Many of us have seen a ferny plant with tiny yellow flowers growing on walls and in cottage gardens in England, where it self-sows enthusiastically. This plant is Corydalis (kor RID ah liss), and it grows from rhizomes. It resembles the habit and form of Bleeding Heart, and it likes similar growing conditions. It has delicate lacy-looking foliage and racemes of spurred flowers in the spring.
There are about 300 species of Corydalis, both perennial and biennial, belonging to the poppy family. Give these plants full sun to partial shade where summers are not too hot and well-drained soil with regular moisture.
Most of the species resent being transplanted, but they can be divided in spring or fall if watered well to smooth the transition. However, they grow best where they self sow, and they seem to find very pleasing sites for themselves. For example, they have self sown at the edge of stone steps in my garden and look charming there despite the fact that there seems to be little dirt to nourish them.
There are blue-flowered varieties now available, but I have not been able to get them established in my own Midwest garden. The yellow ones, such as Corydalis ‘lutea’, bloom well over a long season, however, and their blue-green foliage is attractive all of the growing season.