Kentucky Bluegrass Watering Guide
Kentucky bluegrass needs more water than most lawn grasses to stay green, yet it survives drought by going dormant. This guide gives the weekly inches, days between waterings and minutes per run for each case.
By Daniel Reeves, PE, CID
Irrigation Design Engineer
Short answer
Water Kentucky bluegrass about 1 to 1.5 inches (25 to 38 mm) a week in summer, split into 2 or 3 deep waterings, and cut back in spring and fall.
Kentucky bluegrass watering also depends on soil: in hot weather sandy soil needs water every 1 to 1.5 days, loam and clay every 2 to 3 days. Each watering should wet the top 6 to 8 inches. A dormant lawn survives on ¼ inch every two weeks to ½ inch a week.
The grass type water needs calculator compares weekly needs by species, but extension advice for bluegrass looks contradictory. Kansas State suggests ½ inch three times a week in midsummer,1 Nebraska says 1 to 1.5 inches a week,2 and a dormant lawn needs almost nothing for weeks.1 Each is right for its conditions, and this guide shows how the numbers are built.
Below are weekly totals, days between waterings by soil, a worked schedule that ends in minutes on your controller, dormancy amounts, and the rules for new seed and sod.
Key takeaways
- Kentucky bluegrass needs about 1 to 1.5 inches (25 to 38 mm) a week in July and August, from rain and irrigation combined.
- Split the total into 2 or 3 deep waterings. Kansas State's midsummer rule is ½ inch three times a week.
- In a hot summer, loam and clay need water every 2 to 3 days and loamy sand every 1 to 1.5 days.
- A dormant lawn needs ¼ inch every two weeks to ½ inch a week to keep its crowns alive.
- New seed needs light watering every day, up to four times a day, until it germinates in 14 to 21 days.
- Most soils absorb about ½ inch an hour, so stop a run when water starts to run off and finish later.
How much water does Kentucky bluegrass need per week?
Nebraska Extension puts turfgrass at 1 to 1.5 inches (25 to 38 mm) of water a week in July and August to stay green and growing.2 Kansas State says bluegrass needs about 1½ inches (38 mm) a week in hot weather to stay green all summer, and less in spring and fall.3 Missouri Extension lists 1.2 inches (30 mm) for green bluegrass, more than tall fescue, zoysia or Bermuda.4
Weekly lawn water requirement by grass, green versus dormant
| Grass | Green turf, in/week (mm) | Dormant turf, in/week (mm) |
|---|---|---|
| Perennial ryegrass | 1.5 (38) | 1.0 (25) |
| Kentucky bluegrass | 1.2 (30) | 0.7 (18) |
| Tall fescue | 0.8 (20) | 0.5 (13) |
| Zoysia or Bermuda | 0.5 (13) | 0.2 (5) |
| Buffalograss | 0.3 (8) | 0.2 (5) |
Source: University of Missouri Extension.4 Green turf stays green and growing; dormant turf may turn brown but survives. Missouri's dormant figure is higher than the Kansas and Nebraska dormancy amounts shown below.
These totals come from evapotranspiration (ETo) times a crop coefficient (Kc). The University of California turf table counts Kentucky bluegrass among its cool-season grasses, averages a Kc of 0.80 over the year and runs 0.86 to 0.95 from May through August.5 A July week with 1.5 inches of ETo therefore needs about 1.4 inches. The lawn water requirement calculator does this with your local ET, and the lawn watering by grass type chart lists other species.
How often should you water Kentucky bluegrass?
Because cool-season roots recede in hot weather, Kansas State says bluegrass may need ½ inch three times a week in midsummer, and that established lawns should not need daily watering.1 Nebraska suggests two or at most three weekly applications on clay soil and more frequent ones on sand.2
Frequency is the weekly total divided by what the root zone can take back per watering, and soil sets that limit.6 The table assumes roots in the top 6 inches, a refill when half the plant-available water is gone, and bluegrass use of 0.14 inch a day in a typical summer and 0.21 inch a day in a hot one, about 1 and 1.5 inches a week.
Days between waterings for Kentucky bluegrass, by soil and weather
| Soil | Plant-available water per foot | Refill per watering (top 6 in) | Typical summer (0.14 in/day) | Hot summer (0.21 in/day) |
|---|---|---|---|---|
| Loamy sand and sand | 0.75–1.25 in (19–32 mm) | 0.19–0.31 in (5–8 mm) | Every 1.5–2 days | Every 1–1.5 days |
| Sandy loam | 1.25–1.75 in (32–44 mm) | 0.31–0.44 in (8–11 mm) | Every 2–3 days | Every 1.5–2 days |
| Loam and silt loam | 1.50–2.30 in (38–58 mm) | 0.38–0.58 in (10–15 mm) | Every 2.5–4 days | Every 2–3 days |
| Clay loam and clay | 1.60–2.50 in (41–64 mm) | 0.40–0.63 in (10–16 mm) | Every 3–4.5 days | Every 2–3 days |
Water-holding ranges from UC Center for Landscape & Urban Horticulture.6 Refill = 0.5 ft × water per foot × 0.5. Days = refill ÷ daily use, rounded to the nearest half day. No rain, uniformity ignored.
The table shows what soil holds, not how fast it absorbs. Missouri notes that most of its soils take in only about ½ inch an hour, so stop a run when water begins to run off and resume after it soaks in.4 The cycle and soak calculator splits a run into cycles, and the available water capacity calculator estimates what your own soil holds.
How to build a Kentucky bluegrass watering schedule
Four steps turn the weekly total into minutes per zone.
Formula
Waterings per week = (ETo × Kc − rain) ÷ (root depth × water per foot × 0.5), rounded up
ETo and rain are weekly inches, root depth is in feet and water per foot is in inches per foot. Minutes per watering = inches per watering ÷ DU ÷ precipitation rate (in/hr) × 60, where DU is distribution uniformity as a decimal.
- Find weekly use. Multiply weekly ETo by Kc, which is 0.80 as a yearly average and 0.94 for July, then subtract the rain that soaked in.
- Find the refill depth. Multiply a 0.5 ft root zone by your soil's plant-available water and by 0.5. The irrigation interval calculator turns refill depth and daily use into days between waterings.
- Divide and round up. Weekly use divided by refill depth gives waterings per week. Space them evenly and keep each one within what the soil absorbs.
- Convert to minutes. Run a catch-can test: set straight-sided cans around the sprinkler, run it for a timed period and read the depth.4 Enter the rate in the how long to water lawn calculator, or let the lawn watering schedule calculator run all four steps.
Tip: mow high to stretch the interval
Kansas State recommends mowing bluegrass at 2 to 3 inches because root growth follows shoot growth, so taller grass roots deeper and handles heat and drought better.3 Nebraska suggests 2.5 to 3 inches.2
Pick your grass type and climate. The calculator returns the weekly water need to plan from.
Worked example: Kentucky bluegrass on silt loam in July
Take a 4,000 sq ft bluegrass lawn on silt loam in July. ETo averages 0.22 inch a day, no rain falls, rotors apply 0.5 inch an hour, and DU is an untested 0.7.
- Weekly ETo0.22 in/day × 7 = 1.54 in
- Bluegrass water use (July Kc 0.94)1.54 × 0.94 = 1.45 in
- Refill depth (6 in roots, 2.0 in/ft)0.5 ft × 2.0 in/ft × 0.5 = 0.50 in
- Waterings per week1.45 ÷ 0.50 = 2.9, round up to 3
- Water to apply per week1.45 ÷ 0.7 = 2.07 in
- Water per watering2.07 ÷ 3 = 0.69 in
- Minutes per watering0.69 ÷ 0.5 × 60 = 83 min
- Weekly volume4,000 sq ft × 2.07 in × 0.624 ≈ 5,170 gal
3 waterings a week, about 83 minutes each
Space them every 2 to 3 days. Metric: 1.45 in is 37 mm of use, 2.07 in is 53 mm applied, 0.69 in is 18 mm per watering, and the weekly volume is about 19,500 liters over 372 m².
Each watering puts 0.48 inch (0.69 × 0.7) into the root zone, just under the 0.50 inch the soil can take back. The result also matches Kansas State's ½ inch three times a week.1 Because 0.69 inch at 0.5 in/hr is near the absorption limit, run it as two cycles of about 41 minutes an hour apart.
How to water in spring, fall and summer dormancy
In spring, wait. Kansas State advises against early irrigation because cool weather lowers demand and unneeded water encourages shallow roots. Start when the lawn shows stress, then wet the soil to 6 to 8 inches, which takes 1 to 1.5 inches depending on soil.1
In fall the lawn needs less than in summer, and September is the best month to seed bluegrass, with sod working best in September or October.3 UC's Kc falls from 0.94 in July to 0.75 in October, about 20 percent lower before ETo itself drops,5 so a controller left on its July program overwaters. The seasonal adjustment calculator gives a percentage for each month. If fall is dry, water thoroughly once before the ground freezes.1
Summer dormancy
Bluegrass survives a hot, dry spell by going dormant. Kansas State calls it a water-saving grass if allowed to go brown.3 The sources differ on how much water keeps the crowns alive.
Water for a dormant Kentucky bluegrass lawn, by source
| Source | Amount | Per week, in (mm) |
|---|---|---|
| Kansas State | ¼ in (6 mm) every couple of weeks, after 2–3 weeks without water | About 0.13 (3) |
| Nebraska Extension | ½ in (13 mm) a week, starting after three weeks without rain | 0.5 (13) |
| Missouri Extension | At least 1 in (25 mm) every two or three weeks | 0.33–0.5 (8–13) |
Sources: Kansas State,1 Nebraska Extension2 and Missouri Extension.4
Start at the low end for a healthy lawn on good soil and raise the amount as the dry spell lengthens. Kansas State says established bluegrass can survive up to 8 weeks this way,1 but Missouri warns that dormancy does not guarantee full recovery.4 Keep traffic and mowing off dormant turf, and water deeply in mid to late August to revive it before fall work.12
How to water new Kentucky bluegrass seed and sod
New seed
Bluegrass is slow to start: constantly moist seed germinates in 14 to 21 days, depending on soil temperature.3 Missouri keeps the top 1 to 2 inches moist but not saturated until germination, using 1/8 to ¼ inch of water one to four times a day. It then reduces frequency once seedlings reach 2 inches and switches to deep, infrequent watering after two or three mowings.4 A straw cover slows drying.4 The grass seed watering calculator gives a day-by-day taper.
New sod
Water new sod one or two times a day from the day it is laid. The first watering takes about 1 inch to wet the sod and the top inch of soil beneath it, and lifting a corner confirms it.4 Switch to deep, infrequent watering after two or three mowings. Spring-laid sod needs closer watching in summer dry spells because its roots are less developed.3 The sod watering calculator sets the schedule.
Signs your Kentucky bluegrass needs water, or has had enough
The calendar sets the starting point and the lawn corrects it. Kansas State names a bluish cast and lingering footprints as the cue to water.3
Water now
- Blades turn dull blue-green or bluish-purple.
- Footprints stay visible for hours.
- Leaves fold or roll lengthwise.
- A probe stops in dry soil above the 6- to 8-inch root zone.
Hold off
- Grass springs upright after you walk on it.
- A probe slides easily to 6 to 8 inches.
- Squeezed soil from the root zone drips water.
- Footprints are squashy, or water runs onto pavement.
Missouri Extension is the source for these checks.4 Hot spots such as south-facing slopes, hard soil and edges beside driveways wilt first, so hand-water them to delay running the whole lawn.4
Caution: wet wilt
Blades that curl on a hot afternoon over soil that is still wet are not asking for water. Missouri calls this wet wilt, and extra water only starves a shallow root zone of oxygen.4
Water early, roughly 4 to 10 a.m., when wind and evaporation are lowest.24 Rain counts toward the weekly total, and Kansas State suggests pausing the timer when rainfall is adequate.1 The effective rainfall calculator estimates how much of a storm your lawn can use. Local watering-day limits override any schedule here: apply the weekly total across the days allowed.
Frequently asked questions
Is it okay to water Kentucky bluegrass every day?
Not once it is established. Kansas State says daily watering of established lawns should be neither necessary nor desirable, and Nebraska warns that 10 to 15 minutes every day keeps a shallow layer of soil wet and starves roots of oxygen. New seed and new sod are the exceptions and do need daily watering until they root.
Is 1 inch of water per week enough for Kentucky bluegrass?
It is the low end of the range. One inch covers a mild week, but Missouri Extension lists 1.2 inches for green bluegrass, Nebraska gives 1 to 1.5 inches, and Kansas State puts hot weather at about 1.5 inches. Rain counts toward the total. On sandy soil or in a heat wave, plan on the upper end.
How long can Kentucky bluegrass go without water?
Kansas State says a dormant lawn can go two to three weeks or more without water, then needs about ¼ inch every couple of weeks. Established bluegrass on good soil, maintained properly, can survive up to 8 weeks without substantial irrigation. Recovery is not guaranteed, so shorten the gap in extreme heat.
Will brown Kentucky bluegrass turn green again?
Usually, if the crowns are alive. Missouri Extension says thorough watering brings a dormant lawn back and new growth resumes from the crown, but dormancy does not guarantee full recovery. Cooler weather and rain help. Reseed any bare areas in September, the best month to seed bluegrass.
How many gallons does Kentucky bluegrass need per 1,000 square feet?
One inch of water on 1,000 square feet takes 624 gallons (2,360 liters). At 1 inch a week that is 624 gallons, and at 1.5 inches it is 936 gallons (3,540 liters). Rain delivers the same volume for free, so subtract what a rain gauge measured before you run the sprinklers.
Does Kentucky bluegrass need more water than tall fescue?
Yes. Missouri Extension lists 1.2 inches a week for green Kentucky bluegrass and 0.8 inch for tall fescue, about 1.5 times as much. Nebraska Extension says tall fescue has a much larger root system, so it can draw most of the water it needs from deeper soil, while bluegrass relies on dormancy to survive drought.
Sources
- Nolting, E., Upham, W. and Sell, P. (2008). Watering Established Lawns. MF-2803. Kansas State University Agricultural Experiment Station and Cooperative Extension Service.
- Nebraska Extension. Smart Summer Watering. University of Nebraska–Lincoln.
- K-State Research and Extension, Ford County. Kentucky Bluegrass Lawns. Kansas State University.
- University of Missouri Extension. Home Lawn Watering Guide. Publication G6720.
- UC Agriculture and Natural Resources. Turfgrass Crop Coefficients (Kc). Water Use of Turfgrass and Landscape Plant Materials.
- UC Center for Landscape & Urban Horticulture. Soil Water Holding Characteristics. University of California Agriculture and Natural Resources. Adapted from Schwankl and Prichard (2009).
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.