Hypericum prolificum aka Broombush

Hypericum prolificum is known as shrubby St. John's wort. It belongs to the Hypericaceae family and sheds its leaves. Its native range spans southeastern Canada and the central and eastern United States. Wild plants grow on rocky sites and dry wooded slopes. They also occur beside streams and in damp valleys. This slow-growing shrub forms a dense, rounded mound with upright stems. Most garden plants reach 1–4 feet (0.3–1.2 metres) tall and wide. Some reach about 5 feet (1.5 metres). RHS gives an upper spread of about 5 feet (1.5 metres).

The narrow, dark green leaves grow in opposite pairs. Their edges are smooth, and they lack strong fall color. Young green stems have ridges or slight wings. Older stems become round and woody, with peeling brown bark. The bright yellow flowers have five petals and many stamens. These crowded stamens can hide part of each petal. Flowers grow in small clusters at stem tips and leaf joints. Bloom runs from June through August, sometimes extending into October. Brown, egg-shaped capsules follow the flowers and can last through winter. The fruit attracts birds.

Grow this shrub in sun or partial shade. Full sun gives the best flower display. It prefers moist soil that drains well but tolerates dry spells. It accepts sand, loam, clay, and a wide pH range. It also withstands heat and compacted soil. Missouri Botanical Garden lists USDA zones 3–8; RHS rates it H5. Flowers form on the current year's growth. Early spring is the stated time for pruning. Growers can raise new plants from seed or cuttings. Division offers another way to increase plants.

Use it in shrub borders, native gardens, or rock gardens. Groups can form low hedges or cover banks and slopes. Roots help hold soil on embankments. Underground stems can spread beyond the original clump. UConn reports that plants can escape gardens and naturalize in Connecticut. This makes local spread worth considering before planting. Care needs are low, and major pest problems are uncommon. Root rot and wilt can cause trouble in hot, humid sites. Rust and, less often, honey fungus may also occur.

Do not treat the fruit as food for people or pets. RHS warns against eating it and calls for gloves when handling plants. Sap contact or ingestion can make some people more sensitive to sunlight. Reported effects also include stomach upset, allergic reactions, and fatigue. Eating the plant may reduce the effect of some prescription medicines.