Updated: Oct 6, 2020
It’s not unusual to fertilize your lawn in the spring, but don't let the cooler temperatures of autumn fool you. Fall actually is the best time to fertilize the grass, even better than springtime. After the summer's heat and humidity, grass regains its strength before winter with a good fall fertilizing. Fertilizing now also helps grass develop a thick and deep root system, so it can better survive next summer's heat.
A soil test is the best way to determine what nutrients are lacking in your lawn. Test for nitrogen, phosphorous and potassium, as well as the soil's pH level.
Assess if your yard is planted with cool season or warm season grasses. It's the cool season grasses - bent grass, Kentucky bluegrass, fescue and ryegrass varieties – that benefit from fall fertilizing. Cool season grasses are generally planted in locations with cold winters and warm to hot summers.
CHOOSING A FERTILIZER
Nitrogen, phosphorous and potassium are the three primary components in lawn fertilizer. The shorthand is N-P-K.
Nitrogen builds strong grass and roots. It keeps grass green and protects it from diseases.
Fall fertilizers include phosphorus for stronger roots. A lawn with adequate phosphorus can better fight diseases and is more tolerant to heat, cold and drought.
Potassium helps to protect the grass and roots from winter's extremely cold temperatures.
Gypsum also could be present in the fertilizer. It loosens heavy clay soils and improves absorption of nutrients. Loose soil makes it easier for new spring grass to break through.
Your soil's pH level will indicate its chemistry. If the pH level shows a need to reduce acidity, apply lime. If alkalinity needs to be reduced, apply sulfur.
The bag's label shows the N-P-K concentration by weight using a series of three numbers. For example, a 50-pound bag of fertilizer that's labeled 5-10-5 is comprised of 2.5 pounds (five percent) nitrogen, five pounds (10 percent) phosphorus and 2.5 pounds (five percent) potassium.
Larger numbers indicate greater concentration of the nutrients. The concentration determines the lawn area that a bag of fertilizer will cover, so follow the manufacturer's application directions.
Some fertilizers release their nutrients quickly, while others release it slowly. Determine which is best for your fall application given your grass and climate. Slow-release fertilizers result in longer, more even feeding, while fast-release products deliver nutrients to the grass quickly in advance of cooling soil and air temperatures.
If your lawn has a lot of shade, it may not require as much fertilizer. Shady lawns generally grow more slowly than sunny lawns. Check the label for any special directions for shady conditions.
While the top growth of your grass slows or stops altogether in cooler autumn temperatures, the roots continue to grow.
Three fall fertilizer applications properly prepare your yard for winter. Apply the initial treatment in early September. Apply the second feeding in late October and a third feeding in December (S-O-D). The N-P-K nutrients feed the roots to keep the grass strong during the winter. They also provide reserves for a green and quick growth spurt in the spring.
Fertilizer dissolves more easily and quickly into soil that's somewhat moist. If your yard is very dry, give it a good watering and then wait a day to fertilize. Otherwise the fertilizer's ingredients won't be as effective.
What are your autumn lawn fertilization tips? Tell us in the comments area below.