Swink's St. John's wort is a many-branched shrub up to high. It has exfoliating bark. The leathery, oblong leaves reach in width and in length, with weakly
revolute edges. The flowers are produced in terminal flowerheads known as
dichasia. Each dichasium produces 7-31 bright yellow flowers, each with 5 petals and numerous yellow
stamens. The capsules are 5-parted. In the Chicago Region, it blooms between July and August.
Hypericum swinkianum differs from the closely related
Hypericum kalmianum by its notably larger vegetative features, flowerheads each averaging more than 7 flowers, and an affinity toward acidic rather than calcareous habitats. ==Distribution and habitat==