Macquarie Valley Weeds Committee & Lachlan Valley Weeds Advisory Committee


St John's Wort

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Botanical Name: Hypericum perforatum
Other Common Names:


Class Regions
Class 3Bland Shire Council
Class 4Cabonne Council,Castlereagh Macquarie County Council,Cootamundra Shire Council,Cowra Council,Forbes Shire Council,Lachlan Shire Council,Mid-Western Regional Council,Narromine Shire Council,Orange City Council,Parkes Shire Council,Upper Macquarie County Council,Weddin Shire Council,Wellington
Landholder Responsibilities: Class 4 - growth and spread of the plant must be controlled according to the measures specified in a management plan published by the local control authority and the plant may not be sold, propagated or knowingly distributed. Class 3 - The plant must be fully and continuously suppressed and destroyed
Why Is It Bad?: St. John's Wort has shown itself to be a significant weed in the group project area by its ability to grow in all climatic and topographical zones. It has also shown itself to become a dominant species, replacing native and improved pastures. St. John's Wort's capacity to replace desirable plant species and its effect on stock health (photosensitization) makes it a threat to agricultural/horticultural production.


Habit: Herb
Leaves: Leaves opposite, sessile with oil glands which appear to be perforations when held up to the light.
Flowers: Flowers of 5 yellow petals with several stamens occur in 3 bundles.
Fruit: Fruit is a sticky 3- celled capsule containing many seeds. The long-term viability of St. John's Wort seed can be up to 10 years.
Roots: Rhizomatous

Control Methods

Manual Removal: St John�s Wort can reproduce from buds on its roots therefore the entire root structure must be removed.
Chemical Use: Different situations (e.g., flowering times, chemical choice, surrounding plants) require different methods (e.g. spot spraying, wick wiper).
Fire: Non-specific, it kills seeds and checks growth.
Slashing & Cutting:
Biological Control: Agents include two species of Chrysolina beetles, Agrilus hyperici, Gall midge, Aphic chloris, and the St John�s Wort stunt mite.
Grazing: Practical for steep, inaccessible hill country. Only certain breeds of sheep with enough wool growth or dark coloured cattle should be used.
Cultivation & Scalping:
Competition: Perennial pastures provide competition that is essential for long term control, particularly during autumn.
Monitoring: Successful treatment programs rely on ongoing monitoring of sites. Regrowth and new seedlings can easily become larger infestations if follow-up treatments are not part of the management program.


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Image Credit: Cath Kearney

Image Credit: Cath Kearney

Image Credit: Megan Power

Image Credit: Megan Power

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