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Background:
Imperforate St. John's wort was recently introduced tothe U.S. from Europe. Imperforate St. John's wort is a rhizomatous perennial, similar to common St. John's wort. Imperforate St. John's wort has stems with 4 raised lines or wings, whereas common St. John's wort stems are 2 lined. Imperforate St. John's wort leaves are larger and more ovate (egg-shaped) or ovate-lanceolate (lance-shaped) with densely reticulate (net-like) venation; while leaves incommon St. John's wort are ovate to linear (long and narrow with parallel sides) with obscurely reticulate venation and with numerous translucent dots. St. John's wort is invasive as well as toxic to livestock.

Description:
A perennial with shoots up to three feet tall arising from a creeping rhizome; stems are square in cross section with 4 raised lines and leaves about 3/4 inch long, without translucent glandular dots or with few large ones in the upper leaves. Flowers are bright yellow with five petals and are about 3/4 inch across. The black dots often visible along the petal margins are glands containing hyericin.

Habitat:
Found in open woodland, grassland, railway, and road embankments.

Distribution:
A common native in Europe; in the Pacific Northwest, it has been confirmed in on ly one area in Bonner County, ID in 2002. (See Map)