Kalmia polifolia aka Bog Laurel

Kalmia polifolia, or bog laurel, is a small evergreen shrub. It belongs to the heath family, Ericaceae. Its native range spans subarctic North America and the north-central and northeastern United States. It grows in cold peat bogs and other wet sites. People have introduced it to Great Britain. Bog kalmia and swamp laurel are other names for it.

Garden plants reach about 2–3 feet (0.6–0.9 m) tall. RHS gives an upper height and spread of 3.3 feet (1 m). Smaller plants may stand just 1 foot (0.3 m) tall. Growth is slow, and stems can form low mats. Some plants grow upright, while others have sparse branches. The bark is gray-brown, with a few shallow cracks. Slender twigs range from red-brown to gray. They have two edges and may feel sticky. The simple leaves grow in opposite pairs along the stems. Their glossy, leathery blades have a dark blue-green cast. The smooth leaf edges roll beneath the blade.

Pink or purple flowers open in spring, often during May and June. Each flower has a bell-like or shallow bowl shape. Small groups hold two to five blooms. Bees visit the flowers and carry pollen between them. Brown, woody capsules follow the blooms, with seeds ripening in September. Each round capsule has five chambers. The evergreen leaves and spring flowers suit borders and woodland gardens. The shrub also fits wet meadows, rain gardens, and shaded beds.

Grow bog laurel in moist, acid soil with organic matter. It accepts sand, loam, or clay and tolerates wet ground. Partial shade suits it well. It also accepts sun when soil stays moist through summer. North Carolina State lists USDA zones 1–5; RHS rates it H5. Sources give about five to twenty years to reach full size. Pruning can remove old growth that would bear next year's flowers. Pests cause few problems, according to RHS. Lime-rich soil can cause iron shortage and yellow leaves. Honey fungus may affect it, but its risk remains uncertain.

No edible use is known, and the whole plant is highly poisonous. Its leaves pose a serious risk to animals. It also harms people, cats, dogs, and horses when eaten. The toxin can disrupt nerves, muscles, and heart function. Honey made from its flowers can also be poisonous. Historical leaf treatments appear in medicinal records, but these do not establish safe use.