Corydalis cava aka Hollowroot

Corydalis cava is a small perennial in the poppy family, Papaveraceae. Its common names include hollow root, hollow wort, and holewort. Its native range runs from Europe to the Caucasus. It grows in temperate regions and lives in shady forests. It also occurs among shrubs, though less often. It is not native to Britain or Ireland.

This plant grows from a tuber and forms small clumps. Its leaves divide into groups of three and are deciduous. The RHS describes plants about 0.7 feet [0.2 metres] tall. Its broader garden height range reaches 1.6 feet [0.5 metres]. The listed spread reaches about 0.3 feet [0.1 metres]. Chicago Botanic Garden describes its shape as a low mound. These small dimensions suit the front of a shaded border.

Flowers appear in early spring, with March to April listed in Chicago. They grow in clusters at the tips of stems. The RHS records white or purple blooms, each about an inch long. Chicago also lists pink among the flower colours. The blooms bring spring colour to beds and shaded borders. Woodland gardens and shaded edges are other suggested settings. The RHS also suggests rock gardens and informal cottage plantings. It lists the plant for use beneath roses and shrubs.

Give it partial shade and moist soil that drains well. Chicago also lists full shade as a suitable exposure. The RHS recommends humus-rich soil with a moderate level of fertility. It accepts clay, loam, sand, and chalk-based soils. Acid, neutral, and alkaline conditions all fall within its listed range. Chicago gives a moderate watering requirement and USDA zones 4–7. The RHS rates its UK hardiness as H5. It lists two to five years to reach full size.

Routine pruning is not needed, according to the RHS. That source reports few usual pest or disease problems. Sow ripe seed in containers kept in an open frame. Division in autumn offers another way to raise more plants. Plants For A Future records no known edible uses. It reports medicinal use of the tuber, with trained supervision required. That record does not establish that home use is safe. Its toxicity warning concerns the genus, not confirmed evidence for this species.