This perennial produces a toxin which, when consumed, causes white-skinned animals to develop massive skin lesions when exposed to the sun. The leaves are small, hairless, and opposite. When held up to the light, one can see numerous `perforations` which are actually clear, window-like glands that produce the toxin. Three biocontrol agents have been released on this species; the most noticeable is an iridescent black beetle which feeds on the leaves. Also called goatweed and Klamathweed.