Creating a bed for planting dicentra
I recently bought a couple of dicentra plants to put in a small previously unused bed that is right next to my house in my back garden. However when I dug the hole to plant them in, I found the layer of soil to be quite shallow, about 15cm, under which is a 25cm layer of grey shale like substance, and under that is clay! I'm assuming that the 2 plants would not survive being planted in this environment.
I wondered if I dug out enough of this bed, say 60cm deep x 30cm x 30cm for each plant, and filled it with top soil and potting compost, would that be a suitable environment for my two dicentra plants?
Any advice would be much appreciated.