By the numbers: Different fertilizer combinations affect how plants grow

A common conversation with a vegetable gardener goes like this: "I planted tomatoes last year in my garden. They grew to be 6 feet tall. The plants looked healthy, but I only got a few tomatoes. What happened?"

My response to the gardener is another question: "What kind of fertilizer did you use?"

The answer varies from manure, to 12-12-12, to a commonly used liquid 20-20-20.

So what is really going on? Plants respond to different fertilizers in different ways. You can tell a plant how to grow by giving it different fertilizer combinations.

For example, if you fertilize a plant with a fertilizer higher in nitrogen (the first number) than in phosphorous (the second number), it will have a tendency to produce shoots and leaves at the expense of fruits and roots. If you use a fertilizer that has a middle number higher than the first number, the plant will put more energy into producing roots and fruits.

With this in mind, I would suggest you fertilize your vegetable garden with something like an 11-15-11. As you can see, the nitrogen level (11) is lower than the phosphorous level (15). As indicated above this combination will tell the vegetable plant to produce roots and fruits instead of shoots and leaves.

When transplanting plants such as tomatoes, peppers, cabbage, etc., it is important to water them in with a high phosphorous fertilizer such as a 9-59-8. The extremely high phosphorous level will encourage the transplants to produce roots, exactly what they need to do in order to survive the transplanting process.

Although I have written about vegetable plants, the same kind of thinking is important when you transplant trees, shrubs and perennials. Make sure that during the transplanting process you use a high phosphorous fertilizer.

After transplanting, the kind of fertilizer that you use will depend upon what kind of plants you are growing. If you are growing shade trees, then use a fertilizer that is higher in nitrogen than in phosphorous. You want your tree to produce shoots and leaves. After all that is what you plant a shade tree for.

If you grow perennials because you want them to flower, use a fertilizer with a middle number higher than the first number. This combination will encourage the perennials to flower profusely.

When you go to a garden center, you will find all kinds of fertilizer combinations on the shelf. Just keep in mind the ratios of nitrogen to phosphorous and you will be able to select the right combination for the plants you are working with.

Send your gardening and landscape questions to Paul Schnare at P.O. Box 699, Cape Girardeau, MO 63702-0699 or by email to news@semissourian.com.