Culture
Best grown in rich, evenly moist but well-drained soils in light to moderate shade including sun-dappled conditions. Soils must never dry out during the growing season, but should be kept uniformly drier in winter where wet soils can be fatal. Best performance generally occurs in cool summer climates such as the Pacific Northwest where plants may flower from spring to fall. By contrast, plants generally grow poorly in the hot and humid summer conditions of the deep South where they typically go dormant by mid-summer. Plants prefer basic soils. Add lime to acidic soils. Propagate by division or seed immediately after flowering.
Noteworthy Characteristics
Corydalis flexuosa, commonly known as blue corydalis, is an upright, rhizomatous, often summer-dormant perennial that grows to 12-15” tall spreading by rhizomes to 18” wide or more. It is native to forests, clearings, grassy slopes and riversides in China (Sichuan Province). Finely-divided, glaucous, two-ternate, lacy green leaves (to 6” long) with ovate leaflets form a foliage clump (to 12” tall) from which rise upright willowy stems bearing dense terminal and axillary racemes (short spikes to 3” long) of slender, long-spurred, tubular blue flowers (each to 1” long) with whitish throats. Flowers bloom in late spring to early summer (up to 10 flowers per flowering stem). Flowering may continue throughout summer into fall if plants do not fall into dormancy. In mild winter climates, plants may return from dormancy in October-November to flower again, but in cold winter climates plants will not be seen again until the following spring.
Species plants were first brought back from China by Pere Armand David in 1865. Plants were rediscovered in 1989 growing in Western Sichuan Province.
Genus name comes from the Greek word korydalis meaning lark in reference to the resemblance of the plant’s floral spurs to the spurs of some larks.
Specific epithet comes from the Latin word flexuosus meaning bending or zigzag.
Problems
No serious insect or disease problems. Susceptible to aphids slugs, snails, rust, and downy mildew.
Uses
Shaded rock gardens or border fronts. Forms a nice ground cover in shady woodland areas. Naturalized areas. A good plant for wall pockets in cool summer climates, but probably not in the St. Louis area.