Shrubs, erect, forming round bush, 3–15 dm, bark smooth, not metallic-silvery. Stems: internodes sometimes 4-lined at first, soon 2-winged, not terete. Leaf blades linear, 6–12 × 0.5–0.7 mm, base articulated deciduous with leaf, cf. 8. H. tenuifolium, parallel, margins revolute, apex rounded-apiculate, midrib unbranched. Inflorescences ± narrowly cylindric, 3–15-flowered, with 3–5-flowered dichasia or flowering branches from to 10 proximal nodes. Flowers 10–13 mm diam.; sepals deciduous, not enclosing capsule, 5, linear, unequal, 2.5–4.5 × 0.5–1 mm; petals 5, bright yellow, obovate-spatulate, 5–8 mm; stamens deciduous, 40–45; ovary 3-merous; styles longer than ovaries. Capsules narrowly cylindric to narrowly ovoid-conic, 3.5–5 × 1.5–2 mm. Seeds not carinate, 0.4–0.6 mm; testa finely reticulate. 2n = 18.
Phenology: Flowering summer (Jul–Aug).
Habitat: Moist habitats, pine flatwoods, pond margins, borrow pits, swamp woodland, lowland coastal plain
Elevation: 0–100 m
Ala., Fla., Ga., La., Miss.
Hypericum brachyphyllum is bushier than H. nitidum subsp. exile, with relatively small flowers, capsules, and, usually, leaves, and shorter styles. The bushy habit, two-sided shoots, and glossy leaves without prominent base or apical hydathode, as well as the wet habitats, all distinguish it from H. tenuifolium.