What do the three numbers mean on fertilizer bags?

Have you ever wondered what that three-digit number on the front of fertilizer bags means? It represents the three main fertilizer nutrients (nitrogen: N, phosphorus: P and potassium: K). They are always listed in the same order to make up a three-digit formula: N-P-K.

Each of these three nutrients is designated by a number — a percentage of the pounds of each per hundred pounds of fertilizer. For example, a 20-10-5 formulation means there are 20 lbs. of nitrogen per hundred pounds of fertilizer, 10 lbs. of phosphoric acid and 5 lbs. of potassium.

When you select a fertilizer, remember the purpose of each ingredient and relate the percentages to the needs of your plants and/or lawn.

  • Choose fertilizer with the highest first number for fast-growing grass.
  • Choose fertilizer with the highest middle number for good flower and vegetable production.
  • Choose fertilizer with the highest last number to toughen your plants against disease and winter′s cold.