|Corydalis buschii surrounding a young Yucca linearifolia|
I first got this corydalis from Janis Ruksans. It was sent to me as these tiny, almost twig like rhizomes, which I was instructed not to let dry out. I planted them and lo and behold, they survived and thrived. Those plants are in another part of my garden and I believe they are still there. These particular plants in the picture I got from Beaver Creek Greenhouses, a rock garden mail order nursery in British Columbia. They have a great list of many rarities and I would highly recommend ordering from them.
Corydalis buschii is touted as a woodland plant, but it is growing in almost full sun in this location and seems to do quite well. The main problem I have with it is weeding in the patch. Since the plant dies down later in the summer, all manner of weeds try to get a foothold on top of it. So when I do this weeding, I am always also digging out the Corydalis buschii rhizomes accidentally. This, fortunately, does not seem to hurt the patch and these dug up rhizomes can be replanted elsewhere in the garden. This plant comes from eastern Russia and Korea and is supposedly hardy to zone 4.
The plant that the corydalis is growing around is a young Yucca linearifolia which I got a couple of years ago from Cistus nursery. You can see what this yucca will look like at maturity here.