Invasiveness Assessment - Spiny emex (Emex australis) 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 Spiny emex.
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 - 1026 KB)
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Common Name: Spiny emex
Scientific name: Emex australis
| Question | Comments | Reference | Rating |
| Establishment | |||
| Germination requirements? | “Seeds germinate at almost any time of year if soil moisture is adequate”. | P & C (1992) | H |
| Establishment requirements? | Occurs in mostly ‘open habitats’. (See Habitats section). “Grows best in the open rather than in the shade of other plants”. | (Gilbey and Weiss 1980) | ML |
| How much disturbance is required? | Is an envil weed in “lowland grassland and grassy woodland”. Serious weed of crops and pastures. | Carr et al (1992) Weiss & Simmons (1979) | MH |
| Growth/Competitive | |||
| Life form? | A semi prostrate annual herb. Other. | P & C (1992) | L |
| Allelopathic properties? | None described. |  | L |
| Tolerates herb pressure? | Not readily eaten by stock. | P & C (1992) | MH |
| Normal growth rate? | “It competes with cereal crops and pastures because it is fast growing”. | P & C (1992) | MH |
| Stress tolerance to frost, drought, w/logg, sal. etc? | Tolerant of moisture stress. | P & C (1992) Hawkes Bay RC (1995) | L |
| Reproduction | |||
| Reproductive system | Reproducing by seed-male and female flowers separate on the same plant. | P & C (1992) | ML |
| Number of propagules produced? | “Up to 1 100 seeds have been recorded on individual plants”. | P & C (1992) | MH |
| Propagule longevity? | Fruit is long-lived in soil (>4 years). “On undisturbed areas, very little seed germinates after 2 years”. | P & C (1992) | L |
| Reproductive period? | Forms dense monocultures, sometimes > 900 plants per sq. m. | P & C (1992) | H |
| Time to reproductive maturity? | Germination mostly occurs in autumn/winter – flowering late winter/early summer – seed maturation spring and through summer. | P & C (1992) | H |
| Dispersal | |||
| Number of mechanisms? | Fruit (with spines) attach to shoes, rubber tyres, feet of animals or containers of produce. Also contaminated fodder and water. | P & C (1992) | MH |
| How far do they disperse? | Above mechanisms could transport seeds > 200 m. | | MH |
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