How to Tell if Your Lawn Needs Water (7 Signs)

The lawn water deficit calculator turns what you see into inches to put back, but first you have to read the lawn correctly. Brown grass is a late sign, and wilting on soggy ground means the opposite of what it seems.

Below, the seven signs run from earliest to latest, followed by three field tests, the cases where the signs mislead, and a worked example that ends in minutes on your controller.

How to tell if your lawn needs water: the 7 signs

Lawns show water stress in a fairly fixed order. The first three signs appear while the grass is still green.

1. Footprints stay in the grass

Walk across the lawn and look back at your track. Blades with plenty of water are rigid and spring upright quickly. Blades short of water lose that internal pressure, called turgor, and stay trampled, so tracks or wheel marks that last several hours are an early sign of stress.¹ UF/IFAS extension reads the same pattern, footprints or tire tracks that remain long after they were made, as drought stress.²

2. The color shifts to blue-gray

Before it browns, stressed turf changes from green to a dull bluish-gray.² University of Missouri extension describes the tint as bluish-purple.¹

3. Blades fold or roll lengthwise

Dry grass curls its blades up lengthwise to reduce leaf area.² Look at the older leaves, because young leaves are not fully developed and can look wilted when the plant is fine.²

4. The soil is dry down to root depth

Missouri extension treats adequate moisture at 6 to 8 inches (15 to 20 cm) as enough to carry summer grass,¹ so that is the depth to check. If you are unsure how deep your roots reach, the root zone depth calculator helps you pick a depth to test.

5. The same spots wilt first

Some areas always show stress ahead of the rest: hard soils that take up water slowly, slopes, south-facing exposures and warm strips beside driveways and walks.¹ Treat them as gauges, because they give the earliest warning.

6. Blades turn straw-brown

With continued heat and no water, grass wilts first and then browns completely as it goes dormant.¹ The crown, the lower part of the plant, usually stays alive but stops growing.¹ That is why brown is a late sign rather than proof the lawn is dead.

7. Turf thins, weeds move in and the ground cracks

A prolonged shortage thins the turf and can raise weed pressure.² Extended dry periods can also open large cracks in the soil and cause heavy loss of turf cover, even after watering resumes.¹

The seven signs by stage, with the check that confirms each

Three quick tests that confirm the signs

Run each test in two places, one hot spot and one ordinary spot, to see whether to water everything or only the problem areas.

• Screwdriver test. Push a slender, foot-long screwdriver into the lawn in several places. It slides in easily where the soil has had enough water.¹ Compare a hard spot with a patch you watered yesterday, because compacted soil can resist even when it is moist.
• Squeeze test. Press a golf-ball-sized handful of root-zone soil together. Soil that holds together without crumbling and looks moist has been watered properly. Soil that is dry and dusty and will not form a ball has had too little water, or the water ran off instead of soaking in.¹
• Shovel wedge test. The day after a watering, cut a slender wedge of turf about 2 inches (5 cm) wide and 6 to 8 inches (15 to 20 cm) deep. The soil, roots and turf go back in without harm.¹ For a number instead of a feel, use the soil moisture calculator.

How much of the lawn has to show signs before you water?

Extension sources give two rules, and the right one depends on how green you want the lawn to stay. University of Missouri extension says to water within a day of seeing the symptoms.¹ UF/IFAS says to consider watering when you see at least one of the three classic signs, and to irrigate when 30 to 50 percent of the lawn shows wilt if you want it uniformly green through a dry spell, unless rain is forecast within 24 hours.²

Grass type changes the slack you have. Warm-season grasses can survive extended drought by going dormant, if you accept some wilt and browning.² Cool-season turf needs more: UC data put survival-level watering for tall fescue at about 60 percent of ETo, against about 40 percent for bermudagrass.⁴

When wilting does not mean the lawn needs water

Grass can wilt in wet soil. Missouri extension calls this wet wilt: the soil is obviously wet, but the roots cannot keep up with what the atmosphere demands, and the curling looks almost identical to drought wilt.¹ Lawns with shallow roots after a rainy spring are the most exposed, and adding water starves the roots of oxygen.¹

Overwatering is the most common lawn mistake, and UF/IFAS lists shallow roots, more weeds, insects and disease, and more thatch among the costs.²

If the lawn looks stressed on wet soil, ask your county extension office or a local turf professional to look at it before you add water.

How much water to give once the signs show

Two extension figures cover most lawns. UF/IFAS puts the right amount at 0.5 to 0.75 inch (13 to 19 mm) per watering for most Florida soils, and notes that sandy soil wets down about 12 inches (30 cm) for each inch applied while heavier soil may need only half an inch.² Missouri extension works by the week: once you decide to irrigate, supply a week of water, spread over two or three days if the soil takes it in slowly, then wait for the signs before irrigating again.¹

Weekly water once irrigation starts, by grass and lawn condition

Missouri extension figures, where turf ET in central Missouri in July and August is about 4 inches (100 mm) a month. Hotter, drier climates need more. Dormant means the lawn may turn brown but will not die.¹ For other grasses, see the lawn watering by grass type chart or the grass type water needs calculator.

Water only as fast as the soil can take it in. Most Missouri soils absorb about 0.25 to 0.5 inch (6 to 13 mm) an hour,¹ so a sprinkler that applies more than that causes runoff. UC suggests watching one cycle from the start until runoff begins to find the longest run your soil allows.³ The soil infiltration rate calculator helps you estimate your own soil's intake.

1. Estimate what the lawn used. Multiply daily ETo by Kc, then by the days since the last watering or soaking rain. Get daily ETo from a local weather network or the evapotranspiration calculator.
2. Correct for uneven coverage. Divide by DU. Use 0.7 as a planning figure if you have not tested, or measure it: set straight-sided cans, such as tuna cans, across the zone, run the system and compare depths, which should all be about equal.² The catch-can test calculator handles the arithmetic.
3. Convert depth to minutes. Divide the depth by your precipitation rate and multiply by 60. If you do not know the rate, the sprinkler precipitation rate calculator finds it, and the how long to water lawn calculator returns minutes per zone.
4. Split long runs. If runoff starts before the run ends, stop and resume after the water has soaked in. The cycle and soak calculator sets the cycle length.

Worked example: tall fescue on loam, signs on day 3

Take a 5,000 sq ft (465 m²) tall fescue lawn. Three days after the last watering, with no rain, footprints stay in the grass and a blue-gray cast shows across the sunny side. ETo has averaged 0.2 inch a day (5 mm), the rotors apply 0.5 inch an hour (13 mm/h), and DU is an assumed 0.7.

1. Daily lawn use0.2 × 0.8 = 0.16 in
2. Used in 3 days0.16 × 3 = 0.48 in
3. Water to apply0.48 ÷ 0.7 = 0.686 in
4. Run time0.686 ÷ 0.5 × 60 = 82 min
5. Cycles2 × 41 min, 0.34 in each
6. Volume5,000 × 0.686 × 0.623 ≈ 2,137 gal

About 82 minutes, split into two 41-minute cycles

Metric: 0.16 in is 4 mm a day, 0.48 in is 12 mm used, and 0.686 in is 17 mm applied at 13 mm/h for 82 minutes, about 8,100 liters over 465 m².

Check the result against the extension ranges. The 0.686 inch applied falls inside the 0.5 to 0.75 inch per watering that UF/IFAS gives,² and each 41-minute cycle puts down 0.34 inch, inside the 0.25 to 0.5 inch that Missouri soils take before runoff.¹

What if the lawn is already brown?

Brown blades usually mean dormancy before they mean death. The crown normally stays alive, and a thorough watering or soaking rain brings the lawn out of dormancy as new leaf tissue resumes.¹ Recovery is not guaranteed after a long dry spell, because extended dryness can still cause cracking and loss of turf cover.¹

Keeping a lawn alive takes far less water than keeping it green. Missouri extension lists 0.5 inch (13 mm) a week for dormant tall fescue against 0.8 inch (20 mm) for green fescue, and 0.2 inch (5 mm) against 0.5 inch (13 mm) for zoysia or bermuda in the weekly water table above.¹

To test a brown patch, water a small area thoroughly and watch the base of the plants for new leaf tissue. A patch that stays brown while the lawn around it recovers may have dead crowns or another problem, and your county extension office can diagnose it.

A weekly routine for checking your lawn

A five-minute check twice a week in warm weather is enough once you know the signs.

1. Pick your gauge spots. Choose one hot spot, such as a slope, a south side or a strip beside pavement, and one ordinary spot, and check both every time.¹
2. Run the checks. Walk across the lawn, look at color and blade shape, and push the screwdriver into both spots.
3. Water within a day of the signs. The best window is 6 to 8 a.m., when pressure is highest, wind is low and evaporation is small. Avoid midday and windy conditions.¹
4. Verify the next day. Use the shovel wedge or screwdriver to confirm moisture at 6 to 8 inches (15 to 20 cm), and adjust the run time if it is not there.¹

Rain resets the clock. Missouri extension says to delay the next irrigation until wilt symptoms return,¹ and a rain gauge shows how much fell. The effective rainfall calculator estimates how much of a storm your lawn can use. After a few weeks, the interval between signs becomes your schedule, and the lawn watering schedule calculator converts it into days and minutes.

Frequently asked questions

Sources

1. Fresenburg, B.S. (2012). Home Lawn Watering Needs. Missouri Environment & Garden. University of Missouri Integrated Pest Management Program.
2. Trenholm, L.E. and Unruh, J.B. Let Your Lawn Tell You When To Water. ENH63. UF/IFAS Extension, University of Florida.
3. UC Statewide IPM Program. How Many Times a Week to Water. The UC Guide to Healthy Lawns. University of California Agriculture and Natural Resources.
4. UC Center for Landscape & Urban Horticulture. Turfgrass Crop Coefficients (Kc). University of California Agriculture and Natural Resources.
5. Allen, R.G., Pereira, L.S., Raes, D. and Smith, M. (1998). Crop Evapotranspiration: Guidelines for Computing Crop Water Requirements. FAO Irrigation and Drainage Paper 56. Food and Agriculture Organization of the United Nations.

Written by Daniel Reeves, PE, CID. Figures in this article were calculated from the cited sources and checked against our lawn watering calculator. Read how we calculate and our editorial policy. Spotted an error? Tell us.