Invasiveness Assessment - Uruguayan Rice Grass (Piptochaetium montevidense) 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 Uruguayan rice 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: Uruguayan rice grass
Scientific name: Piptochaetium montevidense
| Question | Comments | Rating | Confidence |
| Establishment | |||
| Germination requirements? | This species was successfully germinated in the temperate greenhouse at the Botanic Garden of the Institute of Botany in Graz (Austria, Europe), giving a “vague” impression of the conditions under which it was grown (Teppner, 2002). Not enough information was found to indicate germination requirements. | M | L |
| Establishment requirements? | Observed as a dominant understorey species below Serrated tussock and Chilean needle grass in Argentina (David Maclaren, pers. comm.). Can establish under moderate canopy cover. | MH | MH |
| How much disturbance is required? | Disturbed grassland…it can also invade relatively undisturbed vegetation (CRC Weed Management, 2003b). A weed of crops, natural areas, roadsides and urban areas (Cunningham et al, 2003). | MH | M |
| Growth/Competitive | |||
| Life form? | Perennial stipoid grass (Cunningham et al, 1993). | MH | MH |
| Allelopathic properties? | No evidence found. There is little information available about this species, so a medium value was chosen. | M | L |
| Tolerates herb pressure? | Resistant to grazing (CRC Weed Management, 2003a; Cunningham et al, 2003). Recorded as growing in a region of Brazil that has been grazed for the last 30 years by cattle, sheep and occasionally by horses (Maia et al, 2004). Unpalatable (David Maclaren, pers. comm.). | MH | H |
| Normal growth rate? | As an understorey to Nasella spp. in Argentina (David Maclaren, pers. comm.), indicates that it doesn’t grow as vigorously as these grasses, but no further information about its growth rate has been found. | M | L |
| Stress tolerance to frost, drought, w/logg, sal. etc? | Burning stimulates development (Heringer & Jacques, 2002). Maia et al (2004) found this plant associated with less wet habitats and uplands and intermediate sites. Focht & Pillar (2003) found the plant growing mainly in the dryer slopes (moist only after rain) of a Brazilian grassland site, but it still appeared in almost 40% of the wet lowland areas that were almost always moist (although at half the abundance of the drier sites). This is a major species from the Salado River Basin, an area that is subject to frequent flooding and severe summer droughts (Sala et al, 1981). In Victoria it was growing at Cherry Lake, near Altona (Cunningham et al, 1993), a site that is 400 m from the saline Port Phillip Bay. A specimen of this plant was collected from 3,400 m up Chimborazo in Ecuador (Anon, 2005) at elevations that reach freezing in the Andes (Neill, 1999). The types of environments in which it is found suggests that P. montevidense is tolerant of drought, frost, salinity and waterlogging, and it appears to be tolerant of fire. It may not be susceptible to any of these stressors. | MH | H |
| Reproduction | |||
| Reproductive system | Plants are bisexual with bisexual spikelets and hermaphrodite florets (Cunningham et al, 2003). No evidence of vegetative reproduction was found. | M | L |
| Number of propagules produced? | Produces many seeds. Although the exact volume or seed produced is unknown (CRC Weed Management, 2003a). | M | L |
| Propagule longevity? | No information found. | M | L |
| Reproductive period? | Dense sward (Cunningham et al, 2003), but this is not necessarily a monoculture. No further information was found. | M | L |
| Time to reproductive maturity? | Germinates Spring and Autumn, flowers Sept-Dec, seeds form in Dec & dropped by early Autumn (CRC Weed Management, 2003b). Reaches reproductive maturity in under one year. | H | M |
| Dispersal | |||
| Number of mechanisms? | Dispersed by wind and also by browsing animals ingesting the plant and excreting the viable seed elsewhere…anectodal evidence suggests that seeds are not carried or dispersed externally by stock (CRC Weed Management, 2003b). | MH | MH |
| How far do they disperse? | Animals digesting the seed have the potential to transport them several kilometres. | H | MH |
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