There is actually a difference between trees growing in the forest and trees placed in a landscape because trees in the forest can be naturally fertilized. Fallen, decaying leaves and dead branches create natural fertilizer. The trees around your property tend to need a more direct method of fertilization. When you fertilize, it will help the tree to grow to full size, live longer and be more aesthetically pleasing.
Fertilizer is any natural or chemical substance that is added to soil to increase the nutrient content of the soil. Nutrients can come in two groups – micro- and macronutrients. A trained professional will know what your tree needs based on its current nutrient levels, and the timeframe for fertilizing that tree will depend on its age. A tree at any age may be getting acceptable nutrients from the soil already, but the quality of your soil is mostly determined by your region and current plant care if any.