I mix my own potting soil. 4 parts compost, 2 parts peat, 1 part vermiculite, 1 part sand, and some small amount of lime.. It all goes through a 1/4" wire mesh that I rub into a large tub (to take out any gravel or hard bits) and that I can mix around with a trowel. Then it fills up a trash can and I am ready for the next year.
