Karl, there is no one medium that is the "best" medium. The correct answer to your question is it all depends, It all depends on the location's year around temperature, height of the container, size of the tree. It is more about ingredient size, how they fit together in a blend, how much water the ingredients will hold while still supplying adequate oxygen. One popular, and often used nursery mix is 3 parts conifer bark, 1 part good Canadian peat moss, and 1 part coarse sand. The problem with this medium is that you need to transplant using new ingredients every year. In the colder climate of Colorado I use 3 parts half inch CHC and 1 part peat moss. I don't think that would be the best for a tree in Scottsdale's hot temperatures. Maybe something like 3 parts CHC (made up of 1-1/2 parts half-inch CHC chips and 1-1/2 parts 1/4 inch CHC chips.), plus one part good Canadian peat moss and *perhaps* 1 part coarse sand). A medium in your area would need to have a high water storage capacity, while still providing good air filled porosity. Send me a private message with your address, and I will send you some excellent reading on what the requirements of a good medium are and why. My advice is read it a minimum of two times and then you can make some knowledgeable decisions. - Millet
