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Archive for Sunday, March 23, 2003

Mowing height can influence spring grass

March 23, 2003

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My itchy, watery eyes and runny nose mean spring has arrived. Soon it will be time to fire up the lawn mower and the trimmer. This time of year, I always hear discussions about two basic lawn care practices: "How low should I mow?" and "should I fertilize my lawn now?" Both practices can have influence how your grass grows this spring.

When mowing, it does not hurt to cut lower than normal the first time or two. In fact, it can help the grass green more quickly because you are removing old leaf tissue that is shading the ground. The soil will warm faster resulting in new grass growth. Be sure to raise the lawn mower to recommended heights after the first mowing to help prevent crabgrass. Crabgrass seeds must have light to germinate, and a high mowing height will shade the soil, helping minimize germination.

Likewise, in upright growing grasses, such as tall fescue and Kentucky bluegrass, rooting depth is influenced by mowing height. The taller the cut, the deeper the roots will grow. A deeper root system means a more drought resistant turf that is stronger.

If your lawn is predominantly tall fescue or Kentucky bluegrass, mow between 1 to 11¼2 inches. For Zoysia grass, mow no higher than an inch. In both cases, be careful not to mow so low that you scalp the turf and damage the crowns. Clippings should be collected and removed from the yard after the first mowing.

After the second mowing, allow clippings to fall to the ground and decompose, especially if you are following the "one-third rule," in which you are only to remove one-third of the grass blade when you mow. The normal mowing height for Kentucky bluegrass is 2 to 3 inches and for tall fescue is 21¼2 to 31¼2 inches. Zoysia grass can be mowed at 2 inches.

To calibrate your lawn mower, place it on a level surface with the motor off and the spark plug disconnected. Reach through the grass discharge shoot and measure from the ground to the blade. Adjust the wheels so the blade is at the desired height. Keep the blade sharp and always practice safe mowing techniques.

What about applying fertilizer now? The answer is: "Do not do it!" Early season fertilizations may cause more problems than they solve. As the soil is slowly warming up, the root system is slowly getting started as well. With this in mind, an application of high nitrogen fertilizer will stimulate green top growth that is out of balance with the root system. Eventually, the tops would need more water and nutrients than the slowly developing root system can supply. A plant is more prone to being damaged by harsh growing conditions and attacked by insects and diseases.

The best time to fertilize cool-season lawns, such as fescue and bluegrass, is after the plant has used stored winter reserves and is ready for more food. That usually occurs in May. At that time, apply the fertilizer at the rate of one pound of nitrogen per 1,000 square feet of lawn. Make sure to water it in well and then be ready to mow.




-- Bruce Chladny is horticulture agent at K-State Research and Extension-Douglas County. For more information, call him at 843-7058 from 8 a.m. to 5 p.m. weekdays.

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