| They may be refering to an open mix, like medium bark or some of the other chunky mixes. I, on the other hand have been growing in a closed mix for the last 15 or 20 years. It is 3 parts small perlite to 2 parts Canadian peat. I call it a closed mix because bush snails and mealie bugs can not move around in it, and I do not have nearly incurable problems with these critters as some do. Cynthia |