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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? | “Growth (vegetative) starts with development of node buds on old stems in early spring”. | P & C (1992) | MH |
Establishment requirements? | “Establishes readily wherever there is an adequate water supply…it has a low light requirement”. | P & C (1992) | H |
How much disturbance is required? | Established in rice crops and inundated pastures. | P & C (1992) | MH |
Growth/Competitive | |||
Life form? | Aquatic (emergent or free flowing) as well as terrestrial. | P & C (1992) | H |
Allelopathic properties? | None described. | L | |
Tolerates herb pressure? | M | ||
Normal growth rate? | “Strong competition in rice fields and pastures prone to water logging, often crowding out desirable species”. “Alternanthera philoxeroides competes successfully with other plants with the exception of water hyacinth. (Spenser & Coulson 1976); (Coulson 1977); (Julien & Broadbent 1980 p. 154). | P & C (1992) | H |
Stress tolerance to frost, drought, w/logg, sal. etc? | Tolerant of frosts, water logging and salinity. “It requires a warm growing season but will tolerate cold winters including severe frosts which may kill emergent stem material. (Coulson 1977)”. (Julien & Broadbent 1980 p. 152). | P & C (1992) | MH |
Reproduction | |||
Reproductive system | “Reproduction in the field is entirely vegetative”. | P & C (1992) | MH |
Number of propagules produced? | “Reproduction in the field is entirely vegetative”. | L | |
Propagule longevity? | L | ||
Reproductive period? | Produces thick mats. (See picture P & C 1992 p. 157). “Floating mats of alligator weed are generally monocultures”. (Julien & Broadbent 1980 p. 152). | P & C (1992) | H |
Time to reproductive maturity? | Nodes on old stems in early spring stems and flowers in mid summer - flowering until March. Some seeds produced but rarely ever viable in Australia. | P & C (1992) | H |
Dispersal | |||
Number of mechanisms? | Water currents and cultivation. | P & C (1992) | MH |
How far do they disperse? | M |