Invasiveness Assessment - Drooping prickly pear (Opuntia vulgaris) in Victoria (Nox)
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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 Drooping prickly pear.
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: Prickly pear, drooping
Scientific name: Opuntia vulgaris
| Question | Comments | Reference | Rating |
| Establishment | |||
| Germination requirements? | Germination as for wheel cactus (O. robusta). “Seeds germinate at any time of the year.” | P & C (1992 p. 363) | H |
| Establishment requirements? | In Victoria, it occurs on lowland grassland & grassy woodland and rock outcrop situations. As with wheel cactus, seedlings are very delicate and usually do not survive in exposed situations. Seedling survival may depend on suitable cover/shelter. | Carr et al (1992) Parsons & Cuthbertson (2001) | ML |
| How much disturbance is required? | It is known to occur in lowland grassland and grassy woodland environments. Flora of Australia states the species occurs in open forest, woodland and pasture. Able to establish in relatively undisturbed natural ecosystems. | Carr et al (1992) FoA (1984) | MH |
| Growth/Competitive | |||
| Life form? | Erect succulent shrub. Other. | Parsons & Cuthbertson (2001) | L |
| Allelopathic properties? | None documented. |  | L |
| Tolerates herb pressure? | Opuntia species are not usually grazed by stock because of the stout spines and bristles. Birds, foxes and other animals eat the fruits, but seeds remain viable after passing through the animal. Consumed but recover quickly. Seeds remain viable after consumption. | Parsons & Cuthbertson (2001) | MH |
| Normal growth rate? | From seedling stage, growth is slow. Growth rate, however, is probably equal to species of same life form. | Parsons & Cuthbertson (2001) | MH |
| Stress tolerance to frost, drought, w/logg, sal. etc? | Drought tolerant. Information regarding tolerance to frost, waterlogging, salt and fire is lacking. | Parsons & Cuthbertson (2001) | ML |
| Reproduction | |||
| Reproductive system | Reproduces from seed and segments (sexually and vegetatively). | Parsons & Cuthbertson (2001) | H |
| Number of propagules produced? | From photo (p 367) in Parsons & Cuthbertson (2001), it appears the plant produces more than 100 flowers per season. Flowers contain between 8 and 20 seeds. Seed quantity may exceed 2,000 per plant. | Parsons & Cuthbertson (2001) Light (1884) | H |
| Propagule longevity? | Seed longevity is not documented. However, segments from which new plants can arise (the areoles in contact with the soil produce roots, while those on the upper surface produce new segments, P&C (2001) p 363) have been known to survive indoors for 3 years. | Parsons & Cuthbertson (2001) p361 | L |
| Reproductive period? | Plants are long lived. Assume more than 10 years. | Parsons & Cuthbertson (2001) | H |
| Time to reproductive maturity? | As for wheel cactus (O. robusta). The first flowers do not develop until plants are at least 3 years old. | Parsons & Cuthbertson (2001) | ML |
| Dispersal | |||
| Number of mechanisms? | As for tiger pear (O. aurantiaca). “Segments or fruit drop to the ground and take root. Detached segments, as well as fruit, are carried by flood waters.” “…prickly pear produces viable seed which is spread in the droppings of birds, foxes and other animals.” Spread by water and animals. | Parsons & Cuthbertson (2001) | MH |
| How far do they disperse? | Seed spread by animals may disperse plants beyond one kilometre. Spread due to fallen segments and fruit limited to within parent plant. | Parsons & Cuthbertson (2001) | MH |
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