These plants started blooming in late May and are still going strong on the last day of October. Perennial Yellow Corydalis has staying power.
In 2008 when I declared this plant a Garden Winner I wrote:
“Corydalis self-seeds (the seeds have a substance that attracts ants and they carry them around, spreading the plant) but the seedlings grow very loosely in the soil and are easy to control.
About a year after I put my first plant in the ground, I was weeding nearby and caught a whiff of the most delightful scent. It turns out that the flowers are pleasantly fragrant. I always kneel down to inhale the sweet scent when I’m walking by.
I grow corydalis in the problem areas of my garden because the plant blooms so profusely, is pest and disease-free and really livens up the shade.“
I haven’t had to add any plants to my yard since then because they do indeed self-seed (in a friendly way, not in a tear-out-your-hair-because-this-is-worse-than-Vinca-Minor way).
“Yellow corydalis is an unusual perennial in that it grows well in full sun or full shade (in the shade the plant may stay a little smaller). It grows in zones 3-8 and appreciates moist, well-drained soil.
Corydalis has ferny foliage that adds interest to the garden even when the plant isn’t blooming, but that’s not often because corydalis blooms from May through October. It grows 12 to 15 inches tall in a mound with beautiful gold flowers.”
Fourteen years later Yellow Corydalis is still a Garden Winner.