St John's Wort is the plant species Hypericum perforatum, also known as Tipton's Weed, Chase-devil, or Klamath weed. It is sometimes called Common St John's Wort to differentiate it. St. John's Wort is widely known as a herbal treatment for depression. Hypericum perforatum is a yellow-flowering, perennial herb indigenous to Europe, which has been introduced to many temperate areas of the world and grows wild in many meadows. The common name comes from its traditional flowering and harvesting on St John's day, 24 June. The species name perforatum refers to the presence of small oil glands in the leaves that look like windows, which can be seen when they are held against the light. Although Hypericum perforatum is grown commercially in some regions of south east Europe, it is listed as a noxious weed in more than twenty countries and has introduced populations in South and North America, India, New Zealand, Australia, and South Africa. In pastures, St John’s Wort acts as both a toxic and invasive weed. It replaces useful vegetation to the extent of making productive land unviable or acts as an alien species in natural ecosystems. Ingestion by livestock can cause photo-sensitisation, central nervous system depression, spontaneous abortion, and can lead to death.
Identification: St John’s Wort can be visually recognized by leaf and flower type. Yellow, five-petaled flowers approximately 20 mm across occur between late Spring and early to mid Summer. Leaves exhibit obvious translucent dots when held up to the light, giving them a ‘perforated’ appearance, hence the plant's Latin name. When flower buds (not the flowers themselves) or seed pods are crushed, a reddish/purple liquid is produced.