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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. |
Question | Comments | Reference | Rating |
Establishment | |||
Germination requirements? | Seeds germinate at any time of the year. | H | |
Establishment requirements? | Occurs in open areas. | P & C (2001) | ML |
How much disturbance is required? | Establishes in pastures. Listed as a ‘problematic weed of agricultural situations’. | P & C (2001) Scott & Delfosse (1992) | MH |
Growth/Competitive | |||
Life form? | Large shrub. | L | |
Allelopathic properties? | No allelopathic properties described. | L | |
Tolerates herb pressure? | Seldom grazed by stock because of the sharp spines. | P & C (2001) | MH |
Normal growth rate? | Early root growth is rapid ensuring young plants are competitive. | P & C (2001) | H |
Stress tolerance to frost, drought, w/logg, sal. etc? | Tolerant of drought and frost (refer to Australian Distribution). Some water logging (occurs in creek beds and along streams and rivers). | P & C (2001) | MH |
Reproduction | |||
Reproductive system | Reproducing by seed. | P & C (2001) | ML |
Number of propagules produced? | Fruit production has ranged between 0 & 535. Seeds numerous. ˜ 500 fruit x 10 seeds per fruit = 5,000 seeds. | Erkelenz & Carter (1994) | H |
Propagule longevity? | ? | M | |
Reproductive period? | Large shrub. Produces dense thickets. | P & C (2001) | H |
Time to reproductive maturity? | Plants do not flower until at least 2 years old. | P & C (2001) | MH |
Dispersal | |||
Number of mechanisms? | The fruit is commonly eaten by birds and foxes and the seeds are viable when excreted. | P & C (2001) | H |
How far do they disperse? | Above animals could disperse seeds > 1 km as quite mobile. | H |