St John's wort

Native to Europe, western Asia and northern Africa, St John's wort is a woody perennial herb with bright yellow flowers. It is grown for use as an anti-inflammatory, astringent and antiseptic.

St John's wort is a weed in more than 20 countries. It invades woodlands and pastures and is poisonous to livestock. Small populations currently exist in southern Queensland, and the species has the potential to spread further across cooler, upland areas in this region.

St John's wort is not a prohibited or restricted invasive plant under the Biosecurity Act 2014.

Scientific name

Hypericum perforatum

Other names

  • Common St John’s wort, goatweed, Klamath weed

Similar species

  • H. gramineum, H. japonicum

Description

  • Perennial herb with woody stems 30-120cm tall in spring and summer.
  • Stems have 2 opposite longitudinal ridges.
  • Leaves are opposite, ovate to oblong, dotted with tiny, translucent, black oil glands.
  • Flowers are bright yellow, 1-2cm in diameter with 5 petals.
  • Fruits are sticky, 3-chambered capsules, containing densely pitted seeds about 1mm long.

Habitat

  • Can tolerate soils ranging from dry, rocky and shallow to deep and fertile.
  • Found in grasslands, woodlands, pastures and forest plantations, and along riverbanks, roadsides and railway lines.

Distribution

  • Found in small populations near Stanthorpe and Toowoomba.

Life cycle

  • Flowers late spring and summer.
  • Produces 15,000-33,000 seeds annually.
  • Seeds remain dormant for 4-6 months before germinating.
  • Germinates from autumn to spring.

Affected animals

  • Livestock

Impacts

Economic

  • Invades woodlands and pasture.
  • Poisonous to livestock.

How it is spread

  • Seeds and capsules are spread by water.
  • Fruit can stick to machinery, tyres, shoes, clothing and animal fur.

Control

Biological control

  • Low level of biological control has been achieved in some areas in southern Australia with 2 Chrysolina beetles and the mite Aculus hyperici.
  • Other insects are used in biological control programs in North America and New Zealand.

Legal requirements

  • St John's wort is not a prohibited or restricted invasive plant under the Biosecurity Act 2014. However, by law, everyone has a general biosecurity obligation (GBO) to take reasonable and practical steps to minimise the risks associated with invasive plants and animals under their control.
  • Local governments must have a biosecurity plan that covers invasive plants and animals in their area. This plan may include actions to be taken on certain species. Some of these actions may be required under local laws. Contact your local government for more information.

Further information