DON'T FERTILIZE MAST TREES IN FALL. Each spring, a selected group of trees should be fertilized. Begin by raking the debris from the base to the drip line. Then apply a medium dosage of 10-10-10 to 15-15-15, slow release fertilizer. Begin a couple feet from the base, it should be spread evenly around the entire tree and out to the drip line. In northern settings, fertilizing in late summer or fall can actually do more harm than good. This burst of fertility can prompt trees to spur new growth too late into the fall. The result can be frost damage to this tender growth and provide unnecessary stress. (quoted from Steve Bartylla-Habitat Improvement Vol. #3)