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Biological controls for COMMON ST. JOHNSWORT Coming soon.




Projects Coming soon.





COMMON ST. JOHNSWORT - Hypericum perforaturm L.

Clusiaceae - (St. Johnswort family)

A perennial reproducing by seeds or short runners. Stems are 1 to 3 feet high, erect, with numerous branches, somewhat 2-ridged, rust-colored, woody at their base. Leaves are opposite, sessile, entire, elliptic to oblong, not over 1 inch long, covered with transparent dots. Flowers are 3/4 inch in diameter, bright yellow, numerous in flat-topped cymes, with 5 separate petals with occasional minute black dots around the edges. Petals are twice as long as the sepals. Stamens are numerous, arranged in 3 groups. Seed pods are 1/4 inch long, rust-brown, 3-celled capsules, each with numerous seeds.

St. Johnswort, originally from Europe, is frequently found in the Pacific Northwest, often on sandy or gravelly soils. The weed contains a toxic substance which affects white-haired animals. Affected animals rarely die, but will often lose weight and develop a skin irritation when exposed to strong sunlight. St. Johnswort is an abundant weed in Australia where research has identified three insect species native to Europe which selectively feed on the plant. Insects introduced to the western United States and Canada have provided partial control of the weed.

(Courtesy of Weeds of the West)