The custom recipe we order from Tank's Green Stuff to germinate and transplant nursery plants with is equal parts cinder sand, compost, and perlite. We've been loving this well draining mix and finally have made it available for only $5 a 20lbs bag after so many inquiries. We reuse birdseed bags (Patagonia has a large amount of birdseed bags going to the landfill every day) to fill with potting soil, that our volunteers generously donate. We don't ship potting soil, but sell it at the nursery and you can order it for pickup or drop off orders as well. Happy propagating!