Fertilizer Numbers: How To Read The Numbers On Fertilizer Bags

To get the most from your “plant food” dollar, keep clearly in mind why you are fertilizing. Each fertilizer has a definite purpose.

The one you should use depends upon:

  • Your soil
  • The plants you grow
  • The results you expect

fertilizer numbers

Is your soil friable (easily crumbled) or hard packed? Acid or alkali? Are you cultivating the plant for its leaves, flowers, or roots?

Do you want quick action from the plant food for a short time, or slow action for a long time? These are the things to consider in selecting a fertilizer.

A wrong fertilizer choice is not only a waste of effort and money, but can actually be worse than no fertilizer at all!

For growth all plants require:

  • Nitrogen – to stimulate the growth of foliage
  • Phosphoric acid –  to encourage the development of fruit and flowers
  • Potash – to stimulate the growth of roots
  • plus minute amounts of trace minerals

Nitrogen is the most quickly used up and, therefore, the one that must be replaced most often.

Different Plants Use Different Types Of Fertilizers

A so-called “complete fertilizer” is one which contains all three of these nutrients. Since different types of plants require different amounts of each food, however, no one fertilizer is “complete” for all plants.

The fertilizer that makes your lawn grass thrive may cause the tomatoes to go to foliage.

The one that makes the wisteria bloom may cause the caladium to wear itself out producing unwanted flowers instead of fancy leaves.

The fertilizer that is correct for the fragrant-leaved geranium whose flowers are unimportant is wrong for the zonal geranium from which you expect blossoms.

If you are growing leafy plants such as lettuce, ivy, or grass, select a fertilizer high in nitrogen.

If you are growing fruit or flower plants – tomatoes, roses, strawberries, candytuft – use a fertilizer high in phosphoric acid.

For root crops such as potatoes, carrots, and beets, look for a high potash content.

Two Fertilizer Groups – Chemical and Organic Plant Food

Fertilizers are divided into two groups – chemical and organic. Each group has advantages and disadvantages.

Chemical Fertilizers

Chemical fertilizers are quick acting and cheap. In addition they are made according to a definite formula.

When you buy one you know exactly the percentage of nitrogen, phosphoric acid, and potash in each bag and whether or not it contains trace minerals.

Under the trade name on each fertilizer bag or bottle will be three numbers, for instance, 5-10-5.

The first number indicates the percentage of nitrogen, the second of phosphoric acid, and the third of potash.

Thus, you can easily select a fertilizer that is high in whatever your plant particularly needs.

For a potato patch you may select the formula 5-8-7; for celery, 8-4-4; for roses, 4-12-4; for tomatoes 4-6-6. A general all-around mixture is 5-10-5. The base of a chemical fertilizer is usually sand.

Chemical fertilizers must be applied strictly according to the directions on the sack. An overdose can burn a lawn or plant or even cause it to die.

A teacup holds about one-half a pound of fertilizer. Always water fertilizer in thoroughly, and never let it touch the foliage or stems.

Chemical fertilizers use up the humus in the soil. They are short lasting and often leave a residue in the soil that causes an acid or alkali reaction.

Therefore, you should not use the same chemical mixture on the soil year after year. You must also add large quantities of humus to replace that which is lost.

Organic fertilizer is slow acting, long lasting, and build up the soil over a long period of time.

Because of their slow action, they may be used more freely with less danger of overfertilizing.

Any fertilizer can be overused, however. Every plant has a saturation point beyond which more fertilizer is bad.

The plants seems to be affected by too much fertilizer as human beings are by too rich a diet. Remember, too, that some plants such as nasturtiums and certain herbs actually prefer a rather poor soil.

A good rule of thumb in choosing between a chemical and an organic fertilizer is this: If you are primarily interested in the crop that year – annual flowers, tomatoes, etc. – use chemical.

If you are more interested in long term growth as in the case of shrubs, long-lasting bulbs, and perennials, then use organic.