I used to mix 2/3 perfect loam soil and 1/3 potting mix for my dad's container tomatoes. Last year I mixed some clay soil with potting mix (1:5 - 1:10 ratios depending) for all my pots including houseplants. I have had *much* better luck with this mix than with straight potting mix of any variety. Works better than using the water absorbing gel polymers, too. Liz