Try to give your lawn the water it needs—and no more. This moderate approach conserves an important resource, saves money, and helps prevent grass diseases caused by too much water. How much water your lawn needs depends on the health of your lawn and soil, the amount of rainfall your lawn gets, and the climate. You may need as few as two waterings a year or as many as two a week.
The best approach to watering grass (and most other plants) is to follow nature’s pattern of rainy periods followed by brief dry spells. Apply enough water all at once to penetrate to roots, let the soil almost dry out, and apply water again. Grass signals that it needs water by losing its spring: When you walk across the lawn and see your footprints, your lawn probably needs to be watered.
To determine how much water your lawn needs, you need to consider several factors: the depth of your grass roots, your soil type and its “penetrability,” your irrigation method, and of course the weather. First, check to see how deep the roots of your grass grow. Add an inch to the average root depth to arrive at a target watering depth. It makes no sense to waste water by watering to a level substantially deeper than you lawn’s root zone.
Root depth depends on how much time you have taken to improve your soil and on the type of grass you are growing. Some grasses, such as tall fescues, have roots that reach 1 foot deep. Others grow to only half that, in even the best conditions. As your grass develops deeper roots, adjust your watering-depth target so that you continue to encourage roots to go deeper.
Next, determine how much water is needed to moisten soil to the root zone. A good rule of thumb for most grasses is 1 to 2 inches per week. If you have porous soil that drains quickly, you would apply 1 inch of water twice a week. Conversely, if your soil holds water well, a good guess would be 1 1/2 to 2 inches once a week.
To determine how long you should run your sprinkler to deliver the desired amount of water, wait for a four- to five-day dry spell. Set out some empty cans in various locations on the lawn. Run your sprinkler or in-ground sprinkler system until the cans contain 1 inch of water. Wait 24 hours to allow the water to penetrate the soil (12 hours if your soil is porous since porous soil drains faster), and then check the depth of the moisture penetration.
If 1 inch of water moistens soil to a depth well beyond the root depth, try the procedure again after your soil has dried, but turn off the sprinkler sooner. Conversely, if the root depth is not reached, try delivering more water. Keep accurate records of how long you need to run your sprinkler or sprinkler system to deliver the required amounts of water for your lawn, and then base future waterings on what you’ve learned from your observations.
If it rains during the week, decrease your watering by the amount of rain that fell. If it’s hot and sunny or windy, you may need to increase the watering amount and frequency.
If you find that your lawn dries out quickly and needs more frequent watering than other lawns in your neighborhood, there are ways to minimize waterings.
1. Keeping your grass relatively tall will help the plants reduce moisture evaporation by shading the soil.
2. If you choose native grasses or those well adapted to your area when seeding, they will need less watering. For example, Blue grass is a guzzler; Buffalograss is not.
3. Improving your soil can also help reduce your watering needs. Try top dressing your soil with organic material. Then work it into the soil using an aerator (with a core cultivator). Organic material helps your soil hold water longer.
4. In addition, aeration promotes deeper root growth. When combined with infrequent, deep waterings, aeration enables grass plants to take moisture from a greater soil area.
5. Don’t use chemicals. Organic lawns require less watering than chemically treated lawns.
6. Use a sharp mower blade to make cleaner cuts. Cleanly cut lawns look greener and cause less evaporation than raggedly cut lawns.
7. Do not overfertilize.
8. Allow your lawn to temporarily brown out, or go dormant, when drought conditions persist. Usually this will not hurt a healthy, established lawn because the roots continue to live and are ready to send forth new shoots when conditions improve. There may be times during the year when it’s just not worth trying to keep your lawn green (but continue to water lawns less than a year old through dry spells.)
9. If you have an automatic sprinkler system, check for consistency of coverage. Uneven coverage often causes homeowners to overwater some areas in order to adequately water others.
10. If you water your lawn manually, invest in a timer (either built into the sprinkler or installed at the outdoor faucet). With a timer, you can’t forget to turn off the sprinkler. The flip side to using programmable timers, however, is that they turn on the system rain or shine. There’s nothing more wasteful than sprinklers watering during a heavy rainstorm. In-ground systems with soil or weather sensors avoid that problem.