Northern Prairie Wildlife Research Center
Marsh St. Johnswort (Triadenum walteri)
- Family: St. Johnswort (Hypericaceae)
- Flowering: August-October.
- Field Marks: Species of Triadenum have 5 pink petals, 9 stamens, and opposite leaves. This one is further distinguished by its blunt sepals and its stalked leaves with black glandular dots.
- Habitat: Swamps, marshes, low woods.
- Habit: Perennial herb with slender rhizomes.
- Stems: Erect, branched or unbranched, smooth, up to 2 1/2 feet tall.
- Leaves: Opposite, simple, oblong to elliptic to ovate, rounded at the tip, tapering to the short-stalked base, without teeth, smooth, with black glandular dots, up to 4 inches long, up to 2 inches broad.
- Flowers: Few in clusters in the axils of the leaves, pink.
- Sepals: 5, greenish, rounded at the tip, up to 1/6 inch long.
- Petals: 5, pink, free from each other, up to 1/3 inch long.
- Stamens: 9, in 3 groups of 3 each.
- Pistils: Ovary superior, styles 3.
- Fruits: Capsules ellipsoid to ovoid, smooth, up to 1/2 inch long, with many brown seeds.
- Notes: The seeds are eaten by waterfowl.
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