Invasiveness Assessment - Canary Island St John's wort (Hypericum canariense) 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 Canary Island St John'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: Canary Island St John's wort
Scientific name: Hypericum canariense

Question	Comments	Rating	Confidence
Establishment
Germination requirements?	‘Water is sufficient to break seed dormancy’ (Dlugosch 2004). Opportunistic germinator.	H	MH
Establishment requirements?	‘It seems to invade only disturbed or dry sites that have sufficient light’ (PIER 2005). Requires more specific requirements to establish.	ML	MH
How much disturbance is required?	In Hawaii found ‘along roads, in yards, gulches, and pastures’ (Starr et al 2003). On Canary Islands it is found in dry scrub and laurel forests (Dlugosch 2004). Also found in coastal sage scrub and in grassland habitats (PIER 2005). Can establish in minor disturbed natural ecosystem.	MH	MH
Growth/Competitive
Life form?	Shrub (Randall 2002). Life form – other.	L	H
Allelopathic properties?	None described (PIER 2005).	L	MH
Tolerates herb pressure?	In Maui numerous insects were observed to be associated with H. canariense however ‘none of these insects were doing much damage to the plants’ (Starr et al 2003). Consumed but recovers quickly.	MH	MH
Normal growth rate?	‘Given favourable conditions, it may grow to over 1 m in its first year’ (Dlugosch 2004). In California it does out compete dominant native shrubs (Randall 2002). Rapid growth rate that will exceed most other species of same life form.	H	H
Stress tolerance to frost, drought, w/logg, sal. etc?	Found in xerophytic scrub (PIER 2005). Somewhat tolerant to drought. In its native range in Canary Islands, not subjected to frost. Occurs in places with salinity (Hansford & Laconis 2004). No evidence to suggest that plant is tolerant of fire or waterlogging.	ML	H
Reproduction
Reproductive system	Reproduces by both seeds and rhizomes (Hansford & Laconis 2004). Both vegetative and sexual reproduction.	H	H
Number of propagules produced?	Seeds are numerous (Randall 2002). Each fruit ‘releases hundreds of tiny seeds’ (Dlugosch 2004). Produces greater than 2,000 seeds per flowering event.	H	H
Propagule longevity?	‘.. seed germination rate is approximately 50%’ (Dlugosch 2004). Longevity not documented but no evidence to suggest seed survival is greater than 5 years.	L	MH
Reproductive period?	‘Left undisturbed it is very likely to develop dense monoculture infestations’ (Randall 2002).	H	H
Time to reproductive maturity?	‘Flowers and fruits may be produced in the first year of growth’ (Dlugosch 2004).	H	MH
Dispersal
Number of mechanisms?	‘[H. canariense] light seeds are probably wind dispersed’. Plants are found along roads, which may be an indication that it is spread by light vehicular traffic. (Starr et al 2003).	MH	MH
How far do they disperse?	‘Local spread in California ranges from 45 to 90 metres a year, which is considerable distance for a perennial shrub with no outside assistance or any known dispersal mechanisms ’ (Randall 2002). Very few to none will disperse to 1 km, most 20-200 m.	ML	H

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