Are you going for 'cryptic question of the week'?

It needs to be well drained, therefore most garden soils will do with lots of grit added. I don't know what your soil is like, Mdarcy, but if I am building a new rockery bed I would use two barrowloads of my garden soil and mix it with one barrow of grit and one barrow of soil conditioner. If I am growing in a pot or trough then it would be one portion of each.

I do the same as Bb. The grit I use is 5mmm stuff and the soil conditioner either composted bark or non peat potting compost.