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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 or spring if sufficient moisture is available”. | P & C (1992 P. 107) | MH |
Establishment requirements? | “Invasive in heathlands, woodlands. Would receive some shading in such ecosystems. | MH | |
How much disturbance is required? | “Invasive in heathlands, woodlands. Would receive some shading in such ecosystems. Forest, grasslands and riverine environments”. | Muyt (2001 p. 70) | H |
Growth/Competitive | |||
Life form? | Perennial grass. | P & C (1992 P. 106) | MH |
Allelopathic properties? | No Allelopathic properties described. | L | |
Tolerates herb pressure? | “Generally considered to be an unpalatable weed although in South Africa, Argentina and the United States some strains are looked on as valuable pasture grasses”. | P & C (1992 P. 107) | MH |
Normal growth rate? | “It is an aggressive, tenacious species capable of dominating the ground flora”. | Muyt (2001 p. 70) | MH |
Stress tolerance to frost, drought, w/logg, sal. etc? | Drought and frost tolerant. Occurs in freshwater wetland (seasonal). | Muyt (2001 p. 70) Carr et al (1992) | MH |
Reproduction | |||
Reproductive system | “Reproducing apomictically (without fertilisation) by seed”. | P & C (1992 P. 106) | ML |
Number of propagules produced? | “Ability to produce copious quantities of seed”. “Plants produce large quantities of seed”. | P & C (1992 P. 108) Muyt (2001 p. 70) | H |
Propagule longevity? | ? | M | |
Reproductive period? | ? Likely produces propagules > 3 years as a perennial spp. | MH | |
Time to reproductive maturity? | Germinates autumn/spring plants re sprout the following spring flowers in early summer. | P & C (1992 P. 107) | MH |
Dispersal | |||
Number of mechanisms? | Wind, animals, humans, vehicles, etc. | P & C (1992 P. 107) | MH |
How far do they disperse? | “One of the most important means of spread is as a contaminant of soils and gravel’s used in road making and during road grading”. | P & C (1992 P. 107) | MH |