High quality turf will require varying amounts of water depending on the soil type and weather conditions. Heavy clay soils will require more watering than will sandy soils in order for moisture to reach 4-5” down where the grass roots are. However, sandy soil holds less water than clay soil so more frequent watering will be required for lawns in sandy soils. Generally speaking high quality lawn should receive between 1.0-1.5” of water per week. So if it rains an inch that week, there’s no need to water in the cool spring and fall weather. However, in the hot months, turf needs watering badly to keep its vigor and continue looking good. Watering at least 1.5” per week in July and August will ensure your lawn doesn’t dry out. Heat and drought stress will cause cool season grasses to go dormant, meaning they allow all of their leaves to die off to conserve energy and won’t start growing new shoots until wetter and cooler conditions come back in the fall. Watering more often works best in the hot summer months, meaning watering ½” 3 times a week is better than watering 1.5” once a week. This is because watering also provides the benefits of cooling down heat stressed turf which helps it get through the stress caused by the heat of the summer.

If you’re interested in more information on irrigation systems and the myths of when to water, visit our blog post “5 Minnesota Irrigation Myths Busted” .

For those of you working the hose (manual irrigation system, haha) to keep your lawn green, let’s do the math to see how you can make sure your lawn is getting the 1.0 – 1.5” per week it needs. The average flow rate in Minneapolis and St. Paul MN is roughly 10 gallons per minute. You can find out precisely what your flow rate is by turning your hose spigot on full blast and using a stopwatch to determine how many seconds it takes to fill up a 1 gallon milk container. Then convert that reading into gallons per minute, for example if it takes 6 seconds to fill a 1 gallon container, than your flow rate equals 10 gallons per minute. We do this test before we install every sprinkler system to ensure the system works properly.

Average flow rate from hose spigot in Minneapolis = 10 gallons per minute (can vary between 8-18 gallons per minute).

Let’s assume your lawn is exactly 6,000 square feet for this example.

1/2 “ of water per square foot = 0.0416 square feet of water.

Multiply that square feet of water times the area of your lawn to give you the amount of gallons you would need. The amount of water needed to cover a 6,000 square foot lawn with ½” of water = 6,000 x 0.0416 = 250 gallons.

Using a flow rate of 10 gallons per minute, you will need to water for about 25 minutes to give your lawn a ½” of water or 50 minutes to water apply 1” of water per square foot.

Don’t forget to move your hose around the yard to ensure all the grass is covered!

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