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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 early in the wet season, following the first significant storms’ (CRC for Australian Weed Management 2003). Requires seasonal rainfall for germination. | MH | M |
Establishment requirements? | ‘Moderately intolerant of shade, growing in both full sunlight and under light forest canopies’ (Francis 2002). Can establish under a moderate canopy. | MH | MH |
How much disturbance is required? | ‘Most often found on roadsides, bluffs and bars above streams, overgrazed range, disturbed areas, and farmsteads’ (Francis 2002). ‘Grows well in tropical savanna country and along riverbanks’ (CRC for Australian Weed Management 2003). Although common in highly disturbed natural ecosystems, can establish in relatively intact natural ecosystems also. | MH | MH |
Growth/Competitive | |||
Life form? | Perennial shrub (Francis 2002) – other. | L | MH |
Allelopathic properties? | None described in Francis 2002. | L | MH |
Tolerates herb pressure? | ‘Spiny and generally ignored by cattle ’ (Francis 2002). ‘Unpalatable to stock’ (CRC for Australian Weed Management 2003). Favoured by heavy grazing as not eaten by animals / insects. | H | MH |
Normal growth rate? | ‘Dense stands eliminate most other ground vegetation. ..the species doesn’t compete well in dense stands of tall grass. ‘ Seedlings of porcupine flower grow slowly at first’ (Francis 2002). Insufficient information. Score as medium. | M | MH |
Stress tolerance to frost, drought, w/logg, sal. etc? | Grows on sandy soils. Susceptible to frost (CRC for Australian Weed Management 2003). Insufficient information to determine if tolerant of drought, waterlogging and / or fire. Score as medium. | M | M |
Reproduction | |||
Reproductive system | ‘Reproduces by seed.’ ‘Many plants that are closely related to baleria are capable of vegetative reproduction .. baleria can probably also reproduce vegetatively’ (CRC for Australian Weed Management 2003). | H | M |
Number of propagules produced? | ‘Each seed capsule contains two fairly large flat seeds’.’. one plant producing up to hundreds of seeds in a season’ (CRC for Australian Weed Management 2003). | ML | M |
Propagule longevity? | ‘Forty-four percent of the seeds sown on commercial potting mix germinated between 13 and 77 days following sowing ..not known how long the seeds remain viable in the soil after being dropped but it is likely to be at least several years’ (Francis 2002). | L | MH |
Reproductive period? | ‘In Puerto Rico, these shrubs live about 4 years’. ‘Can probably live for about ten years in good conditions’ (CRC for Australian Weed Management 2003). | MH | M |
Time to reproductive maturity? | ‘Not definitively known how old seedlings are before they first flower’. ‘In Katherine plants do not flower until they are at least half a metre tall and their estimated age is one year’ (CRC for Australian Weed Management 2003). | MH | M |
Dispersal | |||
Number of mechanisms? | '.. animal vectors for seed dispersal are lacking’ (Francis 2002). ‘Infestations can move relatively quickly downhill, where seed transport may be aided by water’. ‘.. infestations in Australia have been traced back to escapees from gardens .. from garden waste that was dumped in bushland or transported on heavy machinery’ (CRC for Australian Weed Management 2003). | MH | M |
How far do they disperse? | ‘Natural regeneration generally occurs within 1 or 2 m of the parent plant (Francis 2002). However, attached to machinery or spread along roadways, highly likely that some propagules will disperse greater than 1 km. | H | MH |
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