Hypericum ascyron (Great St. Johnswort) is a species of perennial herb in the family Hypericaceae. They have a self-supporting growth form. They are native to Canada, The Contiguous United States, and Australia. They have simple, broad leaves and yellow flowers. Flowers are visited by Mallota posticata, Grey Flesh fly, Pherbellia parallela, and Pipiza femoralis. Individuals can grow to 5 feet.
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