From Flora of Indiana (1940) by Charles C. Deam

This species, described in 2016, is similar to H. kalmianum. According to Wilhelm & Rericha the two can be distinguished by the following:

Larger leaves more than 10 mm wide, broadly obtuse, 3.5–5 cm long, the margins flat or scarcely revolute; dichasia prevailingly 15–31 flowered; larger sepals of proximal central flower 10–12 mm long at anthesis .... Hypericum swinkianum Wilhelm & Rericha

Leaves less than 10 mm wide, obtuse to acute, 2.5–3.5 cm long, the margins usually markedly revolute; dichasia 1–7(–15)-flowered; larger sepals usually less than 10 mm long at anthesis .... Hypericum kalmianum L.

This species was named in honor of Floyd A. Swink (1921 –2000), who studied the natural history and flora of the Chicago region for more than half a century from his base at the Morton Arboretum.

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Indiana Coefficient of Conservatism: C = 10

Wetland Indicator Status: FACW