If by "adding these balls" you mean sprinkling the Osmocote fertilizer into the soil, then the answer is you only need to do it once every 6 to 9 months. The fertilizer is released very slowly when the plants need it so most gardeners use Osmocote in the spring and it feeds right up until the end of summer. Just be sure you apply the correct amount. Each package of Osmocote will supply the suggested amount of product to use depending on the size of the area you are fertilizing or the size of the  container if you are growing things in pots. Keep growing, Marianne Binetti  P.S.  The round granules of Osmocote do look like little balls.