Saint John's Wort

Saint John’s wort was introduced from Europe as a garden plant and for medicinal purposes in the 19th century; unfortunately because of its aggressive weedy characteristics it readily invades pastures, bushland and grasslands. In South Gippsland it can be seen along railway reserves and some pastures. It has become highly invasive in the east of the state. It has clusters of bright yellow 5 petal flowers, the leaves are small and dotted with oil glands and gives a perforated appearance when held up to the light. Flowers early spring through summer, becoming reddish-brown in late autumn-winter because of mature fruits and old stems. Up to 30000 seeds can be produced from each plant annually and can last for 12 years in the soil. It is spread mainly by wind, machinery slashing and contaminated fodder. Saint John’s wort contains the alkaloid hypericin, which causes photosensitisation in any mammals that ingest it, resulting in blisters on weakly pigmented parts of the skin. Small plants can be removed by hand as long as all plant and rhizomes are removed. Larger infestations can be controlled with appropriate herbicide. In South Gippsland Saint John’s wort is classified noxious, regionally controlled which means it can not be sold or transported and landholders are expected to control and prevent its spread on their land.