Crop and Soil Environmental News, April 2008
Author: Michael Goatley, Extension Turfgrass Specialist, Virginia Tech
One of the unique features of turfgrasses is that unlike most other plants in the landscape lawn grasses tolerate regular mowing at amazingly close clipping heights. Regarding mowing, there is nothing done more frequently in lawn maintenance, and also nothing done more wrong on a regular basis either! Here are some mowing tips that will improve the quality of your lawn.
Keep mower blades sharp. Mowing with a sharp blade on a standard rotary mower is one of the best ways to improve lawn quality and turf health and it also improves fuel-use efficiency and extends engine life. When is the last time the blade was sharpened and balanced? I recommend homeowners sharpen the blade at least three times per growing season: start the year off with a sharp blade, sharpen it again in late spring, and then once more in mid-late summer.
Another way to cut grass: reel mowers. An alternative to a rotary mower is the reel mower, a cutting unit that features a stationary bedknife and a spinning cylinder of blades. These mowers are making a comeback in lawn maintenance as fuel prices and environmental awareness continue to increase. I see many of these units in the lawn and garden centers of many discount stores each spring, usually in the $100 price range. These self-propelled units are certainly environmentally friendly because YOU provide the horsepower. These relatively inexpensive mowing machines work reasonably well on grasses maintained under 2 inches, but are not suitable for taller mowed turfs in the 2-3 inch range. Also, be aware that a reel mower requires specialized equipment to sharpen the cylinder of blades, a service that only specialty service stores likely provide. These mowers are ideal for relatively small, flat, and intensively maintained lawns.
Match mowing heights according to species and situation. Most mowers have adjustments for raising and lowering the mowing height. Check the cutting height settings by placing the mower on a driveway or sidewalk and measuring the height of the blade from the surface at the different settings. Then, set the cutting height to match the appropriate height of cut for your particular grass. If the lawn has a light green to white hue after cutting, it is a good bet it was mowed too low. While there are some differences in tolerable cutting heights between the various species of warm and cool-season turfgrasses, a general rule of thumb is that most grasses do well in the 2-3 inch range. For cool-season turfgrasses, frequent mowing on lower side of the recommended height is fine in the fall and early spring months, and this height actually promotes better turf density. However, by early June it is recommended to raise cutting heights prior to the summer stress period to optimize rooting depth to help the plant survive the heat and drought of summer. Many of the healthiest cool-season lawns are mowed at 4 or more inches during the summer and some are rarely mowed at all. The key to success is to not wait until summer stress arrives to raise the cutting height – it will be too late! For warm-season grasses, they prefer regular close clipping during the summer months and for these grasses, cutting heights will be raised in late summer to early fall in preparation for winter. For either type of grass, a shorter mowing height translates into more frequent mowing requirement.
What about turf in the shade? Mow on the high side of the recommended range in order to maximize the plant’s leaf area. The turf is already at a huge disadvantage to the trees in regards to light, water, and nutrients, so it needs some special attention to maintain its best canopy possible.
Follow the “1/3rd rule”. Research many years ago clearly showed that when mowing at an appropriate height for the grass, if no more than 1/3rd of the leaf blade is removed during mowing, then the grass plant will maintain a healthy balance between roots and shoots. Removing most of the foliage in a cutting event shocks the plant, forcing it to redirect its food resources from roots and stems towards new leaves. If the turf has gotten away from you, resist the temptation to scalp it in a single mowing event. Instead, slowly drop the mowing height every 2-3 days while returning the turf to its ideal cutting height range. This approach takes a little patience, but it will maintain plant health and prevent you from having unsightly piles of clippings that not only look bad, but can also shade and heat the turf below, often resulting in diseased or damaged turf.
Finally, return clippings to the turf whenever possible and if they are collected, compost them rather than placing them in the landfill. Clippings are simply organic fertilizer for the lawn and do not contribute to thatch build-up. Many rotary mowers are now outfitted with mulching attachments that chop the clippings into very fine pieces that are quickly broken down by the soil’s microbes. Almost 1/3rd of a lawn’s seasonal fertility requirement can be met by returning clippings. Treat clippings just like granular fertilizers – keep them on the lawn! Grass clippings left on the street will ultimately end up in lakes, rivers, and streams where they behave similarly to fertilizer.
Need further information? For more best management practices in lawn and landscape management contact your local Virginia Cooperative Extension office, search the VCE website (www.ext.vt.edu/ ), or log on to the VT Turf Team’s ‘Turf and Garden Tips’ blog at www.weblogs.cals.vt.edu/.
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