What Temperature Is Right to Put Fertilizer for Winter Out?

The Right Temperature

• When the temperatures begin to reach below 50 degrees Fahrenheit at night, it's time to pull out the winter fertilizer. The extra nitrogen in the winter fertilizer can help the lawn stay strong during the cold winter months. Colorado State University Extension recommends applying the fertilizer to the ground about two weeks before the ground begins to freeze and while the grass is still green. There's no harm in applying winter fertilizer to the ground before that time, though.

The Right Time

• When winter gets a late start, consider applying the winter fertilizer toward the middle of October or the beginning of November. When cold nights come early in the year, begin your application in September. It all depends on the temperature your lawn is exposed to. Watch the weather reports and be ready to apply the fertilizer when the temperature starts to dip. You can cut your grass before using the fertilizer so that it gets the best possible ground cover.

Winter Fertilizer Brand Directions

• Before using your winter fertilizer, read the directions on the bag. Each brand may have its own suggested temperature range that you should follow when using the fertilizer. Different fertilizer brands also have different levels of nitrogen in them. According to Colorado State University, nitrogen is the most important component of a winter fertilizer. Winter fertilizer with a nitrogen ratio that is five times that of the phosphorus and potassium, such as a 25-5-5, will work to winterize your cool-season turf, but you can find higher ratios, too. Some winter fertilizers have a 32-0-10 ratio. Look for one that uses a slow-release nitrogen that can help your grass grow long after the actual application. For warm-season grasses, look for fertilizer with lower nitrogen and higher potassium, such as 5-5-25.

Performing Two Applications

• Some winter fertilizer brands recommend doing two applications. Ultimately, it's up to you whether you want to fertilize twice, but it can help the roots of your plants stay healthy. Do one application in late August or early September and another in October. If the temperature stays high longer, you can safely wait to do the second application.