St John's Wort

(Hypericum perforatum)

What is St John's wort?

St John's WortGeneric Weed Distribution Map

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  • St John's wort is a weed of pastures, open bushland and roadsides.
  • St John's wort is a declared weed in Tasmania under the Tasmanian Weed Management Act 1999. The importation, sale and distribution of St John's wort are prohibited in Tasmania.

How to identify St John's wort

  • St John's wort is a perennial (long-lived) herb growing to between 30 and 70 cm and occasionally to 1.2 metres high. The reddish stems arise from the rootstock or woody crown.
  • St John's wort has a main root extending to 1 metre deep and horizontal rhizomes (underground stems) just below the surface producing buds from which new above-ground growth develops each year.
  • The leaves are stalkless and hairless and have numerous small oil glands that give the leaf a perforated appearance when held up to the light. The flowers are bright yellow with black glands dotted along the margins of the petals, and grow in numerous clusters at the end of the branches. The fruit is a sticky capsule containing numerous, dark brown or black cylindrical seeds.
  • A related weed, square-stemmed St John's wort (also called St Peter's wort) is similar to St John's wort, but stems are almost square in cross-section, and the leaves are oval to oblong, often heart-shaped, and stem clasping at the base.
  • For further help in identifying St John's wort, search the Dennis Morris Weeds and Endemic Flora database for St John's wort illustrations. If you are still in doubt about the weed you are dealing with, contact your Regional Weed Management Officer on 1300 368 550 for help.
St John's Wort St John's Wort
Image top: St John's wort (K Stewart)
Image above left: St John's wort (K Stewart)
Image above right: St John's wort (K Stewart)

St John's wort in Tasmania

  • St John's wort occurs as a localised weed of roadsides, poorly managed grazing land, neglected areas and disturbed bushland areas of Tasmania, particularly in the northern Midlands, north-east, central north coast and the south east (see map).
  • St John's wort is a threat to the grazing industry due to its toxicity to stock, and its ability to compete with desirable pasture species in poorly managed pastures.
  • St John's wort is also an environmental weed and can out-compete native species, with open grassland-woodland communities most affected.

What is the legal status of St John's wort in your area?

  • The legal responsibilities of landholders and other stakeholders in dealing with St John's wort are laid out in the Statutory Weed Management Plan for St John's Wort.
  • Use Table 1 (Zone A municipalities) in the Statutory Weed Management Plan to find out whether your area falls in an eradication or containment zone.

Detailed management and control guidelines for St John's wort can be found in the St John's Wort Control Guide. Refer also to Herbicides for St John's Wort Control. For further information see DPIPWE's Weed Links and Resources.

See also
St John's Wort Control Guide
Herbicides for St John's Wort Control
Statutory Weed Management Plan for St John's Wort
Weed Links and Resources

Other useful links

Pest Genie
Weeds in Australia - Weed Management Guide

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