Invasiveness Assessment - St. John's wort (Hypericum perforatum) 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 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: St. John’s wort
Scientific name: Hypericum perforatum

Question	Comments	Reference	Rating
Establishment
Germination requirements?	Seeds germinate in autumn, winter or spring.	P & C (1992)	MH
Establishment requirements?	Would receive some shading where occurring as an environmental weed.	Carr et al (1992)	MH
How much disturbance is required?	Is a ‘very serious’ weed of lowland grassland and grassy woodland, dry sclerophyll forest and woodland, damp sclerophyll forest and riparian vegetation.	Carr et al (1992)	MH
Growth/Competitive
Life form?	Perennial herb.	P & C (1992)	L
Allelopathic properties?	None described.		L
Tolerates herb pressure?	“Stock eat St. John’s Wort only when other feed is scarce”.	P & C (1992)	MH
Normal growth rate?	“Competes throughout the year with other species for light and nutrients and when firmly established, eliminates all other plants”. “Whilst St. John’s Wort once established, competes strongly with other plants, in itself is very sensitive to competition in the young stages”. P & C (1992 p. 391)	P & C (1992)	MH
Stress tolerance to frost, drought, w/logg, sal. etc?	Tolerant of frost and drought.	P & C (1992)	M
Reproduction
Reproductive system	Reproducing from crowns, rhizomes and by seed.	P & C (1992)	H
Number of propagules produced?	“Seed production is prolific and a single plant may produce 33,000 seeds in a season”.	P & C (1992)	H
Propagule longevity?	“Some seeds last at least 10 years in the soil but most germinate in the first few years”.		L
Reproductive period?	Forms dense infestations. (See pic. Campbell et al 1995 p. 152)	Campbell et al (19950	H
Time to reproductive maturity?	Plants generally do not flower in the first year.		MH
Dispersal
Number of mechanisms?	“Seeds are very small and readily dispersed in water, mud, soil and agricultural produce”. Cultivation can also spread pieces of rhizome. Seed capsules adhere to the wool and fur of animals.	P & C (1992)	MH
How far do they disperse?	“The seed can be dispersed short distances by wind and long distances by man and water. (Parsons 1973)” - (Campbell et al 1995).		MH

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