A good maintenance program involves more than just fertilizing. Maintenance includes things like monitoring and controlling insect, disease and weed problems, mulching around trees, making timely applications of water, and of course fertilizing. Before making any fertilizer applications you should know that fertilizer is not a cure-all.
Fertilizer can increase plant vigor and improve flowering.
However, fertilizer will not solve soil problems stemming from soil compaction, poor drainage, or improper plant installation. Tree and shrub fertilization does not need to be complicated, but your plants will appreciate the application of a little bit of knowledge and a little common sense along with the fertilizer. Fertilizer applications should be based on plant needs. No application is better than an over-application. Try to avoid making fertilizer applications during a drought, as water stressed plants may burn, or die.