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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 | Rating | Confidence |
Establishment | |||
Germination requirements? | Seeds germinate with rains at any time of year (CABI 2005). Opportunistic germinator. | H | MH |
Establishment requirements? | Requires light to establish and grow, very sensitive to shade (CABI 2005). | ML | MH |
How much disturbance is required? | Common on riverbanks and watersheds (CABI 2005). Likes open woodlands and grasslands with a tendency to invade degraded areas such as overgrazed grassland. Can establish in relatively intact ecosystems (CRC for Australian Weed Management 2003). | MH | MH |
Growth/Competitive | |||
Life form? | Leguminous, perennial non-climbing tree (CABI 2005). | MH | MH |
Allelopathic properties? | None described in CABI (2005). | L | MH |
Tolerates herb pressure? | A common fodder species browsed by wild and domesticated animals in its native range. Over thirty beetle species have been identified with eight linked to defoliation of trees (CABI 2005). Weed still persists. | ML | MH |
Normal growth rate? | Relatively ‘slow-growing’ tree in natural environments (CRC for Australian Weed Management 2003). | L | M |
Stress tolerance to frost, drought, w/logg, sal. etc? | Can tolerate frost (to -1°C), saline soil tolerant, tolerant of fire and drought. Seeds susceptible to waterlogging (CABI 2005). | MH | MH |
Reproduction | |||
Reproductive system | Reproduces by seed only. No information on whether self and /or cross- pollination occurs so scores as ML (CABI 2005). | ML | MH |
Number of propagules produced? | Seedpods contain between four and seven seeds. Mature trees produce ‘large numbers’ of seeds. Assume greater than 2000 propagules produced per flowering event (CRC for Australian Weed Management 2003). | H | M |
Propagule longevity? | Exact length not known but ‘probable that some seeds remain viable for about 20 years’ (CRC for Australian Weed management 2003). | ML | M |
Reproductive period? | Not specified although in areas where grown for forestry rotated every 20 years. Trees live up to 60 years. Score High as likely that produces viable propagules for greater than 10 years and records of the tree forming monocultures in some areas in Asia (CABI 2005). | H | MH |
Time to reproductive maturity? | Life cycle under Australian conditions is unknown and time to reproductive maturity is unclear (Parsons & Cuthbertson 2001). Therefore score as medium. | M | MH |
Dispersal | |||
Number of mechanisms? | Transported by cattle, water, humans, machinery movement (CABI 2005). | MH | MH |
How far do they disperse? | Can be transported long distances by cattle therefore likely that some propagules will spread greater than 1 km (CRC for Australian Weed management 2003). | H | M |