How to Fertilize a Lawn Without Burning It

Warm-season and cool-season grasses grow in different parts of the year. Warm-season grasses such as bermudagrass, zoysiagrass, St. Augustinegrass, centipedegrass and bahiagrass grow best in summer, go dormant at the first heavy frost and turn brown, then green up slowly the next spring. Cool-season grasses such as tall fescue, Kentucky bluegrass, fine fescue and perennial ryegrass grow best in spring and fall, grow less in summer and stay reasonably green through winter.

Outside its growing season the grass is less likely to absorb the nutrients, which can then leach into nearby water. A bahia lawn that stays thin after feeding may have another problem, which bahia grass thinning covers.

Extension calendars differ by region, and each row below is that state's own advice.

For cool-season grass, fall is the common window in the rows above. Colorado State calls it the best time to feed bluegrass, because the lawn goes into winter with a healthier root system and greens up earlier in spring without the excess top growth, or the mowing chores, that spring feeding brings.

Spring and summer feedings carry a risk, since high rates, or repeated low rates, of nitrogen on cool-season grass greatly increase the severity of brown patch, a disease that can kill the grass. The fall fertilizing guide covers that season in more detail.

A warm-season lawn gets its first nitrogen of the year once the grass has greened up and is growing, and skipping fall and winter nitrogen reduces winter injury. Texas lawns follow their own calendar in the Texas lawn fertilizer timing guide.

Maryland law restricts when lawn fertilizer can be applied, and many Florida cities, counties and communities have fertilizer ordinances that vary by location, so check your local rules before you pick a date.

The three numbers on a bag give the percent of nitrogen, phosphorus (as phosphate) and potassium (as potash) by weight, and the first number is nitrogen. Nitrogen is the nutrient a home lawn needs on a regular basis, and it is also the one that often burns the lawn at an excessive rate. Phosphorus is a different case, because established lawns respond little to it and a soil test should show the need before you add any.

Extension guidance from Minnesota, South Carolina and Florida keeps a single feeding at 1 pound of nitrogen per 1,000 square feet or less, and Clemson uses half a pound for low-maintenance lawns. To turn pounds of nitrogen into pounds of product, divide 100 by the first number on the bag. A 16-4-8 bag needs 6.25 pounds per 1,000 square feet to deliver 1 pound of nitrogen, and 3.13 pounds to deliver half a pound.

Release speed changes how easily a product burns the lawn.

A soil test every two to three years shows how much lime, phosphorus and potassium an established lawn needs, and skipping the test can lead to under- or overfertilization. Leaving the clippings on the lawn may reduce the need for fertilizer by 20 to 30 percent.

Every rate above is per 1,000 square feet, so the lawn's area comes first. Measure it yourself or read it from a property survey. Split the yard into rectangles and triangles, multiply length by width for each, and add them. For a 5,000 square foot lawn fed with the 16-4-8 bag, 6.25 pounds per thousand comes to about 31 pounds of product.

The label setting is a good starting point but is not always accurate, because the output changes with the size, weight and density of the product and with how fast you walk. A faster pace lowers the rate and a slower pace raises it, so the test below is worth repeating for each fertilizer and for each person who will push the spreader.

Plan two coverage passes at right angles to each other, each at half the rate, so every part of the lawn is covered twice. Clemson's example for a 1 pound rate puts 0.5 pound on each pass. A drop spreader suits smaller areas and the edges of the lawn, because it spreads only as wide as the hopper.

Burn is most common when a lawn is fertilized in hot weather or without being watered, and practically all inorganic fertilizers can burn grass foliage if they stay on it. Watering rinses the granules off the blades and into the soil, so water in unless the label says otherwise.

Watering needs only enough to rinse the blades and wet the top 1/2 inch of soil.

Storms or flooding wash fertilizer away before the lawn can use it, and fertilizer left on a sidewalk, driveway or gutter adds substantially to nutrient runoff into lakes and streams. Sweep up spills instead of rinsing them away.

A new lawn is fed on a different schedule. NC State applies a starter fertilizer high in phosphorus when the site is prepared and fertilizes seedlings about six to eight weeks after they emerge, and UF/IFAS says to wait at least 30 to 60 days after planting so the roots can establish first.

Fertilizer burn usually looks like drought stress, because excess fertilizer salts keep roots from absorbing or retaining enough water. Since the symptoms resemble drought, check whether you overlapped spreader passes, used a wrong spreader setting, or spilled fertilizer from the spreader or an open bag.

Collect any spilled fertilizer first. Then dilute what is left by soaking the area with 1 inch of water, enough to fill a rain gauge to 1 inch, and repeat that two or three times to leach the excess salts out of the soil. Grass that dies from too much root loss has to be replanted, and the steps for that are in the overseeding guide.

A weed-and-feed bag combines fertilizer with a herbicide, and University of Minnesota Extension lists several reasons it may not be the best choice. The best time to kill a given weed is often not the best time to feed the lawn, and crabgrass preventers belong on much earlier in spring than fertilizer does.

The watering rule is where the two jobs collide. Watering in protects the lawn from burn, but many herbicides need to stay on the plant leaves to work, so the label has to say whether to water in. Where only a few weeds grow, spot treating them is just as easy as covering the whole lawn, and applying fertilizer and weed killer separately is the best approach for the environment.