When to Fertilize Your Lawn

With fertilizer, when matters more than how much. Feed at the right time and the grass uses it to grow roots and thicken; feed at the wrong time and you either waste it, burn the lawn, or hand the food to weeds. The whole schedule hinges on one thing: what kind of grass you have.

First, know your grass season

Cool-season grasses (fescue, Kentucky bluegrass, ryegrass) grow hardest in spring and fall. Warm-season grasses (Bermuda, zoysia, St. Augustine) grow hardest in late spring and summer. You fertilize when the grass is actively growing, so the timing flips depending on which you have. Not sure? The grass type selector sorts it out.

Cool-season timing: fall is king

For cool-season lawns, fall is the most important feeding of the year — the grass pours it into roots ahead of winter and comes back thick in spring. A lighter spring feeding helps it green up, but skip heavy spring nitrogen: it pushes soft top growth right as summer stress arrives. Rough rhythm: light early spring, then the big one in early-to-mid fall.

Warm-season timing: late spring into summer

Warm-season lawns wake up later, so their feeding window is late spring through summer, once the grass is fully green and growing. Feeding too early — while it's still dormant and brown — just feeds weeds. Space feedings through the growing season and taper off before fall, since late feeding leaves warm-season grass vulnerable heading into cold.

How much, and building a schedule

Once the timing is right, size the amount to your lawn with the lawn fertilizer calculator, which turns your square footage and the bag's numbers into how much to spread. To lay the feedings out across the year for your grass, the fertilizer schedule and the broader lawn care schedule put every task on a calendar.

When NOT to fertilize

Skip it on dormant grass (brown and not growing), during a drought or heat wave (you'll stress or burn it), and right before heavy rain (it washes off into storm drains — wasted money and bad for waterways). And don't fix a thin lawn with fertilizer alone: if the soil's off, feeding does little. A quick soil test tells you whether you even need it. The bigger picture is in Lawn Care 101.