St. John's-wort has two-sided, rust-red stems and numerous clusters
of bright yellow flowers with five distinctly separate petals. Its oblong
leaves have prominent veins and are covered with dots which are transparent
when the leaves are held up to the light. Mature plants grow to 1 m in
height and turn a rusty red.
St. John's-wort invades grazed and disturbed lands. In dense stands,
it displaces native plant species and reduces livestock and wildlife forage.
The plant also contains a toxin that causes skin irritation and blistering
in light-coloured livestock when they are exposed to sunlight.
In British Columbia, St. John's-wort grows at low to mid-elevations
in coastal, grassland, and open forested regions, and along roadsides
and disturbed areas. It occurs in scattered pockets in the Kootenays,
Okanagan, Boundary, North Thompson, Cariboo, Skeena, Fraser Valley, and
Vancouver Island areas.
The root system spreads laterally and is capable of forming new buds that
separate from the parent. Seeds have a gelatinous coat that facilitates