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Invasiveness Assessment - Saffron thistle (Carthamus lanatus) 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 Saffron 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)
To view the information PDF requires the use of a PDF reader. This can be installed for free from the Adobe website (external link).

Common Name: Saffron thistle
Scientific name: Carthamus lanatus

Question
Comments
Reference
Rating
Establishment
Germination requirements?Seeds germinate in autumn & early winter.
P&C (2001)
MH
Establishment requirements?Occurs in mostly ‘open’ areas e.g. paddocks, grasslands.
P&C (2001)
Carr et al (1992)
ML
How much disturbance is required?Weed in cultivated paddocks.

Invades lowland grassland & grassy woodland.
P&C (2001)
Carr et al (1992)
MH
Growth/Competitive
Life form?Annual herb → Other.
P&C (2001)
L
Allelopathic properties?Allelopathic properties not described.
L
Tolerates herb pressure?Has little fodder value although it is eaten to some extent when very young and later as the stem emerges from the rosette.
P&C (2001)
MH
Normal growth rate?In crops, competition reduces yield…does not invade perennial pastures nor does it withstand competition from improved annual pastures.
P&C (2001)
MH
Stress tolerance to frost, drought, w/logg, sal. etc?Tolerance to frost & drought (See Australian distribution).
P&C (2001)
M
Reproduction
Reproductive systemReproducing by seed.
P&C (2001)
ML
Number of propagules produced?Individual seed heads can produce 10-16 seeds.

8 seed heads/plant x 16 seeds/head = 128 seeds/plant.
Groves et al (1995)
ML
Propagule longevity?Some survived for up to 8 years but most seemed to be destroyed by bacteria, fungi or termites.
P&C (2001)
L
Reproductive period?Annual her. Forms dense infestations (see pick p196) yet doesn’t appear to be a monoculture.
P&C (2001)
L
Time to reproductive maturity?Annual herb.
P&C (2001)
H
Dispersal
Number of mechanisms?Seed spread by clothing, bags, wool, fur, mud stuck to implements & vehicles, ‘tumbleweed’ effect & the flow of water along channels.
P&C (2001)
MH
How far do they disperse?The dried seed heads tangle in wool & the whole plant breaking off at the base, acts as a ‘tumbleweed’ spreading the seed over long distances.
P&C (2001)
MH


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