While most manufacturers and lawn care companies say that you need to fertilize your lawn up to five times a year, in reality you only have to do this up to three times in a year. Instead of the frequency of your application of fertilizer, you should look more into the formulation of the fertilizer in terms of how much nitrogen, phosphorus, and potassium a certain blend contains. The composition or type of fertilizer you use will also depend on whether it is spring, summer, or fall.
Generally speaking, those living in the northern hemisphere depend on when the snow will melt for lawn fertilizing. This is usually done during the months of April to early May. Those whose lawns that had a crabgrass problem during the previous summer may add a crabgrass preventer with the fertilizer. If crabgrass has already grown, dig out the crabgrass clumps or use a blend of fertilizer and weed control instead.
Read more on lawn fertilizing.