Invasiveness Assessment - Marijuana (Cannabis sativa) in Victoria
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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. |
The following table provides information on the invasiveness of Marijuana.
A more detailed description of the methodology of the Victorian Weed Risk Assessment (WRA) method can be viewed below:
Victorian Weed Risk Assessment (WRA) method (PDF - 630 KB)
Victorian Weed Risk Assessment (WRA) method (DOC - 1 MB)
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Common Name: Marijuana
Scientific name: Cannabis sativa
| Question | Comments | Reference | Rating |
| Establishment | |||
| Germination requirements? | “Seeds germinate from mid-spring to early autumn.” Requires natural seasonal disturbance (i.e. temperature & rainfall). | Parsons & Cuthbertson (2001) | MH |
| Establishment requirements? | A sun-loving plant, occurring on well drained fertile soils, commonly along streams, roadsides, fence lines and neglected fields. Requires open situation and fertile soils. | Parsons & Cuthbertson (2001) | ML |
| How much disturbance is required? | Occurs in disturbed situations such as stream banks, roadsides, fence lines and neglected pastures. | Parsons & Cuthbertson (2001) | ML |
| Growth/Competitive | |||
| Life form? | Annual herb. Others. | Parsons & Cuthbertson (2001) | L |
| Allelopathic properties? | None reported. |  | L |
| Tolerates herb pressure? | No data available. The plant has poisoned horses and mules in Greece; cattle and sheep may avoid it. | Parsons & Cuthbertson (2001) | MH |
| Normal growth rate? | “Hemp grows rapidly and soon crowds out weeds. Hemp tends to exhaust the soil of nutrients.” “It is not usually competitive with crops but, in India, sometimes significantly reduces maize yields.” Possibly exceeds growth rate of species of similar life form. | Duke (1983) Parsons & Cuthbertson (2001) | MH |
| Stress tolerance to frost, drought, w/logg, sal. etc? | “… plants are killed by frost. “ As the root system comprises a much-branched taproot with a mass of laterals in the upper 20 cm of soil, it would possibly survive dry periods during summer. “… once established, [it] survives on very little water.” | Parsons & Cuthbertson (2001) | ML |
| Reproduction | |||
| Reproductive system | Reproduces sexually. Dioecious plants; possibly out-cross. | Parsons & Cuthbertson (2001) | L |
| Number of propagules produced? | Plants produce abundant seed! Assume plant produces less than 2,000 seeds. | Parsons & Cuthbertson (2001) | MH |
| Propagule longevity? | “Seed stored in cool dry place remain viable for up to two years.” Seeds survive less than 5 years. | Duke (1983) | L |
| Reproductive period? | An annual. Mature plant produces propagules for only one year. | Parsons & Cuthbertson (2001) | L |
| Time to reproductive maturity? | “Plants germinate from mid-spring to early summer and the plant requires about 110 days to mature. Flowering begins in January and continues until late autumn.” Reaches maturity in less than one year. | Parsons & Cuthbertson (2001) | H |
| Dispersal | |||
| Number of mechanisms? | The seed is not equipped with any mechanism to aid dispersal. Most seeds fall close to the plant. Seed can be spread by water, and some by birds. However, the majority of spread is by deliberate human action. Spread by highly mobile animals. | Parsons & Cuthbertson (2001) | H |
| How far do they disperse? | Some seed may be dispersed less than 1 km due to water or birds but, as most spread is due to human agency, propagules may spread more than one kilometre. | Parsons & Cuthbertson (2001) | H |
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