Invasiveness Assessment - Divided sedge (Carex divisa) 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 Divided sedge.
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: Divided sedge
Scientific name: Carex divisa
| Question | Comments | Rating | Confidence |
| Establishment | |||
| Germination requirements? | No information on the germination requirements of Carex divisa was found documented. | M | L |
| Establishment requirements? | It is recorded as inhabiting creekline grassy woodland and herb-rich woodland communities, (pers.com.) an indication that it may be able to establish under a moderate canopy cover. | MH | ML |
| How much disturbance is required? | Naturalised along creek flats in Victoria (Walsh & Entwisle 1994) and documented as invading grassland, (Richardson et al 2006, K. Roberg pers.com.) and riparian and creek line grassy woodland (I. Higgins pers.com.). Establishes in minor disturbed natural ecosystems e.g. grassland, riparian vegetation. | MH | M |
| Growth/Competitive | |||
| Life form? | Tufted sedge to 80 cm with long creeping rhizomes (Richardson et al 2006; Walsh & Entwisle 1994, eflora 2007). Lifeform: geophyte. | ML | MH |
| Allelopathic properties? | No information was found documented to indicate C. divisa possesses any allelopathic properties, however, literature on this species is limited. | M | L |
| Tolerates herb pressure? | There is information from France indicating that C. divisa is a species of grasslands and is grazed by sheep (Aich, O’Rourke & Bourbouze 1980). Observations in Victoria indicate it is rarely grazed unless animals are forced through starvation (I. Higgins pers.com.). It appears that this species is consumed, but it is not preferred by grazing animals. | MH | M |
| Normal growth rate? | A rapid rhizome spreading species that can be difficult to control (Walsh & Entwisle 1994). Has rapidly invaded adjacent pasture and grassland areas (Richardson et al 2006). Growth rate in comparison to species of the same life-form was not found documented. | M | L |
| Stress tolerance to frost, drought, w/logg, sal. etc? | ‘The frequent flooding of permanent pastures in winter, favours the development of Carex divisa…’ (Jeannin & Lafon 1975). Known to occur on coastal marshes (Aich et al 1980), ‘halophytic meadows’ (Vanden Berghan 1965) and often found in brackish situations (Richardson et al 2006). Known to occur in the Atlas mountains with a mean minimum Winter temperature of -2oC and precipitation mostly falling as snow from December to March. Possesses thick, woody rhizomes (Jermy & Tutin 1982). Likely to be tolerant of frost, salt and water logging and the presence of thick rhizomes may indicate some tolerance to fire. | MH | M |
| Reproduction | |||
| Reproductive system | Inflorescence is a spike containing both male and female flowers and the seed is a dark yellow-brown nut (Walsh & Entwisle 1994). Spreads by rhizomes (Walsh & Entwisle 1994). Reproduces both sexually and vegetatively. | H | M |
| Number of propagules produced? | No information was found on the number of propagules produced by C. divisa. | M | L |
| Propagule longevity? | No information was found on the longevity of propagules produced by C. divisa. | M | L |
| Reproductive period? | ‘Theoretically, clones of many [Carex] species may survive for many hundreds of years by growing at one end and dying at the other…’ (Bernard 1990). Examples of documented life-spans of some Carex species include: C. flava more than 10 years, C. comosa, more than 20 years and C. pilosa & C. stricta, more than 50 years. From this information on Carex as a genus, it appears likely that mature C. divisa plants would continue to produce propagules for at least 10 years. It has also been described as being a ‘long lived’ species (I. Higgins pers.com.). | H | ML |
| Time to reproductive maturity? | Described as being able to produce seed ‘by two years post-germination’ (I. Higgins pers.com.). | MH | M |
| Dispersal | |||
| Number of mechanisms? | Introduced for Stream bank stabilisation but has rapidly invaded adjacent pasture and grassland areas (Richardson et al 2006, Walsh & Entwisle 1994). In Victoria recorded growing in riparian situations with spread being via soil movement and probably water flow (I. Higgins pers.com.). Viable seeds of C. divisa have been found in the dung of red deer (Malo & Suarez 1995). Dispersal is most likely by water and soil movement and potentially by animals. | MH | M |
| How far do they disperse? | Although no information was found on the dispersal distance of propagules, through water and potentially animal dispersal, it is possible that propagules could travel at least 200 m. | MH | ML |
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