In traditional lawn care circles, a “winterizer” is a late season application of nitrogen based fertilizer on a cool season lawn. Usually this is done sometime before thanksgiving.
Lawn care pros often push this type of application. The idea that the plant will not use the nitrogen until next spring, when it emerges from dormancy and finally uses the carbohydrate reserves. In theory, this heavy dose of Nitrogen gives the lawn a boost heading into the growing season.
It seems fairly straightforward, but it’s not exactly healthy for your lawn. Put in human terms, this is the equivalent of trying to eat a double cheeseburger right before bedtime.
Just like you wouldn’t feel good the next morning, it doesn’t help your lawn going into next spring.
For starters, your lawn does not actually see the benefit of those nutrients. Any application you put down in late November is going to be about 12% as efficient as it would have been in September, when the lawn is actively growing. And that's only if it gets absorbed. In reality, most of the fertilizer does not end up getting into the root system of the plant. Instead, the fertilizer usually runs off into watersheds over the course of the winter before your lawn can even get the chance to break it down and use it. This happens because the ground is often highly saturated with water in the winter, causing the fertilizer to simply float away before it breaks down.
When the fertilizer floats away due to precipitation (in the form of snow, rain, or sleet) it’s going to end up in the nearest body of water. This is where things start to go wrong, because traditional synthetic “winterizer” applications are often very high in nitrogen (some are as high as 50% Nitrogen). This is the very thing that will cause regulatory agencies in your state and/or municipality to take corrective action and crack down on pollution. In fact, many states have already banned nitrogen applications in the winter because of this practice. Look no further than the state of Florida, where an increasing number of counties banned the use of Nitrogen applications starting in 2009.
Lawn care companies usually push Winterizer not because it’s beneficial to your lawn or the environment, but because it's an opportunity to move product during an otherwise slow lawncare season.
Don’t fall for it. Your lawn - and the environment - will be much better off!