fertilize trees once in spring just before they start growing, and again in
fall AFTER they are dormant.You should be using a slow release fertilizer for
this. The ratios on the bag dont matter. In most cases, using balanced
fertlizers under 15-15-15 will add lots of alkaline filler material to the
soil. Other than that, it dosent matter, because plants dont read the labels.
The only thing I would recommend is that you use a balanced fertilizer- one
that has at least some of all the macro nutrients, N, P, and K.

Toad