The Secrets of Proper Lawn Fertilization For Cool Season Grasses

Beautiful lawns don’t happen by accident, rather, they are created. One of the secrets to maintaining a beautiful lawn is understanding the basics of fertilization.

The fertility requirements of cool season grass is a little more complicated than it is for warm season grass. Maintaining long term health and beauty of your grass requires at least a basic understanding of the needs of your specific grass type. The right fertilizer applied incorrectly can potentially do more harm than good. Therefore, it is important to know how to fertilize cool season grasses properly.

What are Cool Season Grasses

Cool season grasses, as the name sounds, are venda de grama that thrive best in cooler temperatures. In the U.S., they are found in the central and northern states. In southern states, they are occasionally used to overseed dormant warm season grasses.

The most commonly used cool season grasses are varieties of tall fescue, fine fescue, bluegrass, ryegrass, and bentgrass. These grasses thrive best in temperatures between 65 to 75 degrees. Healthy grass will endure the heat stress of summer much better.

Lawn Fertilization Myths

It is thought that most people fertilize cool season grasses incorrectly. Many believe that since the grass is growing rapidly in the spring, it must be the time when the most fertilizer should be applied. I have heard people say that the faster growth observed after applying nitrogen fertilizer is normal and is to be expected.

No only are these ideas incorrect, but it can lead to the development of grass health issues. Just one of the problems related to excessive nitrogen applied in spring and summer is that it predisposes your grass to disease problems and insect predation.

When it comes to fertilization, when people ask how to fertilize grass, they are usually just asking about the type of fertilizer and how much they should apply. While that’s important, long term results come from understanding why one should apply a certain amount. The answers are found in how cool season grasses grow.

Relationship Between Spring Growth and Fertilization

In early spring, cool season grasses break dormancy and enters into the rapid growth stage. During this stage, these grasses are genetically programmed to use stored carbohydrates that were produced in the fall. Too much nitrogen in spring will force the grass into excessive growth and carbohydrate depletion.

Another problem associated with excessive nitrogen and accelerated growth in spring is a thinning of the cuticle. The cuticle is the outer surface layer of the grass. The cuticle is your lawn’s first defense against disease. A thin cuticle makes it easier for pathogens to penetrate and enter the plant.

Therefore, the goal of spring fertilization is to apply just enough nitrogen to keep the grass functioning properly and to prevent chlorosis. When properly fertilized, the grass will not be pushed to grow faster than it would normally do in spring.

Relationship Between Summer Growth and Fertilization

The approach of summer brings rising temperatures. As the soil and air heats up, cool season grasses will begin to struggle. Grass consumes more energy in summer and should, therefore, be producing more carbohydrates through photosynthesis. However, cool season grass are not as efficient as warm season grasses at fixing carbon. Since carbon fixation is essential in carbohydrate production, warm season grasses excel in the heat, while cool season grasses don’t.

To conserve energy in summer, the natural tendency is for the grass to go dormant. Learning proper watering techniques will help prevent this and allow the grass survive during summer stress. The last thing you want to do is to apply too much nitrogen, especially water soluble nitrogen, that would force growth at a time when the grass doesn’t have the energy to support it. The grass could thin or even die back as a result.

The goal in summer fertilization is to either apply no nitrogen or to provide just enough nitrogen to keep the grass from becoming chlorotic. Organic fertilizers excel at this time. Natural organic fertilizers have slow release nitrogen that is released through microbial activity. It helps maintain healthy populations of soil microbes, while releasing low amounts of nitrogen.

Relationship Between Fall Growth and Fertilization

This is the most important time for cool season grasses. About 75 percent of the total annual nitrogen will be applied in the fall. In fact, the most nitrogen in a single application will be applied after the last mowing of the year. Instead of blade growth, the grass is growing new roots as well as producing and storing carbohydrates. Photosynthesis and carbohydrate production will continue until soil temperatures drop into the low thirties. If the grass doesn’t produce enough carbohydrates at this time of year, it may suffer the following year.


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