How you water is one of the most important factors affecting your lawn’s health. It might be tempting to error on the side of overwatering, but that only leaves your lawn vulnerable to disease, fungus, and soil compaction, and leads to a weak root system.
There are no hard-and-fast rules to lawn watering, but understanding your grass type, soil type, and climate will help you find the schedule that works best for your lawn.
How Often Do You Really Need to Water?
A new lawn, whether seeded or sodded, needs attentive watering to give it the best chance of survival. Aim to keep the top 1 inch of soil consistently moist but not soggy, which usually requires misting twice a day. Once the seeds germinate, keep the top 2 inches of soil moist until the new grass reaches a height of at least 3 inches. After that, water as needed.
Once established and healthy, a lawn doesn’t necessarily need anything more than rainfall. Turfgrass is tough. Many species can survive up to four weeks without water by going dormant. They’ll turn brown, but green up again when the rain returns. Species popular in hot, dry climates are particularly well adapted to periods of drought. After a month with no rain, though, even these grasses need irrigation to survive.
That said, most lawn grasses grow best when the top 6 to 8 inches of soil is moist. On average, to maintain that moisture level, a lawn needs at least 1 to 1.5 inches of water a week, either from rain or irrigation. One to three watering sessions a week is ideal. Avoid frequent, shallow watering, which discourages the lawn from building the deep root system it needs to survive hot weather.
In climates where air temperatures don’t fall below freezing, lawns need the same amount of water in winter. Too little water during the cold season stresses the grass and increases the risk of damage.
This amount is just a guideline, though. Your grass species, condition, soil, and weather conditions also affect your lawn’s watering needs. Cool-season grasses, particularly fescues, need extra watering during hot periods. Taller grass holds moisture better than shorter grass. Heavy thatch buildup is hard for water to penetrate, but it holds in moisture, so the lawn will need more water than average, but less frequent watering.
Clay soils are similar. They’re slow to absorb water, but they hold water longer than sandy soils. Grass in clay soil benefits from getting its weekly water in one go. Grass in a fast-draining sandy soil benefits from more frequent watering. Grass in a sunny area or on a slope needs more water than grass in the shade or on flat ground. While it’s obvious heat dries out your lawn, don’t overlook the drying effect of wind.
Most grasses give you a sign when they need water, such as wilting or turning from green to a dull, blueish-gray. If you can walk across the grass and leave clearly visible footprints, it’s time to water. If you’re unsure, try pushing a 6-inch screwdriver into the soil. If you can’t push it all the way in with little resistance, chances are your lawn needs water.
Also, beware of overwatering. Don’t assume brown spots mean a lack of water. Fungus, insects, soil issues, and even overwatering can all leave brown patches. If you have heavy clay soil, compacted soil, or you haven’t watered in a long time, you might see water run-off before you’ve watered much at all. Aeration can solve the compaction problem, and adding soil amendments such as aged compost can lighten clay soil.
If you know your soil isn’t the issue, you might need to water more often. In the meantime, when you notice run-off, turn the sprinkler off and let the water soak in for 10 minutes, then continue watering. You might need to water in a cycle of 10 minutes on and 10 minutes off.
Setting Your Watering Schedule
Once you know how much water your lawn needs, you can choose a schedule that meets those needs. Rain gauges are the most accurate way to measure how much water you’re giving your lawn, but since most tuna cans are 1 inch high, they also make handy measuring devices.
Because sprinklers don’t always reach every part of the lawn equally, measure coverage in several areas. Place rain gauges or empty tuna cans in different parts of the lawn and time how long it takes the sprinkler to fill them with 1 inch of water. For most sprinklers, it’s around an hour.
Alternatively, let the sprinkler run for 30 minutes and check how much water it puts out. If it’s half an inch, you’ll know you need to water for an hour to give your lawn a full inch. If you’d rather not monitor your sprinkler, buy a sprinkler timer that measures water flow. Multiply your lawn’s square footage by 0.62 gallons (the amount that gives you an inch of water for each square foot) to find out how many gallons to set the sprinkler for.
If your sprinkler puts out an inch of water every 30 minutes, you can break your watering into one 30-minute session, two 15-minute sessions, or three 20-minute sessions depending on your lawn’s individual needs at the time. You’ll still need to adjust for weather conditions, watering more during hot, windy periods and cutting back during wet periods.
When possible, water before 10 a.m. when it’s cooler and less windy, which reduces evaporation and stress on the grass. If the evening is the only time you can water, try to get it done between 4 and 6 p.m. when the heat of the day has passed, but the grass still has time to dry before sundown. Grass that stays wet overnight is more vulnerable to disease and fungus. Avoid watering during the hottest part of the day, usually between 10 a.m. and 2 p.m.
Watering 1 to 1 1/2 inches a week is a good guideline to start with, but to keep your lawn in optimal health, refine your watering plan to meet your lawn’s individual needs. The grass species, condition, location, soil type, and the current weather all affect your lawn’s water requirements. When in doubt, pay attention to wilting, color changes, and other signs to determine how often and how much to water your lawn.