Mycorrhizal fungi is a natural organic additive that will give a powerful health boost to your trees. This naturally occurring fungi forms a symbiotic relationship with most tree and plant roots growing in native woodlands. Mycorrhizal fungi helps plants exchange nutrients and moisture which can significantly reduce loss and decline of trees due to poor soil conditions and drought. It is not 100% necessary to make your tree survive, but considering most urban areas and home sites are deficient of this beneficial fungi, it would provide an enormous enhancement for your tree's survival, overall health and growth rate. (Apply one ounce of mycorrhizal fungi per tree for best results. Trees with a caliper of 1 inch or more require 3 ounces per tree.)