Here i grow them in my heavy clay, as in the wild. I think there's a legend about the fact they need a lot of drainage.
In nature they grow in a rich humus and calcareous clayish soil, most often in cold and wet ravines where drainage is quite limited but free flowing during heavy rains.
The first 5-8cm layer is composed of leaves compost and then deeper really heavy clay with very few rounded rock chips.
Beeches like clay, Cypripedium like beeches.
However they're not bog/standing water plants.
To resume nose buds in humus, roots in clay.