Hypericum kalmianum

Kalm’s St. John’s wort is a 1-3 feet tall shrub, largely restricted to the Great Lakes basin of the U.S. and Canada; it is formally listed as “critically endangered” in Illinois (but is quite common in Jackson Park). The flowers occur in clusters (corymbs) of 3-7. Individual flowers are 1-1.25″ across; they have five light green, lance-shaped sepals half the length of the petals, five spreading golden-yellow petals, 150-200 stamens with yellow anthers, and a five-lobed yellow ovary with five (partially or completely fused) styles. The ovary often is markedly five-lobed. The fruit is a teardrop-shaped capsule resting on the five widely-spread sepals containing five (occasionally four) carpels; the capsules are initially green, then turn bright red, then finally brown as the numerous black, oblong seeds mature. Woody lower branches and the strongly five-lobed pistil and fruit are distinguishing characters that separate this species from other Jackson Park St. John’s worts.

Kalm’s St. John’s wort’s lower branches are woody, often with brownish bark peeling off in strips; young stems are four-angled and/or with small wings. The leaves are opposite, arising from the leaf axils, often with smaller, secondary leaves at right angles to the primary leaves; the leaves are dotted with small translucent glands (obvious when the leaf is held up to the light). The primary leaves are up to 2″ long and 3/8″ wide, with the margins of the leaves rolled under; the upper surface is bluish green, the lower surface is light green; both may have a waxy sheen.

Kalm’s St. John’s wort is a 1-3 foot tall shrub, largely restricted to the Great Lakes basin of the U.S. and Canada; it is formally listed as “critically endangered” in Illinois (but is quite common in Jackson Park). Woody lower branches and the strongly five-lobed pistil and fruit are distinguishing characters that separate this species from other Jackson Park St. John’s worts.