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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 and corms germinate after autumn rains”. | P & C (1992 p. 75) | MH |
Establishment requirements? | “It does not establish well on shaded sites: but establishes. Invades dry sclerophyll forest and woodland where some shading would occur. | P & C (1992 p. 74) Carr et al (1992) | MH |
How much disturbance is required? | Occurs in heathland and heathy woodland. | Carr et al (1992) | H |
Growth/Competitive | |||
Life form? | Cormour geophyte. | Carr et al (1992) | ML |
Allelopathic properties? | No allelopathic properties described. | ML | |
Tolerates herb pressure? | “Stock accustomed to grazing on infested areas are seldom affected, mainly because they do not eat much of the plant”. | P & C (1992 p. 76) | MH |
Normal growth rate? | “Patches can be very dense with almost 7,000 corms per square metre recorded in some areas”. See pic. in P & C (1992 p. 76). | P & C (1992) Carr et al (1992) | MH |
Stress tolerance to frost, drought, w/logg, sal. etc? | Occurs in semi arid areas. Some corms likely to survive fire. Occurs in freshwater wetland (seasonal). | P & C (1992 p. 74) Carr et al (1992) | MH |
Reproduction | |||
Reproductive system | “Reproducing from corms and by seed”. | P & C (1992 p. 75) | H |
Number of propagules produced? | Up to 150 seeds per capsule x 8 capsules per plant = 1,200 seeds. (See description and illustration in P & C (1992 p. 75)). | P & C (1992 p. 75) | MH |
Propagule longevity? | “Seeds are not long lived in the soil and most germinate in the autumn following formation. Corms show longer viability than seeds”. | P & C (1992 p. 76) | L |
Reproductive period? | Competes with crops and pastures and a very serious threat to indigenous communities. | P & C (1992 p. 76) | H |
Time to reproductive maturity? | “Plants are 2 or 3 years old before they flower and produce seeds”. | P & C (1992 p. 75) | ML |
Dispersal | |||
Number of mechanisms? | Machinery, animals (internal and external), wind and water. | P & C (1992 p. 76) | MH |
How far do they disperse? | “Seeds remain viable after passing through stock and spread throughout much of WA, is thought to have been in cattle droppings. | P & C (1992 p. 76) | H |
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