Preparing Your Lawn for the Winter (Winterizing)

With the seasons changing and the weather getting cooler a lot of garden centers have been selling a "winterizer" fertilizer that is supposed to prepare the lawn for the low temperatures of winter. Until I worked at a garden center I had never even heard of this special fertilizer and chances are, unless you are an avid gardener you may not have either. Every fertilizer has a unique three number analysis correlated with the letters N (nitrogen), P (phosphoric acid), and K (potash). Other micro-nutrients may be included as well but N,P, and K are considered to be the primary macro-nutrients needed by the plant in larger quantities and they will always be displayed in the fertilizer analysis on the bag. Each nutrient serves the plant in a different way so the analysis may vary depending on plant species, available nutrients in the soil, and time of year.

A winterizing fertilizer should be looked at from two perspectives. That of cool season grasses and warm season grasses. Winterizing means a totally different things for the two. For southern warm season grasses it means trying to encourage root growth with potassium without stimulating new fleshy growth with nitrogen. For cool season grasses it means applying a higher rate of nitrogen in the early fall when the grasses are thriving. Therefore the fertilizer analysis for both will be quite different and caution should be taken to make sure you are buying the right kind for the right climate and type of grass.

A winterizer for cool season grasses might have an analysis similar to this (26-3-12) and could be applied in early to mid October. A warm season grass winterizer should look something like this (5-0-20) and should be applied no later than the end of September but preferably earlier in the month.

In southern lawns if you are following a regimented fertilization schedule throughout the year it may not be necessary to use a winterizer. It might actually just cause nutrients to be leached out of the soil and into the ground water. Because of this, some people think that using a winterizer is just a marketing gimmick and is not really necessary. I would tend to agree. At least if you are fertilizing some during the year. If you have not fertilized at all during the year than I do think that applying a winterizer could be helpful if applied in early September, but wait much longer and it could be a waste or even harmful if it has too much nitrogen.

Helpful Rousources:
Fall/Winter care for cool season grasses
Fall/Winter care for warm season grasses