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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 in autumn. | P & C (1992) | MH |
Establishment requirements? | Establishes in ‘open’ habitats (e.g. roadsides, fields and gardens). | P & C (1992) Tutin et al (91964) | ML |
How much disturbance is required? | Establishes in vigorously growing crops (e.g. carrots) and pastures. | P & C (1992) | MH |
Growth/Competitive | |||
Life form? | Erect annual or biennial herb. Other. | P & C (1992) | L |
Allelopathic properties? | None described. | L | |
Tolerates herb pressure? | Is grazed but assumed to recover quickly as “slashing or mowing…removes the top growth but stimulates new flowering stems from basal buds”. | P & C (1992) | MH |
Normal growth rate? | “Once established (it) competes with pastures and crops but is rarely considered an important weed”. | P & C (1992) | MH |
Stress tolerance to frost, drought, w/logg, sal. etc? | Assumed tolerant of frost (occurs in southern Tasmania and Great Britain and Ireland), drought (occurs in arid areas of Australia and New South Wales and Western Australia). | P & C (1992) | ML |
Reproduction | |||
Reproductive system | Reproducing by seed. | P & C (1992) | ML/ |
Number of propagules produced? | 15 spike like clusters per plant x 70 flowers per cluster x 2 seeds per flower = 2,000 seeds per plant. (Estimate using illustrations). | P & C (1992) | H |
Propagule longevity? | “Seeds of Resed aceae do not remain viable for more than 3-4 years and there is no evidence for seed longevity > 4 years in this family”. | Heaps et al (1995) | L |
Reproductive period? | Annual/biennial one year. | P & C (1992) | ML |
Time to reproductive maturity? | Annual/biennial one year. | P & C (1992) | H |
Dispersal | |||
Number of mechanisms? | Seeds contaminate agricultural produce, vehicles, machinery, animals, fodder, mud, etc, but, most spread in water and road making materials. | P & C (1992) | MH |
How far do they disperse? | Seeds small (1 mm diameter) therefore could be transported > 200 m. | MH |