[5] Atlantic St. John's-wort is a small, spreading shrub, growing 10–50 cm (3.9–19.7 in) tall and forming mats.

Each flower is 10–14 mm (3⁄8–1⁄2 in) broad with 5 sepals, 5 bright yellow petals, and 50-90 stamens.

The ovaries are three-parted, forming cylindric capsule fruits.

It flowers in the summer, typically June through September, but sometimes as late as December.

[4] Hypericum tenuifolium occurs in the Atlantic coastal plain in the southeastern United States, in Alabama, Florida, Georgia, North Carolina, and South Carolina.