Tall Fescue Watering Guide

The lawn watering schedule calculator returns days and minutes for your yard, and this guide shows the method behind it. Tall fescue is forgiving, which also makes it easy to overwater: a lawn on two deep waterings a week can look better than one on seven short ones, and the right split changes with soil, sprinkler and weather.

Below you will find weekly inch targets by weather, how often to water by season and soil, a worked example that ends in minutes on your controller, and the rules for new seed, new sod and summer dormancy. Every figure comes from university extension or UC research, listed at the end.

How much water does tall fescue need per week?

Start with the weekly total, then split it. Tall fescue is the reference crop that evapotranspiration (ET) is measured against, yet turfgrass needs less water than reference ET (ETo) to look acceptable through most of the year.¹ The adjustment is a crop coefficient (Kc). UC's cool-season turf values, which include tall fescue, run from 0.60 in December to 1.04 in April and average 0.80 over the year.¹ Weekly need is weekly ETo multiplied by Kc, and the evapotranspiration calculator helps you work out ETo.

Extension guidance lands in the same range without ET math. Clemson puts tall fescue at about 1 to 1.25 inches a week, enough to wet the soil 4 to 6 inches,² and K-State says midsummer can call for 0.75 inch twice a week, or 1.5 inches in total.³ Table 1 turns four weather types into weekly totals.

Weekly tall fescue water need from ETo and crop coefficient

Daily ETo values are planning figures; use your own weather station. Weekly need is weekly ETo × Kc, before rain. UC's monthly Kc for cool-season turf, developed in California, so treat it as approximate elsewhere: Jan 0.61, Feb 0.64, Mar 0.75, Apr 1.04, May 0.95, Jun 0.88, Jul 0.94, Aug 0.86, Sep 0.74, Oct 0.75, Nov 0.69, Dec 0.60.¹

Rain counts toward these totals. An inch of water over 1,000 sq ft is 623 gallons (2,360 liters), so a lawn using 1.2 inches a week needs about 750 gallons (2,830 liters) per 1,000 sq ft. The lawn water requirement calculator returns your own weekly figure from local ET.

To compare other grasses, use the grass type water needs calculator or the lawn watering by grass type chart.

Tall fescue watering schedule by season

Frequency follows the weather because ET does. Spring needs the least attention: K-State advises against watering established tall fescue early in spring, because moisture left from winter covers cool weather and unnecessary irrigation can lead to a shallow root system.³ Wait for stress signs, then water deeply.

Summer is when the schedule matters. UC Riverside irrigated tall fescue at 80 to 85 percent of reference ET and found that 2 waterings a week gave better color and quality than 3 or 4.⁴ K-State adds that cool-season roots recede in hot weather, so 0.75 inch twice a week may be needed in midsummer.³ Table 2 compares the published figures.

Published tall fescue irrigation guidance for summer

Sources 2, 3 and 4. Clemson and K-State give totals for home lawns; the UC Riverside trial held the weekly total equal and changed only the frequency.

In fall, follow the falling ETo. The October row of Table 1 needs about half an inch a week, and K-State notes that roots grow deeper in spring and fall than in midsummer.³ The seasonal adjustment calculator shows what percentage of your summer run time to use each month, and the effective rainfall calculator estimates how much of a storm your lawn can use. Pause the timer when rain has covered a watering.³

How soil and root depth set the days between waterings

Soil is the tank and roots draw from it. K-State's target is to moisten the soil 6 to 8 inches deep, which takes 1 to 1.5 inches of water depending on soil type. On level ground with good soil you can apply that in one watering, as long as the sprinkler does not apply water faster than the soil absorbs it. Puddled water can heat up enough on hot days to scald the grass.³ In midsummer, when roots recede, the K-State figure drops to 0.75 inch per watering.³

Sandy soil holds less and needs shorter, closer waterings, such as 0.5 to 0.75 inch every 3 days.² Slopes need the depth applied in increments, and heavy clay absorbs slowly.^{3 6} K-State's aim is to moisten the root zone within a 24-hour period, then let the soil dry before the next watering. The cycle and soak calculator sets the run length per cycle, and the available water capacity calculator estimates what your own soil holds.

Deep roots are why tall fescue tolerates fewer waterings. In the UC Riverside trial, plots watered twice a week held significantly more soil water at 24 and 36 inches than plots watered 3 or 4 times, which UC notes would also benefit trees and other deep-rooted plants growing with the turf.⁴

How to build your watering schedule

The method needs five inputs: weekly ETo, the month's Kc, rain, sprinkler uniformity and precipitation rate.

1. Find the weekly need. Multiply weekly ETo by the month's Kc from the note under Table 1, then subtract rain that soaked in.
2. Choose the waterings. Pick 2, 3, or one every third day from the soil rules above, and divide the weekly total by that number.
3. Correct for uneven coverage. Divide by DU. Use your tested value, or the assumed 0.75 from the example below if you have not tested.
4. Convert to minutes. Divide the depth per watering by your precipitation rate and multiply by 60. Measure the rate with a catch-can test, then let the how long to water lawn calculator convert inches to minutes per zone.

Worked example: a 4,000 sq ft lawn in August

Take a 4,000 sq ft tall fescue lawn on loam in a hot, humid August week. ETo averages 0.20 inch a day, no rain falls, rotors apply 0.5 inch an hour, and distribution uniformity is an assumed 0.75.

1. Weekly ETo0.20 in/day × 7 = 1.40 in
2. Weekly need (August Kc 0.86)1.40 × 0.86 = 1.20 in
3. Water to apply1.20 ÷ 0.75 = 1.60 in
4. Waterings per week (loam)2
5. Water per watering1.60 ÷ 2 = 0.80 in
6. Minutes per watering0.80 ÷ 0.5 × 60 = 96 min
7. Weekly volume4,000 × 1.60 × 0.623 ≈ 3,990 gal

2 waterings a week, about 96 minutes each

Space them 3 to 4 days apart. Metric: 1.60 in is 41 mm a week, 20 mm per watering, or about 15,100 liters over 372 m².

Check the result against the guidance. A weekly use of 1.20 inches is inside Clemson's 1 to 1.25 inches and just below K-State's midsummer 1.5 inches.^{2 3} If 96 minutes at 0.5 inch an hour causes runoff on your soil, run two 48-minute cycles and let the first soak in.

How to water new tall fescue seed and sod

Timing helps as much as water. UGA calls September and October the ideal months for tall fescue,⁵ and K-State names September best for cool-season grasses.⁶

After seeding, keep the upper 1 to 2 inches of soil moist, not wet. That usually means about 0.10 to 0.25 inch (3 to 6 mm) a day for the first three weeks. Under good conditions seed germinates in 5 to 10 days and is ready for a first mowing in 2 to 3 weeks.⁵ Seed that starts to germinate and then dries out may die, so use light waterings once or twice a day, or more, as needed.⁶

Watering taper for new tall fescue seed

Sources 5 and 6. Measure depth in straight-sided cans. Rain can replace a watering.

Water new sod like new seed: often enough to keep the area between the sod and the soil moist until roots knit in, then lengthen the interval. Both seeded and sodded tall fescue need regular watering through their first summer.⁶ The grass seed watering calculator and sod watering calculator turn these rules into a day-by-day plan.

What to do when tall fescue goes dormant in summer

Under drought stress an established lawn can go dormant, turning tan while the crowns stay alive. K-State says a dormant lawn may go two to three weeks or more without water, then needs about 0.25 inch every couple of weeks, and that established fescue on good soil handled this way can survive up to 8 weeks without substantial irrigation.³ Clemson puts the figure at about 0.5 inch every 3 weeks.²

The lawn K-State describes is established, growing in good soil and eased into summer gradually. K-State also suggests watering a dormant lawn deeply in mid to late August, so it can respond to fall fertilizing, aeration and overseeding.³

Signs tall fescue needs water now

The calendar sets the starting point and the lawn corrects it. K-State's stress signs are a dull blue-green color and footprints that stay pressed down after you walk across the grass.³

Frequently asked questions

Sources

1. UC Center for Landscape & Urban Horticulture. Turfgrass Crop Coefficients (Kc). University of California Agriculture and Natural Resources. Values from Meyer et al. (1985).
2. Clemson Cooperative Extension Home & Garden Information Center. Tall Fescue Maintenance Calendar. Clemson University.
3. Nolting, E., Upham, W. and Sell, P. (2008). Watering Established Lawns. MF-2803. Kansas State University Research and Extension.
4. UCR Turfgrass Research. Influence of irrigation scheduling on tall fescue performance. Accumulative Research Summary (2006), Section A, Project 1. University of California, Riverside.
5. University of Georgia Cooperative Extension. September and October are perfect for seeding tall fescue lawns. UGA College of Agricultural and Environmental Sciences.
6. Upham, W., Nolting, E. and Sell, P. (2008). Watering New Lawns. MF-2802. Kansas State University Research and Extension.

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.