Corydalis ochroleuca

Not many shade-loving perennials bloom all season.  Two exceptions are the estimable Corydalis lutea and this, essentially its white-flowered, yellow-snouted sibling.  It's considerably rarer than its all-yellow relative, and also somewhat shyer in its self-sowing.  Your gardening buds will be begging for whatever volunteers occur, because it's one of the most desirable perennials for shade.  It's now known to botanists as Pseudofumaria alba, but that name may take a while to take hold in gardening circles.

Part shade to sun; well-drained humus-rich soil; 10"x12"; spring to fall; Zone 5

Propagated from seed; deep 3.5-inch pots