Boundary Invasive Species Society
St. John's wort
St. John's wort (Hypericum perforatum) has increased in recent years. With several large infestations in the Boundary. There was a large infestation in the path of the 2015 fire in the Rock Creek-Westbridge area.
St. John's wort is a perennial that grows from underground runners. It grows from 0.3 to 1 m in height. Transparent dots are visible over the surface of the oblong leaves when held to the light. It has bright yellow flowers with 5 petals. Plants turn a rusty red colour at maturity.
St. John's wort is controlled by bio-agents. Mainly Chrysolina species beetles. There was a crash in insect populations but the past few years have shown a rise in populations. Selective herbicides are effective.
St. John's wort contains a toxin that causes grazing animals to become sensitive to sunlight resulting in intense skin irritation. St. John's wort is also used medicinally for depression but you should speak to a health care professional before taking it as it can cause photo sensitivity and can cause liver failure if you take too much.