ABSTRACT
There are over 400 species of Hypericum distributed worldwide. The plants are glabrous, erect perennials with yellow, five-petaled flowers and sessile, opposite, ovate-linear leaves with translucent glands appearing as red dots. Hypericum perforatum blooms from June to September. It should not be confused with the ornamental ground-cover rose of Sharon (H. calycinum), commonly planted around buildings, in gardens, and parks. Hypericum perforatum is native to North Africa, the Azores, Madeira, West Asia, and Europe. In the United States, it is especially abundant in Northern California and Southern Oregon, an area from which it derives one of its common names, Klamath weed (Hobbs, 1989).
