The plentiful rain and cool temperatures that eastern Nebraska has received this spring and early summer have been ideal for the growth of cool season grasses like Kentucky bluegrass and tall fescue, resulting in lawns that are growing vigorously. It is important during this time of very active turf growth, and as we move into hotter, drier weather, to keep a few important management techniques in mind ensuring that your lawn will be beautiful and healthy throughout the challenging months of July and August.
Grass that is growing quickly requires frequent mowing. Many homeowners develop the habit of mowing their lawn once a week during spring, summer and fall. This schedule is fine during periods of slower summer growth, however, it is often not frequent enough when grass is growing very fast. No more than one-third of the grass plant's height should be removed at one mowing.
For example, if a turf is normally mowed at a height of 3 inches, then it's time to mow when the canopy reaches a height of 4.5 inches. In this case, removing 1.5 inches is equal to one-third of the grass canopy's total height.
Generally, mowing is required twice per week in the spring, April through early June; once per week in the summer, mid-June through early September; and one and a half times per week in the fall.
However if, in our example above, the turf grew 2 or 2.5 inches in a week's time, than mowing at 3 inches would result in scalping. Scalping occurs when more than one-third of the turf's foliage is removed at one time, often exposing the stems of the grass plants, resulting in stress and even plant death.
Removal of 50% or more of the turf canopy at one mowing results in severe defoliation. At this point, existing root and rhizome growth stops, and the initiation of new tillers, roots and rhizomes stops. The plant's energy reserves are redirected to development of new leaf or shoot growth, at the expense of the root development. Development of a deep, healthy root system, which endows the grass with better disease and drought resistance in the hot, dry months of July and August, is the goal of all turf managers, and anything that slows root development should be avoided.
Bagging vs. Mulching
Ideally, mowing is done frequently enough that clippings can be left on the lawn. Clippings returned to the turf can contribute up to 1 lb. Nitrogen/1,000 sq.ft. over the course of a summer, and will not contribute to the development of thatch. However, if more than one-third of the grass height must be removed at one time, there will be a lot of clippings, so the clippings should be bagged and removed. Heavy clippings, if left on the lawn, will cause damage through light exclusion, resulting in yellowing and thinning of the turf. Heavy clippings left on the lawn can also encourage disease problems.
If you must mow a lawn that has gotten too tall, if for instance you left on vacation for a few days, after returning raise the height of your mower to remove only one-third of the grasses' present height. Then after 2-3 days, mow again, lowering the height to your normal level.