- St. John’s Wort (Hypericum perforatum) is a perennial plant which can grow up to 1m tall.
- The flowers are bright yellow with five petals, appearing in clusters of up to 100 flowers per stem. The leaves are small and ellipse shaped.
- When held up to the sun, the leaves appear “perforated,” having many small, translucent dots.
- After flowering, capsules form containing many seeds, which can remain viable in the soil for up to ten years.
Consequences of invasion
- St. John’s Wort contains two toxins, hypericin and hypericum red which can cause photosensitivity, weight loss or (rarely) death, if consumed in large quantities by grazing animals.
- The rapid and dense spread of this plant reduces the growth of native species, consequently decreasing amount of appropriate food available for livestock and wildlife.
Introduction and spread
- The plant is native to Europe, western Asia and North Africa.
- As it is used in herbal medicine, it has likely been spread and cultivated for this purpose.
- The plant reproduces by both seed and vegetative reproduction.
- The seeds are easily dispersed by wind, water, animals or human activity and can grow asexually without pollination (apomixes).
- The roots spread laterally and new plants can sprout from these roots, forming an interconnected system of plants.
- Prevention is the most effective option – this plant should not be cultivated for any purpose.
- Select non-invasive plants for your garden, become PlantWise.
- Removing only the stems stimulates regrowth as the root system is difficult to remove.
- Tilling the soil and then immediately replanting with other perennial grasses may be effective.
- Two biocontrol beetles have been released in BC (Chrysolina spp.) with some success.
- Other biocontrol agents are still being researched.
- Chemical control may be an option in certain situations, contact a local professional to determine whether this will be appropriate.