Shrub to 1 m tall Leaves: opposite, bluish green above, covered with a waxy whitish coating (glaucous) and dotted with transparent glands beneath, 2 - 4 cm long, 3 - 8 mm wide, linear to narrow-oblong, non-toothed and usually curling under slightly (revolute), firm. Flowers: borne in 2 - 3.5 cm wide terminal inflorescences of three to seven flowers, with 3 - 4 mm wide sepals that are broad elliptic to inversely egg-shaped with a rounded tip, five yellow petals 10 - 16 mm long, numerous stamens, and five styles. Fruit: a five-chambered capsule, 7 - 10 mm long, narrow egg-shaped, beaked, many-seeded. Bark: peeling, papery white to multicolored. Twigs: brown and four-angled.
Similar species: Hypericum prolificum and Hypericum kalmianum are the only shrubby Hypericum species in the Chicago Region. Hypericum prolificum grows to 2 m tall, has shedding gray outer bark and pale orange inner bark, two-ridged twigs, leaves greater than 8 mm wide, flowers with 7 - 10 mm long petals and four styles, and three-chambered capsules.
Flowering: mid June to early October
Habitat and ecology: Locally common near interdunal ponds by Lake Michigan, growing in moist calcareous sand. This species also occurs in small bogs that formed after sand removal and in calcareous swale borders.
Occurence in the Chicago region: native
Etymology: Hypericum is the Greek name for St. John's Wort, which blooms around St. John's Day (June 24). Kalmianum is named after Peter Kalm, the discoverer of this plant and a student of Linnaeus.
Branching shrub to 1 m; lvs firm, often revolute, articulate at the base, linear to narrowly oblong, 2-4 cm נ3-8 mm; fls 2-3.5 cm wide, in small cymes of 3-7 terminating the branches; stamens very many, distinct; styles (4)5; fr (4)5-locular, narrowly ovoid, 7-10 mm, the style-base persistent as a slender beak; 2n=18. Dunes and rocky shores about Lakes Erie, Huron and Michigan; inland in c. Wis. and along the Ottawa R. in Que. Late June-Aug.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.