Some of my best plantings are not my doing. My role, in these cases, has been to recognize the plants’ qualities and then leave well enough alone. Those pastel-pink columbines that look so pretty in front of the dark green leaves and flaming red flowers of my trumpet honeysuckle vine? I planted the honeysuckle, but the columbines just appeared one year and have remained.
A few years back, I almost pulled out what I thought might be a weed growing in front of some yews near the east side of my house. Luckily, I stuck to my philosophy of not removing any “weed” unless I knew it was a weed.
This “weed” grew into a neat mound of slightly bluish leaves, each one small, lobed and grouped in threes at the ends of long stalks. The whole effect was very dainty, something like a combination of maidenhair fern and columbine in a compact mound 18 inches high and wide.
But this plant was more than just pretty leaves. The ends of the stalks were capped by clusters of yellow flowers sized just right to the mound of greenery and the individual leaves that create it. In shape, the flowers resembled snapdragons. The very best thing about this plant, though, was the way the foliage and the blooms looked as exuberant in late summer as they did in spring, when the show began.
So what was this plant?
With the yellow flowers and the shape and color of the leaves, the plant could have been mistaken for some kind of rue. But the leaves lacked that distinctive, strong rue aroma. The plant was — drum roll, please — yellow corydalis (Corydalis lutea), and it kept on blooming and looking fresh into autumn.
I had no idea how the plant got where it is, but the location was evidently to its liking. Corydalis abhors high summer heat, but otherwise enjoys full sun or part shade and soil that is well-drained all year. That east-facing bed near my house gets cool morning sun and is shaded from hot afternoon sun. The soil there is gravelly and raised, so it drains well, and a leafy mulch locks in moisture.
Rock gardens and crevices in stone walls suit this plant perfectly, as long as they are protected from hot sun. The plant has no pest problems worth mentioning.
My one mound, pretty as it was, looked lonely, however, so I wanted more plants. Corydalis is not an especially easy plant to propagate.
Freshly collected seed can be sown without any treatment, but purchased or old seed needs a period of moisture and warm temperatures followed by a period of moisture and cool temperatures before it will sprout. (Alternatively, seeds can just be planted outdoors in summer, to sprout the following spring.) The plants are not very amenable to being divided or, unless they are small, even being moved.
Despite being finicky when grown from seed by gardeners, corydalis self-seeds quite readily where conditions are to its liking. My original plant has multiplied with abandon, young plants insinuating themselves into crevices in the nearby stone wall and in cracks in the concrete of my front stoop.
In Great Britain, where growing conditions for corydalis are ideal, corydalis is much more fecund and is often considered a weed. Here, excess plants are not overly abundant and are easy to pull out of the ground. I remove some and leave others for their all-season-long show.