Collinsonia canadensis aka Northern Horsebalm

Collinsonia canadensis is a perennial wildflower in the mint family. Common names include horsebalm, richweed, and northern horsebalm. It grows in eastern North America, from Canada into the United States. Its range reaches south to Florida. Wild plants grow in rich woods, ravines, and wooded slopes. Some sites have limestone soils. It also grows in moist forests with rich soil.

Garden plants often reach 2–3 feet (0.61–0.91 metres) tall. Some reach 4 feet (1.22 metres). Their spread reaches 1–3 feet (0.30–0.91 metres). Plants grow upright and spread through underground rhizomes. Growth is fast, and the leaves fall each year. The pale green stems have four blunt edges and shallow grooves. They have few hairs or none. Large, oval leaves grow in pairs along the stems. Their edges have teeth, and their undersides look paler. Crushed leaves give off a scent like lemon or citronella.

Small, pale yellow flowers form loose, branched clusters at stem tips. The clusters have a broad, tapering shape. Each flower forms a tube with two lips. The fringed lower lip extends beyond the upper one. Flowers carry the same lemon-like scent as the leaves. Bloom runs from July to September, though one source lists August to September. Small nutlets form within enlarged calyces during September and October. Bees visit the flowers for nectar. The plant also draws birds, moths, and bumblebees. Its leaves feed larvae of the stoneroot borer moth.

Horsebalm suits woodland, wildflower, and native plant gardens. It also fits areas where plants can spread on their own. Partial shade suits it best, though it tolerates deep shade. It grows well beneath trees that shed their leaves. Choose moist soil that drains well and contains humus. Loam suits it, but sandy and clay soils also work. It accepts slightly acid to neutral soil and some dry spells. Sources place it in USDA zones 4–8. Division offers a way to raise more plants. No serious insect or disease problems are reported. However, one source flags its spreading growth as weedy.

Two sources report using the leaves for tea. Another lists no known edible uses and warns about fresh leaves. Even small amounts may cause vomiting; blood pressure may also rise. Roots have a history of herbal use for urinary and kidney complaints. These records describe past uses, not proof of safe treatment.