Corydalis flavula aka Yellow Harlequin

Corydalis flavula, or yellow fumewort, belongs to the poppy family, Papaveraceae. This annual grows in temperate parts of North America. Its native range spans southeastern Canada and central and eastern United States. It grows in open woods, flood plains, glades, and slopes. It also occurs on outcrops of mafic rock. In North Carolina, it reaches from western areas through the Piedmont. Floods and other disturbance help create the open sites it needs.

Plants grow 0.33–1 foot [0.1–0.3 metres] tall. They spread about 0.5–0.67 feet [0.15–0.2 metres] across. Several stems branch near the ground. They may stand upright or lean along the soil. Growth is fast, but the plant has a short life. It sets seed, then dies back, often by May. It readily seeds itself where conditions suit it. The flowering stalks are pale green, sometimes with a red tint.

The smooth leaves have a green-gray cast and lack hairs. Compound leaves at the base have two leaflets with small lobes. They reach about 0.25 feet [0.076 metres] long. Their width reaches about 0.17 feet [0.051 metres]. Smaller leaves grow in an alternate pattern along the stems. Yellow, tube-shaped flowers rise above the basal leaves. They bloom from late winter into early spring. Racemes form at the tips of the flowering stems. Each flower has a toothed upper petal that curves upward. Green, pod-shaped capsules follow the flowers in spring. These hold black seeds.

Choose a site with dappled light or partial shade. Humus-rich loam with good drainage suits this plant. Keep the soil moist rather than poorly drained. The NC State account gives conflicting guidance on soil pH. Its main text favors high pH, while its soil table lists acid conditions. That conflict leaves its preferred pH uncertain. The plant needs little routine care. Seed is the recommended means of propagation.

Yellow fumewort suits small groups in shaded native gardens. It also fits woodland plantings and areas left to naturalize. Its early flowers supply nectar for bees. Deer resistance adds to its value in these settings. NC State lists no major pest or disease problems. Habitat loss threatens it in some places, including Michigan. Native Americans used the plant for medicine.