Hi, Well you don't say what kind of plants you are planning to fertilize. However, for me, I generally prefer to fertilize most of my garden in the early spring, just as the plants are breaking dormancy or just before I set out annuals or vegetables. I do add organic matter like rotted manure and compost all through the growing season, but if I'm using commercial fertilizer I prefer a slow-release, granular fertilizer that will keep the plants fed all season long. You can buy slow-release products at any garden center. Just follow label directions.