The first thing to understand about fertilizer is what the numbers (such as 10-10-10) on the front of the bag mean. The first number represents nitrogen (N), which promotes a deep green color, and blade growth. The second number represents phosphorus (P) which promotes root growth. The third number represents potassium (K) which promotes cell function and absorption of trace elements.
Nitrogen is the most important element for lawn grass. It produces green color, sturdy growth and dense shoots which help to crowd out weeds and resist insects and diseases. But too much nitrogen is just as harmful, because excess nitrogen can burn grass roots and fast, lush growth can attract insects and encourage fungal disease. Choose a product with a slow release source of nitrogen and follow recent recommendations to apply at a rate of ½ pound per 1000 square feet.
Applying fertilizer in the fall (the end of October through early November) is the most important time to ensure a healthy lawn. Using a fertilizer formula such as 13-25-12 will provide phosphorus that will stimulate root growth through November and even into early December. By helping roots grow before the cold weather of winter arrives, you will be rewarded with dense turf that resists winter weeds, promotes spring recovery and green-up, and creates a lawn that is more resistant to disease and drought.
With cooler temperatures, the rate which grass is growing slows down so you may not need to mow every week. But when you do, continue to mow at the recommended height for the type of grass that you have: Bermuda (1-1/2”), Zoysia (2-1/2”), Fescue (3”), St. Augustine (3-1/2”) and Buffalo (4”), and use a mower with a mulching attachment so that nitrogen in the cut grass blades stays on the lawn (and out of the landfill).
If your lawn is planted with Fescue, add another chore to your list: over-seeding. Some advocate over-seeding Fescue in the spring, but I have found that early fall is the best time because it allows for more growing time under ideal growth conditions. Cool season grass like Fescue germinates best when soil temperatures are 50-65 degrees F. which usually occurs when daytime temperatures are 65-70 degrees F. Seed germinates in 10-14 days if the soil is kept consistently moist. This is easily accomplished by setting the lawn zones to run for 5 minutes in the morning and 5 minutes in the early evening just until germination occurs (contact the Town for permission when water restrictions are in place).
I encourage you to turn off your automatic sprinkler system, but remember that when the lawn goes dormant it still needs water (just not as much). If it hasn’t rained for several weeks, turn on the sprinkler and apply ½” of water. If a hard freeze is predicted, irrigate to help reduce freeze injury to the grass; it takes much colder air temperatures to lower the temperature of a moist soil than that of a dry soil.
The next time to fertilize will be in mid- to late-spring when the grass is actively growing. Resist the temptation to fertilize too early as this can lead to abundant, but thin, grass blades that are susceptible to damage and disease.
If you develop spring fever before this time, consider top dressing the lawn with compost. Top dressing adds organic matter to soil, builds up soil flora, revitalizes microorganisms in the soil, helps with water retention, relieves compaction and reduces thatch.
In the meantime, enjoy the time off from lawn chores, knowing that you’ve given your lawn a head start for the spring.