The best advice is to follow the recommendations on the Osmocote fertilizer package. The usual rate is 3 tablespoons for a 2 gallon container so you could just double that to six tablespoons then add one more tablespoon to make a total of 7 tablespoons for your 5 gallon containers. Work the fertilizer into the top one to three inches of the soil. Sometimes the fertilizer package will say \"one capful per 2 gallon pot or 4 sq feet\" but one capful equals 3 tablespoons as is explained in the fine print under the directions. I am impressed at your effort to use exactly the right amount of fertilizer. Although you won\'t harm your plants using just a little too much or not enough plants for optimum growth all gardeners should try and use the dose recommended on the fertilizer label. Keep growing, Marianne Binetti