Invasiveness Assessment - Gazania (Gazania linearis) 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 Gazania.
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: Gazania
Scientific name: Gazania linearis
| Question | Comments | Rating | Confidence |
| Establishment | |||
| Germination requirements? | Gazanias in general germinate or spread vegetatively whenever conditions suit (DeLaine & Stokes, 2006). Grow from seed in March or April (van der Spuy, 1971). Require seasonal temperatures. | MH | MH |
| Establishment requirements? | Grows in full sun to partial shade (Klett, 1999). Whilst many horticultural books state that G. linearis requires full sun, this is likely to refer to its ability to flower, rather than limits to its survival or establishment. “It can tolerate light shade under Coastal Wattle” (Pittwater Council, 2007). Able to establish under moderate canopy cover. | MH | M |
| How much disturbance is required? | Has naturalised in an area of native grassland that was once in good condition, now no longer considered significant due to the Gazania infestation (Faithfull, 2006). Establishes in relatively intact grassland. | MH | MH |
| Growth/Competitive | |||
| Life form? | Clump-forming species recorded as growing in terrestrial environments (Faithfull, 2006). Rhizomatous (Webb et al, 1988). | ML | MH |
| Allelopathic properties? | May have allelopathic properties, as Gazania patches are always bare of other plants (Cordingley & Petherick, 2005). Major allelopathic properties. | H | M |
| Tolerates herb pressure? | No information found. | M | L |
| Normal growth rate? | Spreads slowly (Linsley, 2007). | ML |  |
| Stress tolerance to frost, drought, w/logg, sal. etc? | Tolerates fairly severe frost (van der Spuy, 1971). Grows from sea level to 3,050 m (Hilliard, 1977). Withstands salt-laden winds (Groves et al, 2005). Tolerates some soil dryness, but overly moist soils can lead to root and stem rot (MBG, 2006). Drought tolerant and needs good drainage (Linsley, 2007). Fire resistant (Batten & Bokelmann, 1966). Highly tolerant of frost, salinity and drought; moderately tolerant of fire; not tolerant of waterlogging. | MH | MH |
| Reproduction | |||
| Reproductive system | “Produces abundant wind-blown seeds and spreads rapidly. It also spreads vegetatively…It is often spread in garden waste” (Groves et al, 2005). Can be propagated from stem cuttings (Page & Olds, 1997). Both vegetative and sexual reproduction. | H | MH |
| Number of propagules produced? | Abundant (Faithfull, 2006). No further information found. | M | L |
| Propagule longevity? | Able to reproduce from a seedbank following control efforts (J. Virtue, 2007, pers. Comm., 23rd March). However, it is not known if seeds remain dormant for more than 5 years. | M | L |
| Reproductive period? | | | |
| Time to reproductive maturity? | Gazanias in general grown in a hothouse, are capable of flowering within 4 months (Ball, 1985). Reaches reproductive maturity in less than one year. | H | MH |
| Dispersal | |||
| Number of mechanisms? | “Seeds spread by water and wind” (Blood, 2001). Seeds are carried by water (DeLaine & Stokes, 2006; Carr et al, 1992). | MH | MH |
| How far do they disperse? | Most propagules, spread by water and wind (Blood, 2001), could disperse 20-200 m, with few to none likely to disperse to 1 km. | ML | M |
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