Fertilize fruit trees in February, hardy fruit trees such as apple, pear, peach and plum. Cherry trees can wait till early spring. Bush and vine borne fruits such as raspberry, blackberry, blueberry and grapes should receive fertilizer in february. A general purpose fertilizer or one designated specifically for fruit trees is best in most cases, follow label directions. Blueberries require fertilizer designated for acid loving plants.
A higher nitrogen ratio, such as 4-1-1 will encourage a lush flush of foliage, but few flowers resulting in less fruit. A low nitrogen such 1-2-1 ratio is better. The nitrogen component should be slow release, half water soluble. Non soluble nitrogen provides nitrogen to the soil over extended periods as it breaks down and releases the componenet gradually over time. The soluble fertilizers break downalmost instantly and give a nitrogen blast to the tree all at once – not good. A rapid spurt may look impressive, but over the long run it is detrimental.
Generally, you would apply fertilizer by scattering the grains evenly around the base of the tree. Try to avoid getting them too near the trunk. Don’t get carried away with excessive fertilizer.
If your tree is located on a sunny site, and the soil is well drained and fertile there’s a chance it may not need much fertilizer at all. The only way to tell for sure is to run a soil test . If the test shows that the soil lacks vital nutrients, you can add them then.
If you’re late and miss the oppoortunity to fertilize, the trees have begun to bloom, you can still fertilize until June.
Ideally deciduous fruit trees [deciduous being those that lose their leaves and go dormant in winter] should be fertilized a maximum 4 times anually. February, May, September or October, or after you have harvested all fruit from the tree. Don’t fertilize in late summer or early fall, new growth encouraged by the fertilizer application is easily damaged by even a light frost. Damaged foliage leads to disease which can easily spread beyond the new growth. Suggestions as to timing of fertilizer applications are variable depending on your micro-climate and the gardener is encouraged to use common sense and dilligence in researching individual regional variations.