Sp. Pl. 2: 787. 1753.
Herbs annual or perennial, erect, usually unbranched proximal to inflorescence, 2–8 dm. Stems: internodes 4-lined, scabrous-tomentose to pilose. Leaves appressed to ascending, sessile; blade narrowly ovate or lanceolate to narrowly oblong-elliptic (or proximal oblanceolate), 4–15 × 1.5–7 mm, subcoriaceous, margins recurved, apex acute to obtuse, surfaces scabrous-tomentose to pilose, basal veins 1(–5), midrib with 0–1 pair of branches. Inflorescences cylindric to subcorymbiform, to 30-flowered, branching mostly dichasial. Flowers 5–11 mm diam.; sepals ovate to ovate-lanceolate or obovate, subequal, 2.5–5 × 1.5–2.5 mm, margins setulose-ciliate, apex acute; petals 5, deep yellow, obovate, 4–7 mm; stamens (15–)20–40, filaments almost distinct; styles 1.5–2 mm; stigmas ± broadly capitate. Capsules ovoid to ellipsoid-subglobose, 3.5–5 × 2–3 mm. Seeds 0.4–0.6 mm; testa linear-reticulate. 2n = 12.
Phenology: Flowering early–late summer (Jun–Sep).
Habitat: Wet ditches, bogs, savannas, wet pinelands on sandy soil
Elevation: 0–200 m
Ala., Fla., Ga., La., Miss., N.C., S.C., Tex., Va.
Hypericum setosum is the only American Hypericum sp. with an indumentum. It is related to H. virgatum (H. denticulatum subsp. acutifolium); in addition to having the indumentum, it is generally smaller and less branched and has a different chromosome number.