Corydalis flexuosa (ht 30 cm), from China, is related to the genus Dicentra, and has lacy leaves and delightful blue flowers comprised of clusters of slender tubes. It has a reputation for being 'difficult' but I have found it grows well in the same area as my Dicentra plants: a shaded, cool, moist position, with humus-rich soil, being woodland plants in their native habitats. My clump has spread quite well over the years. It tends to be dormant for part of the year. There are some cultivars with very intensely blue flowers. There is another Corydalis which grows all too easily in my garden - which I think is C. lutea - with yellow flowers. It blooms earlier in spring and can become a weed, so I don't recommend anyone actually plants that one. The blue version does not become weedy. Corydalis can be grown in pots if a suitable position in the garden cannot be found.