February, March, and April are popular months to fertilize. There's some real confusion about what fertilizers are and why we use them. That confusion comes about because of the terms we use, such as "plant food" and we're "feeding" them.
Instead, fertilizer contains the elements the plants need to make food. Scientists have found there are 13 elements in the soil needed by plants to grown healthy. The elements used in the greatest quantities are nitrogen, phosphorous, and potassium.