Herbs annual or perennial, erect, basal branches relatively few or none, usually with strict, ascending branches from distal nodes, 0.3–7.5 dm. Stems: internodes 4-angled. Leaves erect or spreading, sessile or subsessile; blade linear to oblanceolate-linear or (proximal) oblanceolate to obovate, 6–55 × 0.5–5.5 mm, papery to membranous, margins plane, apex rounded, basal or near-basal veins 1–3(–5), midrib with 1–4 pairs of branches. Inflorescences corymbiform to cylindric, , 1–35-flowered, branching mostly dichasial. Flowers 5–6 mm diam.; sepals linear-lanceolate to lanceolate, equal, 2.5–4.5 × 0.8–1 mm, , apex acute to acuminate; petals golden yellow, , narrowly obovate to elliptic, 2.5–4 mm; stamens 12–25, obscurely 3–5-fascicled; styles 0.5–0.8 mm; stigmas broadly capitate. Capsules narrowly conic to conic-cylindric, 4–6 × 1.5–3 mm, . Seeds 0.5–0.7 mm; testa finely linear-scalariform. 2n = 16.
Annual, or perennating by short, leafy stolons; stems slender, erect, 1–6 dm; lvs linear to narrowly oblanceolate, 1–4 cm × 1–4(–5) mm, obtuse, tapering to the narrow base, 1-nerved or weakly 3-nerved; infl compact to more often loose, usually with fewer fls than no. 21; bracts subulate; sep lanceolate, acute or acuminate, 3–5 mm; pet 2.5–3 mm; stamens 12–22; styles 3(4), under 1 mm; fr purple, mostly conic, 4–6 mm; seeds 0.5 mm; 2n=16. Sandy or muddy shores or wet meadows; Nf. and Que. to Minn., s. to Ga. and Ala., more common eastward. July–Sept. Hybridizes with several other spp.; one such apparent hybrid, approaching no. 21 [Hypericum mutilum L.] or 22 [Hypericum boreale (Britton) E. P. Bicknell], has been called H ×dissimulatum E. P. Bicknell.
|Irish St John’s-wort||English||IE|
|Canadian St. John’s wort, millepertuis de Canada|