Corydalis flexuosa was a great introduction in the 1990s, and it has also given rise to several excellent hybrids. They are all plants with delicate foliage growing through the winter, after a dormant season in late summer. Then in spring the stems are topped with the distinctive blue flowers, over a long flowering period. Each will soon form a good patch, which can be split to provide a lovely ground cover between shrubs.

Corydalis 'Korn's Purple' is an excellent variety from Sweden. The flowers come in clusters of many individuals, and range from dark purple to metallic blue, with a white centre. Bulks up well.