The Osmocote works when the plants need it so when the soil warms up and the plants put on fast growth the Osmocote will kick in. Most likely once your day temps are above 70 degrees. Unlike Miracle Grow it keeps releasing nutrients slowly for months but does not give that swift kick in for rapid growth. The advantage is that slow and consistent growth is less tender and less subject to disease and insects. I would not use any fertilizer on trees unless there is some condition that warrants this. Trees have an extensive root system and grow best at their own pace. Keep growing, Marianne Binetti