Article from Bean's Trees and Shrubs Hardy in the British Isles
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'Hypericum densiflorum' from the website Trees and Shrubs Online (treesandshrubsonline.
An evergreen shrub 2 to 4 ft high (6 ft in the wild); branches erect, two-angled. Leaves 1 to 2 in. long, usually less than 1⁄4 in. wide, linear-lanceolate, recurved at the edges. Flowers very numerous, in compact cymose panicles; each flower 1⁄2 in. across. Fruits three-celled, slender, 1⁄4 in. long, subtended by the five oval-oblong, spreading sepals.
Native of the pine-barrens from New Jersey to Florida, and from Kentucky west to Arkansas and Texas. It is a near ally of the commoner H. prolificum, but is smaller in flower and narrower in leaf; its fruit also is more slender.
H. lobocarpum Gattinger H. densiflorum var. lobocarpum (Gattinger) Svenson – Capsule deeply lobed, four- or five-celled; styles four or five. N. Carolina to Louisiana.