You could try it, but don't use your good trees!
Unfortunately that stuff swells up so much when it is hydrated and then shrinks back down so much it will leave voids behind in your soil. Maybe if it were ground finer. I had some mixed (unbeknownst to me) in a mycorrhizae product and it was like someone had spilled ice all over my trees.
Maybe it would be okay on the surface of the soil. In the mix I think there would be too much displacement.
http://forum.bonsaitalk.com/showthr...d=8125#post8125
Regards,
Matt