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 When to Fertilize Lawns

All turf grasses should be fertilized when they’re actively growing. In Kansas, we can divide turf grasses into two types. Cool season turf, which you see here, is used in many lawns in Kansas. But, we also have warm season turf grasses such as Buffal grass and Bermuda grass.
Let’s start with the cool season grasses first. Most cool season grasses are actively growing during the fall period, and during the spring period. And in Kansas, one of the most popular turf grasses is fescue. If you’re only going to fertilize once during the year, September is the best time to do that.
But most fescue grass will also benefit from another application in October or November. This will help the plant build root reserves to survive the winter, and enable it to green up sooner in the spring.
This method of fertilization in the fall is a good place to start. But for more high quality turf, you may have fertilize a bit more. May is also a good time to fertilize cool season lawns to keep them healthy and strong throughout the summer period.
To reduce the chance of disease pressure impacting our turf grass, it’s usually best to avoid fertilization during periods when the turf can be stressed, or when it’s not actively growing. So fertilizing during the summer is not highly recommended.
Many of the same rules apply to warm season grasses. Warm season grasses include Bermuda grass, Buffalograss, and Zoysia. These grasses are actively growing during the heat of the summer. 
So, the timing difference on these grasses is that they need fertilization during the summer period. Often, these grasses can be fertilized from one to three times during the summer. If you prefer to use one application – June is the best time. However, if you use two applications, you should apply one in May and one in July.
As a precaution, it’s important not to fertilize warm season grasses after August 15th, because this can increase the chance of winter kill injury on the plants.
This feature story prepared with Jason Graves, Kansas State University Research and Extension Horticulture Agent for Central Kansas Extension District. For more information, visit your local county extension office or visit our website at KansasGreenYards.org.