Invasiveness Assessment - St. Peter's wort (Hypericum tetrapterum) 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 St Peter's wort.
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 - 1026 KB)
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Common Name: St. Peter’s wort
Scientific name: Hypericum tetrapterum
| Question | Comments | Reference | Rating |
| Establishment | |||
| Germination requirements? | “Seeds germinate in autumn, winter or spring”. | P & C (2001) | MH |
| Establishment requirements? | Appears to occur in ‘open’ situations See pics. In P & C (2001) p. 393 & 394 |  | ML |
| How much disturbance is required? | Occurs in minor disturbed natural ecosystems e.g. riparian. | Carr et al (1992) | MH |
| Growth/Competitive | |||
| Life form? | Herb. Other. | Carr et al (1992) | L |
| Allelopathic properties? | No Allelopathic properties described. | | L |
| Tolerates herb pressure? | “St. Peter’s Wort is believed to be poisonous to stock and to cause photosensitisation”. Consumed, but as H. perforatum probably not preferred. | P & C (2001) | MH |
| Normal growth rate? | The weed forms very dense strands and appears to be as strongly competitive as St. John’s Wort”. | P & C (2001) | H |
| Stress tolerance to frost, drought, w/logg, sal. etc? | Tolerant of water logging (occurs in swampy areas). Frost and drought tolerant. (See European distribution). | P & C (2001) | MH |
| Reproduction | |||
| Reproductive system | “Reproducing by seed and from crowns and stems which produce roots at the lower nodes”. | P & C (2001) | H |
| Number of propagules produced? | Herb to 1 m high: flowers in clusters: fruit many seeded: seeds small. 50 fruits per plant x 20 seed per fruit = 1,000+. | P & C (2001) | MH |
| Propagule longevity? | ? | | M |
| Reproductive period? | “Forms a thick mat smothering other vegetation”. As per H. androsaemum and H. perforatum. | P & C (2001) | H |
| Time to reproductive maturity? | “Generally plants do not flower in the first year”. | P & C (2001) | MH |
| Dispersal | |||
| Number of mechanisms? | “Most dispersal has been by the movement of seeds which float on water and may contaminate soil, mud, agricultural produce, vehicles, animals etc.”. | P & C (2001) | MH |
| How far do they disperse? | | | MH |
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