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Do You Need To Fertilize This Fall?

The simple answer is yes if you had to fertilize last fall and/or this spring. If you don’t have to fertilize on a regular basis, you probably won’t have to this fall, either.

The job of fertilizing is, arguably, one of the most misunderstood aspects of horticulture, and it isn’t helped by those who refer to fertilization as plant feeding. The late plant physiologist, Dr. Alex Shigo, explained in his writing and during his speaking engagements that plants don’t have to be fed. They make their own food through photosynthesis.

Why fertilize then? Fertilization actually “feeds” the soil. It replenishes nutrients that occur naturally in good soil. Fertilization can be compared more accurately to taking vitamin supplements than eating food.

Soil is moved around and mixed with subsoil during residential construction, resulting in inferior soil. When topsoil is removed, the nutritional elements available for plants are only those present in the subsoil. When topsoil is mixed with subsoil, this, too, greatly reduces the nutrients available to plants.

Once nutrient-bearing soil is removed from a piece of property, it’s gone forever. This means it has to be replenished constantly to grow healthy plants. Plants need a number of nutrients for good health, just as we do. The main elements plants require are nitrogen (N), phosphorous (P) and potassium (K). Also necessary but in lesser quantities, is a group of secondary nutrients that includes calcium (Ca), magnesium (Mg) and sulfur (S), and a group of micronutrients that includes boron (B), copper (Cu), iron (Fe), chlorine (Cl), manganese (Mn), molybdenum (Mo), and zinc (Z). Non-mineral elements hydrogen (H), oxygen (O) and carbon (C) are also needed but they come from the air and water rather than the soil.

Besides their presence in soil, essential nutrients have to be in a form that will dissolve in water, which is how plants absorb them. The best way to know if your soil is deficient in any of the essential nutrients is with a soil test. You can buy very basic soil test kits at garden stores but a more comprehensive, reliable test is best left to our plant health care professionals. They’ll take soil samples from your yard and send them to a lab for analysis. When they get the results, they’ll present you with recommendations specifically for the soil conditions in your landscape.

We follow industry standards that advise us to fertilize only to meet specific objectives. The most common objective is to replenish specific nutrients. In some cases, objectives may be more exotic, such as acidifying basic soil to grow acid loving plants like azaleas and rhododendrons.

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