How to Mow and Water a Lawn in Oklahoma

Most lawn problems we get called about are not treatment problems. They are mowing and watering problems, and the fix is free. Here is what the two grasses in the Oklahoma City metro actually want.

How high to mow

Bermuda likes it low. Mow at 1.5 inches or less for best results and keep it there through the season. Low mowing keeps Bermuda dense, and dense turf is the best weed control there is, because there is no room for weeds. Fescue is the opposite: mow it at 3 inches, because the height shades the soil and protects the crown in summer heat.

If you do not know which you have, look at it in January. Bermuda goes tan and dormant after the first hard freeze; fescue stays green through most of the winter.

How often, and how much

Weekly during the growing season, and never remove more than about a third of the blade at once. Scalping a lawn that got away from you stresses it and opens the ground to weeds, so if it is tall, take it down over two mows rather than one.

Mulch, do not bag. Clippings are mostly water, they break down quickly, and they return nitrogen to the soil. The one time to bag is when the lawn got away from you and you cannot follow the one-third rule: cutting a tall lawn and leaving the clumps builds thatch. Bag that mow, get the height back under control, and go back to mulching.

Sharpen the blade twice a season. A dull blade tears the leaf instead of cutting it; the torn tips brown out and the lawn looks pale a day after mowing, which gets blamed on the treatment. Torn tips also open the leaf to fungus.

Mowing after a treatment

After liquid weed control or pre-emergent, wait 24 hours so the product stays on the leaf long enough to move into the plant. After fertilizer or Soil Conditioning, mowing is fine once it is dry. After aeration, mow as normal. After overseeding, wait until the new grass is up and rooted, because mowing earlier pulls the seedlings out. Mulch in every one of these cases.

In fall, keep Bermuda mowed low until it stops growing. Bermuda that goes into winter short and clean comes out of dormancy faster. Fescue stays at its normal height.

How much to water

Deeply and infrequently, early in the morning. In hot, dry conditions Bermuda needs about 1 to 1.5 inches a week and fescue about 1.5 to 2, counting rainfall. Deep watering once or twice a week grows deep roots. A little every day, or every other day, creates weed problems, shallow roots and thin areas. It is the single worst thing you can do to a lawn, and it is the default setting on most sprinkler timers.

To find out what an inch looks like on your system, set an empty tuna can on the lawn and run the sprinklers until it fills to about an inch to an inch and a half. That is how long each zone needs, and it is usually an hour or more.

Why early morning: less wind, less evaporation, and the grass is dry by midday. Evening watering leaves the lawn wet overnight, which is how fungus starts.

The sod company set my timer

Almost certainly wrong for an established lawn. Sod companies set timers to ten minutes a day or every other day, because that is what gets new sod to knit down. That setting should have been changed about two weeks after the sod took. Left alone, it grows a lawn with shallow roots that cannot handle July. Change it to deep, infrequent watering and the lawn will root properly.

Watering after a treatment

Fertilizer and gypsum: yes, on the normal schedule; it moves the product into the soil. Pre-emergent: rain or watering activates it, and there is nothing you need to do the day of. Liquid weed control and Soil Conditioning: give it 24 hours first. The weed control surfactant is rain resistant in about 30 minutes short of a downpour, but a day of patience makes sure nothing washes off before it has worked.

Winter, drought and restrictions

Bermuda is dormant and brown in winter, and that is normal. It still needs water about twice a month in a dry winter, and a deep watering a day or two before a hard freeze protects the roots. Fescue stays green and keeps using water, so it gets a deep drink any week without rain, on a day above freezing and early enough to soak in before night.

In a drought, a Bermuda lawn will go dormant and brown and green back up when water returns. It is not dead. Fescue does not have that trick and will thin out. Under watering restrictions, water deeply on the day you are allowed to rather than spreading the allowance thin.

New seed is the exception

Different rules. Keep seeded areas consistently moist until sprouting, which means short, frequent watering for the first couple of weeks. Once the grass is up, gradually water less often and more deeply until it is established, then put it on the normal schedule. Dry soil during germination is seed that never comes up.