First, know which grass you have
Lawn grasses fall into two groups, and they grow at opposite times of year.
- Cool-season grasses such as tall fescue, Kentucky bluegrass, perennial ryegrass and fine fescues grow most in spring and fall and slow down in summer heat. They dominate lawns in the northern half of the US and the transition zone.
- Warm-season grasses such as bermudagrass, zoysiagrass, St. Augustinegrass and centipedegrass grow most in summer and go dormant (brown) after frost. They dominate the South.
The rule is simple: feed the grass while it is growing, not while it is resting.
Cool-season lawns: focus on fall
For fescue, bluegrass and ryegrass, early fall is the most valuable feeding of the year. The grass is recovering from summer stress and storing energy for winter and next spring.
- Main feeding: late summer to early fall. University of Illinois Extension advises that if you only fertilize once a year, do it in late summer or early fall, roughly mid-August to mid-September in central Illinois (earlier in the north, later in the south).
- Second feeding: late spring. UConn’s soil lab suggests timing applications around May and early September.
- How much per year: UConn suggests about 2 pounds of nitrogen per 1,000 square feet a year if you leave clippings on the lawn, or about 3 pounds if you bag them, because clippings return nitrogen to the soil.
Avoid heavy feeding in midsummer. Cool-season grass is stressed by heat then, and lush growth is more prone to disease.
Warm-season lawns: feed through summer
For bermudagrass, zoysia, St. Augustine and centipede, fertilize from late spring, once the lawn has fully greened up, through summer while it is growing strongly.
- Start after green-up, not at the first warm day. Feeding a lawn that is still half dormant mostly feeds early weeds.
- How much per year depends on the grass. Virginia Cooperative Extension notes that centipedegrass and mature zoysiagrass do best on about 1 to 2 pounds of nitrogen per 1,000 square feet a year, while bermudagrass and St. Augustinegrass can use more, up to about 3 pounds or more in high-maintenance programs.
- Stop in late summer. Fertilizing warm-season grass in fall or winter, when it is slowing down or dormant, wastes fertilizer and can make the grass more vulnerable to cold damage.
How much to apply each time
Lawn fertilizer rates are given in pounds of nitrogen per 1,000 square feet, not pounds of product. Extension guides commonly cap quick-release nitrogen at about 1 pound per 1,000 square feet per application; Virginia Tech recommends no more than 0.9 pound of mostly water-soluble nitrogen at once. Slow-release products can be applied at somewhat higher rates according to the label.
To turn that into pounds of product, divide the nitrogen rate by the first number on the bag (as a decimal). One pound of nitrogen from a 24-0-6 fertilizer is 1 ÷ 0.24 ≈ 4.2 pounds of product per 1,000 square feet. Our lawn fertilizer calculator does this for any bag and lawn size, and builds a yearly plan for your grass type.
Sample schedules
| Grass | When to feed | Typical yearly nitrogen |
|---|---|---|
| Cool-season, clippings left | Late spring + early fall | About 2 lb per 1,000 sq ft |
| Cool-season, clippings bagged | Late spring + early fall, plus early summer if needed | About 3 lb |
| Bermuda, St. Augustine | Late spring through late summer, every 6–8 weeks | About 2–3+ lb |
| Zoysia, centipede | Late spring and midsummer | About 1–2 lb |
These are general starting points. Your state’s cooperative extension service publishes schedules tuned to your climate.
Common fertilizing mistakes
- Skipping the soil test. A test tells you whether you need phosphorus or potassium at all, and whether low pH is the real problem. If your soil is too acidic, fertilizer won’t fix a thin lawn; lime will. See our guide to reading a soil test and the lawn lime calculator.
- Feeding a dormant or drought-stressed lawn. Grass that isn’t growing can’t use the nitrogen.
- Applying before heavy rain. Rain can wash granules into storm drains. A light watering afterward is fine if the label calls for it.
- Leaving granules on pavement. Sweep them back onto the lawn.
- Uneven spreading. Apply half the product in one direction and half at right angles to avoid stripes.
Sources
- University of Illinois Extension: Five fall tips for cool-season lawn care
- UConn Soil Nutrient Analysis Laboratory: Lawns
- Virginia Cooperative Extension: Soil test note for lawns