Wait until the leaves have grown to about half their normal size before you apply fertilizer containing nitrogen (the first number on a fertilizer package). The tree will be able to use the fertilizer better when it has more foliage. Do not give your tree too much fertilizer. Most ornamental trees do not need much nitrogen fertilizer for good growth. Applying too much can produce excessive, lush growth and make trees more attractive to aphids and other pests.
If you use a soluble chemical fertilizer, scatter it lightly on the soil under the tree's dripline (at the edge of the branches), then water well to dissolve the fertilizer and carry it into the soil. . Do not apply chemical fertilizer or manure close to the trunk, since this may injure the tree. Organic fertilizers like blood meal (13% nitrogen) do not dissolve in water but release their nutrients gradually as they decompose.
By V. Lazaneo, Urban Horticulture Advisor, Emeritus, UC Cooperative Extension, August 2012