Common St. Johnswort; Klamath Weed
Hypericum perforatum* /St. Johnswort Family
Look closely at the leaves to identify St. Johnsworts! I photographed this flower in Oak Ridge in mid-June. Plants in the Hypericum species cause photosensitivity in animals that eat them. For instance, horses, sheep, and goats with white patches (unpigmented areas) on their skin can suffer severe sunburn, swelling, and redness in those areas. The lips, ears and eyelids are especially sensitive. The skin will slough off in severe cases. The toxin is hypericum.
Where seen: Oak Ridge, Great Smoky Mountains NP, Warriors' Path SP