Invasiveness Assessment - Vasey grass (Paspalum urvillei) 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 Vasey grass.
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: Vasey grass
Scientific name: Paspalum urvillei
| Question | Comments | Rating | Confidence |
| Establishment | |||
| Germination requirements? | Sown in Summer. Storage improves germination as there is “some dormancy” post-harvest and seed ripens unevenly (Speedy 2004). Dormancy was overcome experimentally by manipulating light or temperature and by soil burial in combination with optimal germination temperatures, between 20oC and 30oC (Ishimine 1987). Requires natural seasonal disturbance. | MH | MH |
| Establishment requirements? | “Prefers full sunlight. Does not grow well in shade” (Speedy 2004), however, studies have found that shade enhances the growth of this weed (Ishimine et al. 1985). Likely to be able to establish under moderate canopy cover. | MH | M |
| How much disturbance is required? | Weed of disturbed areas (PIER 2007). Found on a grassy track, amongst other grasses (Moore & Edgar 2007). Establishes in highly disturbed natural ecosystems. | ML | MH |
| Growth/Competitive | |||
| Life form? | Perennial grass (Clayton et al. 2007) with leaves to 60 cm and flowers to 180 cm (Walsh & Entwisle 1994) with short rhizomes 1-1.5 cm diameter (Moore & Edgar 2007). | MH | MH |
| Allelopathic properties? | Exudates significantly reduced the growth of other plants (Ishimine et al. 1987). | MH | MH |
| Tolerates herb pressure? | A study of rice stink bug found that the flowers of this species was preferred, over 11 other grass species, and one sedge (Naresh & Smith 1983). “Killed by heavy grazing [however] not as palatable as other species, quickly becoming coarse and thus avoided by stock” (Speedy 2004). Mature grass not preferred. | MH | MH |
| Normal growth rate? | “Spreads fairly quickly under…moist soil conditions” and has very vigorous seedlings. Competes successfully with weeds (Speedy 2004). Up to 60 days from germination, Paspalum was shorter than sugarcane, but after 120 days it had grown taller than the crop (Ishimine 1987), however examination of the data suggests that when measurements began, the cane was 50 cm tall whilst the weed had just germinated. Able to out compete similar life forms. | H | MH |
| Stress tolerance to frost, drought, w/logg, sal. etc? | Grows from 0-1,000 m in summer-dominant high rainfall regions of 1,000-1,500 mm and can withstand fire, severe drought and a wide range of soils, including very wet land, but does not survive winter in Washington State USA. Tolerance to salinity not recorded (Speedy 2004). Wetland plants (Beadle et al. 2004). Highly tolerant of drought and waterlogging, some tolerance to fire, not highly tolerant of frost. | MH | M |
| Reproduction | |||
| Reproductive system | Sexual (Speedy 2004). Not known if self or cross-fertile. | ML | M |
| Number of propagules produced? | “Heavy seed production” (Speedy 2004). Produces more viable seed than P. dilatatum (Schrauf et al. 2003). P. dilatatum can produce more than 25,000 seeds annually (Muyt 2001). More than 25, 000 seeds produced per plant. | H | MH |
| Propagule longevity? | Seeds survived at least 9 months under various experimental conditions (Ishimine 1987). Unknown beyond this. | M | L |
| Reproductive period? | Abundant seed set in the second or third year of sowing (Rosengurtt 1948). Plants survived a four year study (Schrauf et al. 2003). Mature plant produces viable propagules for at least 3 years, but unlikely to be more than 10 years, as this is a grass. | MH | MH |
| Time to reproductive maturity? | Abundant seed set in the second or third year of sowing (Rosengurtt 1948). 1-2 years to reach sexual maturity. | MH | MH |
| Dispersal | |||
| Number of mechanisms? | Seed is fluffy and smaller than P. dilatatum (Speedy 2004). For P. dilatatum, seed is spread by animals, water, vehicles, machinery, on clothing and footwear (Muyt 2001). This is likely to be true for P. urvillei also. | MH | M |
| How far do they disperse? | Likely to have been introduced to Victoria with stock or grain from interstate (Walsh & Entwisle 1994). Proven ability to disperse greater than one kilometre. | H | MH |
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