Landscape Architect Articles

LCN Turfcare December 200512-28-05 | News

Mowing Heights

How much or how little to clip doesn?EUR??,,????'???t at first glance seem a worthwhile topic for a column, however, turf experts have quite a bit to say on the subject, including cut ranges for various grasses and climates (see chart).

Mowing a turf at the low end of the height range increases shoot density and a narrower leaf width (finer texture), and, of course, you won?EUR??,,????'???t have to cut again as soon. Cutting low does have disadvantages, though, including less food for root, rhizome and stolon growth.

Everyone seems to agree that mowing is ?EUR??,,????'??stressful?EUR??,,????'?? for the grass, particularly during warmer periods. For these times, increasing the height of cut is advised, as it allows for more root growth and insulates the plant?EUR??,,????'???s base, i.e., whence sprout the shoots.

Why does lower mowing increase stress on turf? The hair on our heads is alive, but doesn?EUR??,,????'???t appear to be particularly stressed from a close cropping. When you cut off more than one-third of the grass?EUR??,,????'??? height, however, you are removing a significant amount of green material that absorbs sunlight and manufactures food (photosynthesis) that gets stored in the root system. Reducing the leaf area lessens the plant’s ability to photosynthesize. Less green means less plant food stored?EUR??,,????'??+rooting is restricted and the turf?EUR??,,????'???s ability to survive stressful periods is reduced.

So, to keep the grass plant from going into shock and parts of the deeper root system from dying, the rule of thumb is not to remove more than one-third of the above ground portion of the grass at one time. This is particularly important during periods of extended high temperature (and drought).

Mowing Tips

Mow your grass regularly. This encourages it to thicken and choke out weeds. Also, make sure your mower blades are sharp. Tests at universities have shown mowing bluegrass with dull blades can make entry wounds for diseases like leaf spot. Shredded grass tips turn brown quickly and look unsightly and reduce lawn quality, shoot density and leaf growth. Tests have also shown mowers with dull blades use 22 percent more gasoline to get the job done than sharper blades.

Not all grass is created equal. Mow at the highest setting recommended for various turf (see chart). The taller the grass blades are above the ground the deeper the root system is below ground. A large, deep network of roots helps grass plants withstand stress during drought and hot weather.

Mow in a different direction every time. Otherwise, grass plants tend to develop a grainy appearance, especially at low mowing heights. Overlap swaths by 2 to 4 inches to achieve a uniform cut.

Wet Turf

Yes, you know not to mow turf when it is wet, but if you do and your blades are a bit dull, it can uproot grass from the soil. Tires on heavier equipment on wet turf tend to compact the soil and impede the movement of air and water into the soil. Of course, during rainy weather, it is better to mow wet grass than to let it get too tall. To avoid overloading the mower engine, cut only a half to three-quarter swath instead of a full width. A better technique is to mow twice, cutting one-half the required height the first pass, then lowering the mower for the second pass. If you mow often enough, the clippings will filter into the grass and don?EUR??,,????'???t need to be removed. Those clippings will return about 25 percent of the required fertilizer to the soil when they decompose. You do need to remove any long clippings atop the turf, as it will block sunlight or encourage disease development when wet.

A half inch of thatch is beneficial. If you have more, use a dethatching machine with vertical blades that slice through soil and kick out thatch debris.