Hi,
I am looking to repot some Japanese maples into Gritty Mix. They are currently in a 1:1:1 mix of pine bark fines (unscreened, only largest pieces removed), MiracleGro potting mix, and Permatil. I've been successfully using this mix for 6-7 years, though it's probably worked well for me because I've also potted up, root pruned, and refreshed the soil every couple of years. I purchased the trees online at the Size 1 and they now need the largest size pots I can manage/afford.

So, I am still hunting for the right size bark, but I have tracked down crushed granite (Gran-i-grit) and Turface and have both. However I am looking at needing to screen major amounts of Turface...going to start tomorrow, but I wanted to check to see if I could use Permatil as a sub. Permatil particle size is close to that of Gran-i-grit and uniform. From the PermaTill website:

PermaTill expanded slate characteristics include:
Sterile and Inert
Durable; High Compressive Strength
Particles contain 50% available porous surface area
26.9 me/100g CEC for enhanced nutrient retention
6 - 10 % moisture retentive
High water release curve allows for root uptake and movement through the soil
http://www.permatill.com/home-garden-products.php?cat=8

I am particularly wondering how the 6-10% moisture retention compares to Turface.

Thanks for any help
Deanna