There are six macronutrients and seven micronutrients. It is important to stress that most gardeners need only concern themselves with supplying quality pre-packaged fertilizers according to manufacturers instructions. These are the nutrients that you will see commonly identified on the fertilizer bag or box. Nitrogen promotes healthy green growth. Phosphorous is vital to strong root growth and flower production.
Potassium is needed for vigorous growth.
Fertilizers formulated for strong green growth will have a larger percentage of nitrogen. In general, stay away from high nitrogen content fertilizers for use with roses. The secondary macronutrients are sulphur , calcium , and magnesium . Use of a high quality rose fertilizer will ensure that these macronutrients are made available to the roses. Of these secondary macronutrients, magnesium is of substantial interest to the rose gardener.