The #1 lawn mowing rule experts never break

Everyone has their own lawn care routine. But if yours involves cutting the lawn short for that golf-course look, you may want to rethink your strategy. There's a lawn mowing rule that experts generally follow: Never take off more than 1/3 of the height of the grass.

“Grass blades are like solar panels, absorbing energy from the sun and sending it down to the roots," explains Frank Rossi, associate professor of horticulture at Cornell University’s School of Integrative Plant Science. "When you cut off all that foliage, the grass is forced to live off its energy reserves, and a stressed-out lawn is not going to look very good."

Rossi recommends following the 1/3 rule when you're mowing your lawn. It may leave your grass longer than you’re used to, but besides reducing plant stress and water loss, it also means you won’t have to mow as often, "about 25% to 35% less frequently," says Rossi.

Below, Rossi explains more about the 1/3 rule, how to set your mower to the correct height, and other tips to help your lawn stay healthy all summer. If you're looking for more lawn care tips, read up on why a lawn expert says you shouldn't mow wet grass and the fall lawn step you shouldn't skip.

Here’s what the 1/3 rule looks like in practice:

For best results, lawn care experts recommend letting the grass grow to a little more than 5 inches, then cutting it back to around 3.5 inches, removing about 1/3 of the blade.

Compare that with someone who cuts their lawn down to 2 inches, going for a more manicured look. To do that and still follow the 1/3 rule, they will need to cut the lawn when it reaches 3 inches. That’s 1 inch of growth between cuttings versus 1.5 to 2 inches under the best-practices scenario. Which translates into mowing every 5 days instead of every 8 or 9 days. Multiple that out over the course of the entire growing season, and you get back a few extra Saturdays!

Rossi is a big fan of robotic lawn mowers, which he estimates are now used on about a third of the lawns in Europe, though they're just starting to gain popularity in the U.S. Robotic mowers only trim a little of the lawn at a time using small, razor-like blades. More frequent mowing keeps the lawn healthy and also provides natural fertilizer in the form of nutrient-rich fine clippings.

How to set your mower height

Most of the lawn mowers tested by our experts in the Good Housekeeping Institute Home Improvement & Outdoor Lab have an adjustable deck, usually with a notched lever that raises or lowers the wheels in 1-inch or 1/2-inch increments, adjusting the distance between the deck and the ground. Always measure the height of the mower blade from the ground, ideally the driveway or other level surface to get an accurate reading. You might discover that the notches are a bit off, maybe in such a way that the 4-inch setting is best for cutting your lawn to the desired 3.5-inch height.

More lawn care mistakes to avoid

For a lush, healthy lawn, you'll want to watch out for these bad habits:

✔️ Mowing with a dull blade. It will tear at the grass blades, leaving behind jagged edges that loose water and invite disease. Experts recommend sharpening your blade every 10 hours of mowing. It’s a good idea to have a second blade that you can use while the first is at the hardware store or lawn mower repair shop.

✔️ Bagging, instead of mulching. Lawn clippings are a natural source of nutrients for the lawn that can reduce fertilizing needs by 25% or more. So instead of bagging them (which adds time and effort to the chore), use your mower’s mulching mode to deposit the clippings back onto the lawn.

✔️ Pulling every last weed. Forget about the perfect, weed-free yard. It’s tough to achieve without pumping the lawn full of chemicals. Plus, some weeds are actually good for turf grass. Clover, for examples, pulls nitrogen from the air and feeds it to the soil.

✔️ Watering every day. A daily sprinkling won’t help your lawn’s root system. A good long soak once a week (or every few days during high summer) is a better irrigation strategy. Lawns need about 1 inch of water per week, including rainfall. An empty tuna can is a good way to keep track. Most cans are 1 to 1.5 inches tall, so you can leave one outside to see how much rainfall (if any) your lawn receives each week, supplementing with a sprinkler or other form of irrigation as needed.