21. Hypericum ellipticum Hooker, Fl. Bor.-Amer. 1: 110. 1831.
Pale St. John’s wort, millepertuis elliptique Pale St. John’s wort, millepertuis elliptique
Brathydium canadense Spach; Hypericum brathydium Steudel; H. canadense Linnaeus var. oviforme R. Keller
Herbs, perennial, erect, with creeping, rhizomatous, ± woody base, usually unbranched, sometimes branched proximally, relatively slender, 1.1–3(–5) dm. Stems: internodes 4-lined. Leaf blades broadly to narrowly elliptic or oblanceolate to oblong-elliptic, 11–35 × 3–13 mm, base not articulated, cuneate to shallowly cordate-amplexicaul, margins plane to subrevolute, apex rounded, midrib with 5–7 pairs of branches. Inflorescences <corymbiform>, (1–)3–15-flowered, narrowly branched, sometimes with branches from 1–2 proximal nodes. Flowers 12–15 mm diam.; sepals persistent, not enclosing capsule, (4–)5, ± lanceolate to lanceolate-elliptic, ± unequal, 6–7 × 2–3 mm; petals (4–)5, pale yellow, sometimes tinged red, obovate to oblanceolate, 6–8 mm; stamens persistent, 70–95; ovary 3-merous, <placentation parietal>. Capsules ellipsoid to globose, 4–7 × 3.5–5 mm. Seeds carinate, 0.6–0.7 mm; testa scalariform-reticulate. 2n = 16, 18.
Flowering summer (Jun–Sep). Stream, lake, and pond margins, wet meadows, swamps; 0–600 m; N.B., Nfld. and Labr. (Nfld.), N.S., Ont., Que.; Conn., Ill., Maine, Md., Mass., Mich., Minn., N.H., N.J., N.Y., Ohio., Pa., R.I., Tenn., Vt., Wash., W.Va., Wis.
Hypericum ellipticum is related to H. sphaerocarpum, differing by the shorter, herbaceous, rhizomatous habit, shorter leaves, and smaller seeds. A submerged aquatic form (forma submersum Fassett) and one with axillary branches developing after fertilization (forma foliosum Marie-Victorin) seem scarcely worth formal recognition. Hypericum ellipticum is introduced in Washington.