What is fertiliser and why is it used?

Fall, spring or summer are times when trees can be fertilized.

Specifically, trees are not as needy as edible and ornamental plants for regular fertilizing schedules. But for those who seek fertilizing guidelines, trees benefit from summer fertilizer treatments when they are newly established, recovering from pests, or young or when there is environmental stress, such as prolonged drought. Fall is an effective time for fertilizing when the tree will not flower, fruit or seed until after new spring growth. Spring may be an effective time when the tree flowers before new spring growth.