Fertilizer bags are marked with 3 numbers, Nitrogen (N), Phosphate (P), and Potassium (P). 2.3.2 is a balanced fertilizer which is used when planting all plants to give them an initial boost. 3.1.5 is high in Potassium and this stimulates flower development. 5.1.5 is high in Nitrogen and Potassium and is used to fertilize lawns.