For Release May 9, 2004
Mowing and Watering Management Crucial in Your Lawn
by Chuck Otte, Geary County Extension Agent
With the weather last week heating up like it did, it really drives home the point that how you mow your lawn and how you water your lawn are probably the two strongest considerations for how your lawn will survive the Kansas summer. Let me clarify one point though. You don't have to water your tall fescue or bluegrass lawn to keep it alive. If the weather turns hot and dry, both of these grasses will want to go dormant and it's okay to let them do so. If the weather stays hot and dry for a long time, you may need to give the lawn one deep soaking every month to keep the crowns from drying out.
There are two basic principles to keep in mind with your lawns. Create deep roots and keep the ground shaded. Both of these principles are accomplished with a single action, mowing tall. Root length in your turfgrass is directly related to leaf blade length. The longer the leaf blades, the deeper the roots. You want a deeply rooted turf because it can access more soil moisture allowing it to be better able to tolerate dry hot weather.
How tall is tall? For fescue lawns, even the new varieties, three and one half inches would be my preferred height. For bluegrass, three inches is a minimum. Okay, how often should you mow? Mowing should not be attempted by the calendar, it should be done by the amount of growth. Never take off more than one third the total height of the grass. If you wait until your grass is six inches tall, you should only cut off two inches of leaf blade. So with a three inch cutting height on bluegrass, you should mow before the grass gets taller than four and one half inches.
If you let the grass get quite tall and then mow it real short, it is a shock to the plant and can cause root death (eliminating the desire for deep rooting), it can open up bare ground to the sun (creating a great opportunity for weeds to get started) and it just plain looks bad because of all those pale leaf blades and crowns you expose. Can you mow too often? As long as you are cutting at the desired height and not running the mower on drought stressed grass, no, you can't mow too often. It's also very important to keep the lawn mower blade sharp to get a clean cut rather than a ragged tear. A clean cut will lose less water from the plant.
If you want to water your lawn to keep it from going dormant, then do it right. The right way to water is infrequently and deep. Watering once to twice a week and making sure that you wet the soil down at least six inches when you do water is your goal. I can't tell you how long to run your sprinkler, you'll have to figure that out yourself. But you'll need to apply about an inch of water to your lawn to soak up six inches of soil. You may have to run it through the cycle several times so you don't get excessive runoff, but place a rain gauge in your lawn to find out how much you are applying.
What you do not want to do is water the lawn just a little bit every day. This wastes water and concentrates the moisture in the soil surface, and that is where all your grass roots will be, not the deep rooting plan we are striving for. Finally, apply your lawn irrigation as early in the day as possible when it is coolest, calmest and highest humidity. This also minimizes lawn disease risk. Do not water in the afternoon and evening. You don't do the grass any favor and you waste a lot of water. Lawns can survive Kansas summers, but they need your help to do so!
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