propagule longevity?	?		M
Reproductive period?	“Individual plants may live for many years”. Also, can form monocultures. (See pic. P & C 1992 p. 214). Carr et al (1992) also states that the plant forms ‘medium to large infestations’.	P & C (1992)	H
Time to reproductive maturity?	“Plants may flower in the first year but generally flowering is delayed until the second summer”.	P & C (1992)	H
Dispersal
Number of mechanisms?	Mostly seed dispersal – wind, animals, water, mud and birds.	P & C (1992)	H
How far do they disperse?	Seeds are usually blown within a few metres of the birds, plants. Animals, particularly birds and water are however likely to spread seeds farther. Small birds feed on seeds, perhaps dispersing seed > 200 m.	P & C (1992)	H

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