It was named after Chicago Region botanist Floyd Swink (1921-2000).

[3] Swink's St. John's wort is a many-branched shrub up to 1.8 meters (5.9 ft) high.

[3] 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.

[1] Swink's St. Johns wort is known to occur in sand flatwoods and acidic wet to wet-mesic sand prairies in the western Great Lakes region in the United States, including Illinois, Indiana, and Michigan.

[1][3] It is a highly conservative species with a coefficient of conservatism of 10 in the Chicago Region[3] and in Michigan.