Published: May 12, 2008 09:43 pm         

Frequent mowing important to ensure a healthy lawn

Growing Things column

Lawn mowing requires more time than all other operations involved in maintaining a high-quality lawn. Bagging and removing grass clippings just adds to the time and drudgery involved in the mowing operation.

It must be clearly understood that improper mowing can have damaging effects on both the health and quality of the lawn. The two most important aspects of mowing are proper mowing height and proper mowing frequency.

Mowing height

Selecting the correct mowing height depends primarily upon the species of grass in the lawn. The appropriate cutting heights for the common lawn grasses found in West Virginia are listed below.

- Kentucky bluegrass, 1 1?2” - 2 1?2”

- Fine Fescue, 2” - 2 1?2”

- Perennial Ryegrass, 2” - 2 1?2”

- Tall Fescue, 2 1?2” - 3”

- Zoysiagrass, 1?2” - 1”

- Bermudagrass, 1?2” - 1”

Lawn grasses, like most other plants, must manufacture food through the process of photosynthesis if they are to survive and grow. This process occurs mainly in the leaves of the plant. Typically, the more leaf area, the more food produced. Grasses cut at low mowing heights cannot sustain the rate of photosynthesis necessary to produce enough food to maintain a healthy plant because of a low leaf area.

The short mowing height weakens the grass and increases its susceptibility to weed invasion, disease and injury from drought and summer heat. Higher mowing heights favor deeper grass roots, a greater number of roots and an overall healthier grass plant. The deeper, more prolific root system increases the capability of the grass to acquire soil, water and nutrients. This, in turn, makes lawn maintenance easier.

It is advisable to raise the cutting height of the lawn slightly (by 1?2” plus) in the summer to provide more shade to the lower portion of the grass plant and soil to reduce heat stress and, also, to increase the leaf area available for food production.

Mowing frequency

Mowing frequency is extremely important to ensure a healthy lawn and reduce the accumulation of clipping debris on the lawn surface.

The homeowner should never remove more than one-third of the total leaf surface at any one mowing. For example, if the selected mowing height is 2 inches, the grass should not grow to more than 3 inches before it is mowed.

Removing more than one-third of the leaf surface at one time results in an open, stemmy appearance of the lawn, weakens the grass plant, reduces or stops root growth, and leaves significant clipping debris on the lawn surface. Clipping debris is not only unsightly as it dries on the lawn surface, but it also excludes light from the grass, further reducing its health. Mowing will normally be required more often in the spring and fall with a frequency of at least once every week.

Other mowing considerations

Mow lawns when dry so clippings will not clump together on the surface of the lawn.

There will be periods of time in which prolonged rain makes it impossible to mow grass regularly. The longer clippings resulting from an infrequent mowing can still remain on the lawn if the clumps of grass are spread out evenly over the lawn to allow them to readily decompose, or if the clippings are allowed to dry for a day or two, then mowed again to distribute them evenly.

If for any reason the quantity of clippings is too great to leave on the lawn, remove and distribute them around trees and shrubs as a mulch. Grass clippings can also be composted.

Mowers

Any lawn mower can be used to return grass clippings to the lawn. Rear-bagging mowers normally have a discharge door that can be closed when the bag is not in use to eliminate clippings and other debris from flying at the operator. Also available are accessory attachments for most mowers to seal off or close the discharge openings or ports. Side discharge mowers can simply return clippings by leaving the port open. Check with your local dealer.

Mulching mowers are designed to recycle (recut) clippings underneath the mower housing, resulting in clippings being cut into smaller pieces. These smaller pieces sift down into the lawn more readily than with nonmulching mowers and reduce clipping debris on the lawn surface.

Grass clippings contain valuable nutrients that can generate up to 25 percent of your lawn’s total fertilizer needs. A hundred pounds of grass clippings can generate and recycle as much as 3 to 4 pounds of nitrogen, one-half to 1 pound of phosphorus, and 2 to 3 pounds of potassium back to the lawn. These are the three most important nutrients needed by lawns and commonly supplied in lawn fertilizers. The other good news is that grass clippings do not contribute to thatch (an organic debris layer between the soil and live grass) since grass clippings are 75 percent to 85 percent water and decompose readily.

Why, then, do many homeowners bag grass clippings? Basically, it is a personal preference and habit most homeowners have acquired. Another reason is that bagging does ensure that no clippings remain on the lawn to detract from lawn quality and aesthetics. Proper lawn care practices will usually eliminate surface clipping debris and ensure a successful growing season.

Rule of thumb

Frequent mowing is the key to the success — never remove more than one-third of the leaf surface at any one time.

Mow lawn grasses high and raise the cutting height slightly in the summer.

If more help is needed on this or other agricultural topics, contact David Richmond, WVU Extension agent, at 255-9321.

— Dave Richmond is the WVU Extension agent for Raleigh and Summers counties.