KC Gardens

Here’s why you should fertilize your bluegrass and tall fescue lawns in September

Fertilizers containing higher concentrations of nitrogen are ideal. Examples of fertilizers to apply in the fall would be 30-0-0, 29-0-4 or 30-0-4 or 25-0-0.
Fertilizers containing higher concentrations of nitrogen are ideal. Examples of fertilizers to apply in the fall would be 30-0-0, 29-0-4 or 30-0-4 or 25-0-0. Johnson County K-State Research & Extension

After a summer of growing, it is now feeding time for hungry bluegrass and tall fescue lawns.

Growing grass is all about developing strong roots, which results in the lush green carpet look. Fertilizing lawns in September builds strong roots and crowns and is essential for success.

Choosing the right type of fertilizer is important. Nitrogen fertilizer, the most important nutrient, is needed and used in the greatest quantities. It is essential for healthy growth, color and density.

Vigorously growing lawns use more than is typically available in the soil so it must be replenished.

Nitrogen, the first number listed on a bag of fertilizer, helps thicken the stand and encourages a strong root system. Cooler temperatures, rainy days and the addition of the nutrients builds a foundation for a healthy lawn without excessive top growth. This results in a green lawn with less mowing.

November is the next most important time to fertilize. This application is applied around the final mowing, normally mid-month. It enables the lawn to green up earlier in the spring, without excessive shoot growth often accompanying early spring applications.

Phosphorus, the second number listed on the bag, is needed for the growth of roots and shoots. Adequate quantities are typically present in the soils.

Potassium, the third number, is essential for the overall health, stress resistance and cold hardiness. Like phosphorus, it usually is found naturally in soils.

Applications of fertilizers containing phosphorus and potassium are not recommended unless a soil test indicates the need. A starter-type fertilizer, one higher in phosphorus, is applied when overseeding to encourage quick establishment of the new seed.

Based on the need of the grass and our local soils, fertilizers containing higher concentrations of nitrogen are ideal.

Fertilizers will always have three numbers displayed. The numbers stand for the percentage of nitrogen, phosphorus and potassium contained in the bag. Examples of fertilizers to apply in the fall would be 30-0-0, 29-0-4 or 30-0-4 or 25-0-0.

This emphasis on fall fertilization may conflict with some that promote spring applications.

Cool-season lawns experience a flush of shoot growth in the spring. Applying fertilizer before this flush is over causes the grass to grow quickly. The rapid growth exhausts the plant’s food reserves. The result is excessive top growth, which means you mow more and increase stress heading into summer.

Spring fertilization, if at all, is best done in early May after the initial spring flush.

Fertilizer must be watered into the soil to activate. Do your part for clean water. Sweep or blow fertilizer pellets back onto the lawn. Pellets that land on hard surfaces quickly wash into our water supply leading to impaired water.

Don’t let the dinner bell go unanswered. A healthy serving of fertilizer is the recipe for success.

Dennis Patton is a horticulture agent with Kansas State University Research and Extension. Got a question for him or other university extension experts? Email them to garden.help@jocogov.org.

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