Garden stores and departments offer numerous brands and types of fertilizers. Gardeners have been trained to think that each type of plant needs its own fertilizer. Since our soils contain a significant amount of phosphorus and potassium, I have found that lawn fertilizers, which are high in nitrogen, work very well for most trees, shrubs and flowers. The only things I use any other fertilizers for are containers and fruiting vegetables, especially tomatoes. General purpose fertilizers with a 1-1-1 balance of nitrogen, phosphorus and potassium, or vegetable fertilizers with a 1-2-1 balance are better for fruiting vegetables. Typical offerings are 16-16-16 or 5-10-5. For containers I use a coated fertilizer which releases gradually every time plants are watered.
Lawn fertilizers with part of the nitrogen in a slow release form are best for spring application. They will last much longer into the summer. I also like to see micro-nutrients such as iron and zinc included in mixed fertilizers. Organic fertilizers naturally contain all the micro-nutrient elements.