17. Hypericum cistifolium Lamarck in J. Lamarck et al., Encycl. 4: 158. 1797.
Hypericum opacum Torrey & A. Gray; H. punctulosum Bertoloni; H. rosmarinifolium Lamarck
Shrubs, erect, unbranched or with relatively short branches and sometimes 1–2 branches ascending from proximal nodes, 5–13 dm. Stems: internodes 4-lined at first, then terete. Leaf blades narrowly oblong or narrowly elliptic-oblong to triangular-lanceolate, 15–40 × 2–10 mm, base not articulated, cuneate to subcordate, margins recurved, apex subacute to rounded, midrib with 1 pair of branches. Inflorescences <corymbiform to cylindric>, (7–)15–65-flowered, narrowly branched, sometimes with 3–65-flowered dichasia from 1–2 proximal nodes and relatively short, flowering branches from further 1–4 nodes. Flowers 7–12 mm diam.; sepals persistent, not enclosing capsule, 5, obovate or broadly elliptic to oblong, unequal, 2–4 × 1–1.7 mm; petals 5, bright yellow, oblanceolate, 5–8 mm; stamens (some or all) persistent, 30–50; ovary 3-merous, <placentation parietal>. Capsules ovoid-cylindric to broadly ovoid, 4–6 × 3–4 mm. Seeds not carinate, 0.6 mm; testa reticulate to linear-foveolate. 2n = 18.
Flowering spring–early fall (Apr–Oct). Pine flatwoods, margins of bogs, swamps, and marshes, ditches, on sand, coastal plain; 0–300 m; Ala., Fla., Ga., La., Miss., N.C., S.C., Tex.
Hypericum cistifolium is woodier in habit than H. sphaerocarpum and has shorter leaves, smaller flowers, narrower sepals, narrower capsules, and smaller seeds.