St. John's Wort

Hypericum perforatum

Family: Hypericaceae

Description and Life Cycle

A perennial spreading by seeds or short runners. Stems growing to 1 m high, are numerous, erect, and rust coloured at the base. Leaves are opposite, oval, and attached directly to the stem; they appear to be perforated with many tiny translucent dots, visible when held up to a light source. Flowering begins in early summer; flowers are yellow with five separate petals and numerous stamens arranged in three groups. Rust-brown seed pods, containing numerous seeds, mature in late summer to early autumn. Germination occurs in the spring. St. John's wort contains a toxin which, in light-coloured livestock that feed on it, induces photosensitization (skin is irritated and blisters when exposed to sunlight).

Biological Control Agents

• Agrilus hyperici - Beetle
• Aphis chloris - Aphid
• Aplocera plagiata - Moth
• Chrysolina hyperici - Beetle
• Chrysolina quadrigemina - Beetle
• Chrysolina varians – Beetle

References

Cranston, R., D. Ralph and B. Wikeem. 2005. Field guide to noxious and other selected weeds of British Columbia. Gov. of BC. 94 p.

Powell, G. W., A. Sturko, B. Wikeem and P. Harris. 1994. Field guide to the biological control of weeds in British Columbia. B.C. Min. For. Res. Prog.