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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? | Late summer to mid winter depending on rainfall. | P & C 1988 | MH |
Establishment requirements? | Cold hardy: tolerant of arid soils. Found in partly drained heavy soils of pasture and stream banks. | MH/ML? | |
How much disturbance is required? | Tolerant of wet soils. Pest of cereals. Waste spaces and roadsides. | DEL & S – Folder | MH/ML |
Growth/Competitive | |||
Life form? | Erect perennial herb. Liliaceace. Geophyte, aerial growth dies in summer. | P & C (1987) | ML |
Allelopathic properties? | L | ||
Tolerates herb pressure? | Heavy grazing prevents the formation of bulbils. Reduced the number and size of bulbs produced. | MH | |
Normal growth rate? | Not generally considered to be a strongly competitive plant. | Building & Control of Wild Dept. CL & S - Folder | ML |
Stress tolerance to frost, drought, w/logg, sal. etc? | Temperate to frost and salinity, drought: (pods die off in sun), water logging: (occurs in stream banks). | MH | |
Reproduction | |||
Reproductive system | Seeds, bulbs and bulbis. | P & C (1987) | H |
Number of propagules produced? | 50-100 per metre square. Bulb and # 15,600 – 13,500 per metre square. | MH/ML | |
Propagule longevity? | Bulbs maybe dormant for up to 6 years. All others either grow or die. | P & C (1987) | L |
Reproductive period? | Perennial. | MH | |
Time to reproductive maturity? | Even bulbis and seeds produce bulbs in first year but flower in second. | H/MH | |
Dispersal | |||
Number of mechanisms? | Seeds, bulbs and bulbis spread by movement of agricultural produce, vehicles, animals, mud and water. Animals can spread seed in faeces – water can carry seeds and bulbs. | P & C (1988) | MH |
How far do they disperse? | 1 km. | H |