Northern Prairie Wildlife Research Center


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Aquatic and Wetland Vascular Plants of the Northern Great Plains

17. Clusiaceae, the Mangosteen Family

1. Hypericum L. -- St. John's-wort

1. Hypericum majus (A. Gray) Britt. -- Greater St. John's-wort

Annual or often perennial from short leafy stolons at the plant base. Stems upright, simple or branching above, 1-5 dm tall, ridged due to the decurrent leaf bases. Leaves lanceolate to oblong, 1-4 cm long, 2-11 mm wide, glandular-punctate, with minute brownish-translucent glands, 5-to 7-nerved from the base, with 3 major veins continuous to the obtuse or rounded tip, broadly rounded to somewhat cordate and clasping at the base. Flowers few to numerous in terminal cymes. Sepals lanceolate, mostly 3-5(7) mm long, acute; petals yellow, about equaling the sepals, somewhat marcescent and shriveling to ca. 1/2 the length of the sepals; stamens 15-35, free; styles 1 mm or less long, each with a capitate stigma, ovary 1-celled. Capsule often purplish, ovoid-conic, 5-7 mm long; seeds yellowish, narrowly ellipsoid, ca. 0.5 mm long. Mid Jul--Sep. Sandy wet meadows, shores and ditches; scattered but most common in NE Sand Hills; (Que. and Newf. to B.C., s to PA, NJ, IL, IA, KS and CO).

Reports of Hypericum canadense L. in the northern Great Plains are based on misidentifications of H. majus.

GIF-Hypericum majus
Hypericum majus GIF- Distribution Map
Map key

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