It’s been a rough summer, but feeding in fall will help your lawn thrive in spring
Each September, I recall the famous line from “Little Shop of Horrors”:
“Feed me Seymour!”
Just like this monstrous plant needed to be fed, so do our lawns. Cool-season lawns with bluegrass and tall fescue are starving for food and requiring fertilization.
A September application of fertilizer helps the lawn recover from summer stress. This fall application jump starts the grass for spring growth, resulting in a thicker cover and fewer weeds. The most essential nutrient needed to help build a healthy, thick lawn is nitrogen.
The first number listed on a bag of fertilizer, nitrogen, is the foundation for a healthy lawn. This nutrient is used in the greatest quantity and is quickly absorbed or leaches from the soil, requiring additional applications for best growth.
The total number of yearly applications depends on your preferred level of maintenance. Even the lowest maintained lawns will benefit from the September application. Higher maintained lawns might require an additional two to three applications over the course of the coming year.
Phosphorus, the second number listed on the bag, benefits the growth of roots and shoots. Adequate quantities are likely present in the soils of established grass. Potassium, the third number listed, is essential for the overall health, stress resistance, and cold hardiness of lawns. Like phosphorus, it is typically found naturally in our soils.
Applications of fertilizers containing additional phosphorus and potassium are not recommended unless a soil test indicates the need. Spread a starter-type fertilizer, one higher in phosphorus, when overseeding the lawn to help encourage the quick establishment of the new seed. Based on the needs of the grass and soil conditions, fertilizers containing higher concentrations of nitrogen should be applied in September.
When choosing a fertilizer, the bag will have three numbers displayed. The numbers stand for the percentage of nitrogen, phosphorus, and potassium contained in the bag. Examples of fertilizer ratios applied in the fall have numbers like 30-0-0, 27-3-3 or 25-5-5. The percentage of nitrogen should be close to 30 and the other numbers closer to 0.
Bluegrass and tall fescue grasses have the longest stretch of desirable growing conditions through the fall months. Fall growth develops new roots, crowns, rhizomes, and shoots to naturally thickening up the stand. Ultimately, fall fertilization provides nourishment when the plants need it the most.
Many may think spring fertilization of cool-season lawns is the ideal time. While spring is a time of active growth for plants, this is not the case with bluegrass and tall fescue. Applying a spring fertilizer to the grass leads to a flush of shoot growth. While this flush looks robust, it causes you to mow more frequently, weakening the grass.
Spring fertilization will exhaust the plant’s food reserves built up with fall fertilization. This results in little energy for the stressful summer ahead. It is best to wait to fertilize in the spring until May. Then a dose of nitrogen may be necessary for irrigated lawns to maintain summer color.
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 downstream, polluting the water in streams and ponds.
This summer in Kansas City has been a roller coaster of temperatures and rainfall. For success next spring, the lawns will thrive with this important fall fertilization.
Dennis Patton is a horticulture agent with Kansas State University Research and Extension. Have a question for him or other university extension experts? Email them to garden.help@jocogov.org.