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Invasiveness Assessment - Bulbil watsonia (Watsonia meriana) 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 Bulbil watsonia.
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: Bulbil watsonia
Scientific name: Watsonia meriana
*“Watsonia meriana cv bulbillefera is a cormous perennial native to Southern Africa & also known as W. bulbillefera J. Mathews & L. Bolus”. (Wilson & Conran 1993).
| Question | Comments | Reference | Rating |
| Establishment | |||
| Germination requirements? | Corms and cormils germinate in late autumn. | P & C (1992) | MH |
| Establishment requirements? | Mostly occurs in ‘open’ habitats (e.g. pastures, roadsides, neglected areas, grasslands). | P & C (1992) Carr et al (1992) | ML |
| How much disturbance is required? | Establishes in minor disturbed natural ecosystems (e.g. ‘lowland grassland and grassy woodland’), and pasture. Cooke (1998) | P & C (1992) Carr et al (1992) | MH |
| Growth/Competitive | |||
| Life form? | Erect perennial herb, reproducing from corms and cormils geophyte. | P & C (1992) Carr et al (1992) | ML |
| Allelopathic properties? | None described. | L | |
| Tolerates herb pressure? | “Animals do not graze mature plants but young shoots are eaten”. | P & C (1992) | MH |
| Normal growth rate? | “Highly competitive in cleared areas on heavy soil…can build up dense colonies which exclude other species”. | APCC (1992) | MH |
| Stress tolerance to frost, drought, w/logg, sal. etc? | Tolerant of water logging, drought (occurs dry areas of Western Australia), fire (re-grows from underground structures, frost (occurs in Southern Tasmania). | P & C (1992) Blood (1997) | MH |
| Reproduction | |||
| Reproductive system | Reproducing from corms and cormils. Also reproducing from seed. | P & C (1992 RPPSWG (1991) | H |
| Number of propagules produced? | Estimate based on pictures and descriptions: 15 flowers per plant x 10 seeds per flower = 75. | ML | |
| Propagule longevity? | ? | M | |
| Reproductive period? | Aerial growth does annually (in summer), however re grows from corms. Some corms have been observed with 35 plates, indicating the minimum age of some Watsonia ‘stands’. (Wilson & Conran 1993). | P & C (1992 | H |
| Time to reproductive maturity? | Plants developing from cormils do not flower in first year, but in either the second or third year. | P & C (1992 | ML |
| Dispersal | |||
| Number of mechanisms? | Corms and cormils – graders and other earth moving equipment. | P & C (1992 | MH |
| How far do they disperse? | “Seeds and bulbils usually fall to the ground and germinate next to the parent plant, resulting in a slow expansion of an existing infestation”. (RPPSWG 1991). | L | |
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