I forgot to add that in general I add a one third part dried and crushed red clay (I find that old red clay building bricks that are disintegrating work very well) and half a part vermiculite to the mix. This then becomes my standard mix for all my plants. All measurements are by volume.
It's very important to place a layer of pure sand over the top of the growing medium when potted up. Not only does this prevent the organic matter and vermiculite from floating to the top but also creates a barrier that prevents the medium from drying out too quickly.
It's very important to place a layer of pure sand over the top of the growing medium when potted up. Not only does this prevent the organic matter and vermiculite from floating to the top but also creates a barrier that prevents the medium from drying out too quickly.