Substituting granite in gritty mix
I've had very good success using the 5:1:1 mix for raised planters and a variation of the gritty mix in my small containers. I recently acquired a reasonably large Japanese maple (7-10 gal) and I'm reluctant to use the straight gritty mix for the re-pot. I'd like to substitute the granite portion and I'm looking for advice. In a older post, Al suggested that the pine bark has drainage/water retention properties which approximates an average between the Turface and granite. With that in mind could I simply leave out the granite and increase the % of pine bark or would I need to add perlite or something similar to maintain adequate drainage.
My reasoning is this: the native soil on our property is pure sand and, when it comes time to recycle the mix, I don't want to add granite to my garden beds. I've considered using the 5:1:1 (this won't be the permanent home for the maple) but I really like the qualities of Turface. My sandy (very low CEC) raised beds can't get enough of it.
Thanks in advance!