If you’re an average homeowner (and of course you’re not!), you spend 3.8 hours a week on yard work and mow your lawn 30 times a year. And while you may not realize it, your lawn pays you back for all this hard work. It serves as a giant air conditioner to help cool your home. It releases a tremendous amount of oxygen and captures tons of dirt and dust to help keep you and your family healthy. It gives you a place to play croquet. And the healthier your lawn is, the better it keeps up its end of the bargain.
The good news is, you don’t have to slave over your lawn to keep it healthy. In fact, to a great extent, it’s not the amount of work you put into your lawn—it’s when and how you do it. The following five “ingredients” are essential for a healthy lawn. We focus on northern or cool-climate grasses like bluegrass and fescue, but most of the information applies to warm-climate grasses like zoysia and Bermuda grass, too.
For cool-climate grasses, use a 1-1/2 in. cutting height for the first mowing of the year to remove dead grass and allow more sunlight to reach the crowns of the grass plants. Raise the blade during the heat of summer to 2 or more inches. Then lower the blade back to 1-1/2 in. for the last cutting of the year. For warm-climate grasses, these heights will be about 1/2 in. lower.
When adjusting your blade height, measure from a hard surface to the bottom of the mower deck, then add 1/4 in. (most blades sit 1/4 in. above the bottom of the deck).
Cut your grass using a sharp blade (illustration below). A dull one tears grass rather than cutting it cleanly. Damaged grass turns yellow, requires more water and nutrients to recover, and is more susceptible to disease. Sharpening and balancing a blade three times a year is usually enough to maintain a good cutting edge— unless you hit lots of rocks.
Use a Sharp Mower Blade
A well-maintained (sharp and balanced) blade cuts grass cleanly and evenly.
A poorly maintained (dull) blade shreds grass, leaving it more susceptible to disease and in need of more nutrients to repair the damage. An unbalanced blade compounds the problem (and can damage your lawn mower’s bearings).
Deep watering helps develop deep roots that tap into subsurface water supplies (illustration below). Light sprinklings wet only the grass and surface of the soil; this encourages shallow root growth and increases the need for more frequent watering. As a general rule, lawns require 1 to 2 in. of water per week (from you or Mother Nature), applied at three- or four-day intervals. But this varies drastically depending on the temperature, type of grass and soil conditions. Lawns in sandy soils may need twice as much water, since they drain quickly. Lawns in slow-draining clay soils may need only half as much.
When your lawn loses its bounce or resiliency, or when it wilts, exposing the dull green bottoms of the blades, it needs water. As a general game plan, water until the soil is moist 4 to 5 in. down, then wait to water again until the top 1 or 2 in. of soil dries out. To find out how much water your sprinkler delivers, set out a cake pan, turn on your sprinkler, then time how long it takes for the water to reach a depth of 1 in.
The best time of day to water is early morning. Water pressure is high, less water is lost to evaporation and your lawn has plenty of time to dry out before nightfall. Lawns that remain wet overnight are more susceptible to disease caused by moisture-loving mold and other fungi.
Good Watering Pays Off
Properly watered lawns receive an initial soaking 4 to 5 in. deep, and are then watered when the top 1 to 2 in. of soil dries out, develop deep, healthy grass roots. This usually means applying 1 to 2 in. of water per week at three- or four-day intervals. An impact sprinkler delivers water quickly, with less “hang time” for evaporation; a 3/4-in. hose delivers much more water volume than its 1/2-in. cousin.
Improperly watered lawns receive short daily waterings that promote shallow root growth. Oscillating sprinklers toss water in a high arc, so more evaporates before reaching the soil. Watering late in the evening when your lawn doesn’t have time to dry out allows disease-carrying fungi and mold to grow.
The top one-third of a blade of grass is thin and “leafy,” decomposes quickly when cut and can contribute up to one-third of the nitrogen your lawn needs (illustration below). While it’s decomposing, this light layer of clippings also helps slow water evaporation and keeps weeds from germinating.
But the bottom two-thirds of a blade of grass is tough, “stemmy” and slow to decompose. It contributes to thatch, which—when thick enough—prevents sunlight, air, water and nutrients from reaching the soil. Cutting more than the top third also shocks grass roots and exposes stems, which tend to burn in direct sunlight.
This means if 2 in. is your target grass length, cut it when it reaches 3 in. Since grass grows at different rates at different times of the year, “every Saturday” isn’t necessarily the best time to mow. Sometimes you need to mow it more; other times, less. The ideal length for cool-climate grasses is 3 to 4 in.; for warm-climate, 1 to 2 in.
Mow when the grass is dry and avoid mowing in the heat of the day when you’re more likely to stress the grass—and yourself.
Set the Correct Mowing Height
For the correct mowing height, cut off no more than one-third of the grass’s height at a time. The upper leafy grass clippings easily decompose, adding nitrogen to your soil.
Don’t cut off more than one-third of the overall height of the grass or you’ll not only shock the plant but also leave thick, stemmy clippings that are slow to decompose, and therefore contribute to thatch.
When applying weed killers and fertilizers, you must take into account such variables as geographic location, grass type, weed type and soil conditions. But here are a few general guidelines:
- The best defense against weeds is a thick, healthy lawn (illustration below) that doesn’t provide weed seeds adequate sunlight or open space to germinate.
- Attack weeds in the early spring and summer before they have a chance to develop deep root systems, go to seed or reproduce.
- Different weeds need to be dealt with using different chemicals and methods. It’s best to eradicate grassy weeds like crabgrass with pre-emergent weed killers, which destroy germinating plants just as they sprout. Broadleaf weeds need to be attacked while they’re young and actively growing; spraying the leaves of individual plants or patches of plants is most effective. Dandelion killers work by literally growing the plant to death.
- Fertilize in early spring to jump-start root development. Fall feedings help repair summer damage and spur the root growth that goes on for several weeks even after the top growth stops; this helps grass survive the winter. Light feedings in between help maintain healthy growth.
- Read the package. Some chemicals work only in the presence of moisture; other chemicals are rendered useless by water. Heed the safety warnings too.
The best resource for identifying and troubleshooting weeds is a nursery or garden center familiar with local conditions.
Get After Weeds Early—A Thick Lawn Will Crowd Out Most Weeds Later
A healthy lawn that’s full and hard to penetrate is your best defense against weeds. Preemergent herbicides knockout crabgrass and other grassy weeds before they have a chance to get established. Broadleaf weeds should be eradicated while plants are young by spraying herbicides directly on the leaves.
A sick, spotty lawn leaves lots of open space for weeds to take root and grow.
Grass roots need oxygen as well as water and nutrients. Aerating—the process of removing small plugs of soil (see illustration)—produces multiple benefits. It improves air-to-soil interaction. It allows water and fertilizer to penetrate the soil deeper and easier. It reduces soil compaction and opens space for roots to grow. It removes some thatch and stimulates the breakdown of the remaining thatch. The best tool for this task is a gas-powered aerator, available at most rental centers.
Again, timing is critical. You can aerate in the spring. But fall—after the kids are through trampling the grass and there are fewer weed seeds to set up home in the open spaces—is the best time to aerate. It’s usually best to aerate first, then apply any weed killers so the open holes are protected against weeds.
A Well-Aerated Lawn
A well-aerated lawn provides space for grass roots to grow, reproduce and take in more oxygen, moisture and nutrients. The plugs, composed of thatch and soil, quickly break apart and decompose.