The traditional time to fertilize gardens is in early spring. At or around your expected first frost-free date is a good time to apply a general fertilizer. We recommend organic fertilizers, such as composted manures, bone meal, fish emulsions and alfalfa meal. Plants that are heavy feeders, e.g. most vegetables, roses and annuals, should be fed throughout the growing season. Slow-release granular fertilzers can be used. Applying about 1 inch of compost to the soil every year will largely eliminate the need for other fertilizers except for heavy feeders.

This article was written for Oregon gardeners but it is a useful source of information on fertilizers.

Courtesy of NYBG Plant Information