Managing Mowing For Top Quality Turf

During the rush of the season, as grass seems to grow more rapidly than Jack’s Beanstalk, it’s easy to focus completely on covering ground quickly with mowers. Yet grass is a complex organism and squeezing in a few extra minutes to ensure that proper mowing procedures are followed will pay off in the future. Managed mowing results in a more vigorous plant with greater stress resistance.

Mowing decisions concerning cutting height, frequency and patterns impact far more than aesthetic appeal; they affect turf health, density and grass variety dominance.

THE NATURE OF GRASS. Mowing is an option in turf control because of the nature of grass. The plant’s growing points are located immediately above the nodes, in the leaf at the base of the sheaths and at the base of a blade. Grass vegetative growth consists mostly of leaves, with little elongation of stems. The stems and growing points (buds) are concentrated near ground level. Because of this, mowers can cut away the tips of the grass leaves without stopping their growth or the formation of new leaves.

Mowing does alter natural conditions. The plant needs the grass leaf area (the blade) for food production and other plant life processes. Each pass of the mower blade inflicts a wound on the grass blade. The plant compensates for this attack by channeling more food (carbohydrates) to leaf growth and by “feeding” the roots, rhizomes and stolons. Since the plant attempts to balance its above-ground growth with its below-ground growth, this may slow or stop root development until leaf growth is restored.

Different grass types, and cultivars within those types, have varying tolerance levels to mowing. Creeping, stolon-producing grasses, such as bermudagrass, tolerate close mowing. More upright grasses, such as bluegrass and ryegrass, require higher mowing levels to function properly. Most fine-bladed grasses tolerate lower mowing heights than coarse-textured grasses.

The best height of cut is determined by the natural growth pattern of the specific grass variety (physiological characteristics); the form and structure of the specific grass cultivar (morphological characteristics); the physical characteristics of the site; the vigor and density of the turf; and the environmental conditions.

For cool-season grass growth, the ideal temperature range is 60 to 75 F; for warm-season grasses, the range is 80 to 95 F. Temperatures above or below these ranges put the turf in a period of dormancy.

Grass blades insulate the growth points against heat or cold. The leaf tissue also serves as a shield, protecting growth points from mechanical injury caused by traffic and wear.

Research has proven that mowing near the top range of height of cut for each grass variety allows the plant to develop deeper roots and greater root mass, more mass for photosynthesis and more tillers for density. Too low a cut puts the turf under stress, forces it to deplete vital food reserves and makes it more susceptible to disease and insect invasion.

In addition, mowing patterns combine with height of cut to keep grass growing straight up and increase turf vigor. Ideally, crews should alternate mowing directions each time the turf is cut. Mowing strategies, however, are highly individualized according to the property’s turf and maintenance requirements, as well as local growing conditions.

COOL-SEASON LINEUP. The cool-season grasses include bluegrass, perennial rye-grass, fine-leaved fescues and turf-type tall fescue. All have a suggested cutting range of 2 to 3 inches.

New cultivars of perennial ryegrass take abuse better. Bluegrass has better recuperative qualities, extending turf life. Newer turf-type tall fescues withstand summer heat and low levels of moisture better, and fine-leaf fescues tolerate shade. Experiment to find the specific combination of cultivars that prove most adaptive to your clients’ individual lawn conditions and regional environmental factors.

During drought conditions, raising mowing heights to 2½ inches or even higher can reduce water use and provide better cooling for the grass roots. During extremely wet seasons, mowing heights could be lowered to 2 inches or even 17/8 inches to increase soil level evaporation.

“WIRY” WARM-SEASON TURF. Most hybrid bermudagrasses in southern regions can take close mowing, with some tolerating a suggested height of cut ranging as low as ¼-inch. But that range is generally reserved for specialized turf, such as the reel mower manicured turf of athletic fields. When rotary mowers are used, the height of cut for hybrid and common bermuda-grass generally ranges from 1 inch to 1½ inches. Zoysiagrass usually performs well at the 1-inch to 2-inch range.

With all rotary mower cutting situations, the height of cut must be compatible with the mower deck size in relation to the site terrain. High spots, low spots, bumps or indentations can affect the angle of the mower deck and thus the position of the cutting blades in relation to the grass blades.

The “wiry” nature of many creeping warm-season grasses makes mowing height especially critical. These grasses produce so much top growth they will “puff” and “pile” up if allowed to get too long. This, followed by mowing at too low a cutting height, removes so much leaf tissue the “wiry” stems are exposed and turf vigor suffers. Change height of cut gradually to avoid shocking the plant.

CROWDED TRANSITION ZONE. The transition zone is too cool for warm-season grasses and too warm for cool-season grasses. Contractors often work with both types to maintain a decent, usable turf cover.

Where winter temperature ranges allow adequate survival rates, a warm-season bermudagrass may be used as a base for its strong root structure. This base can then be overseeded with a blend of cool-season perennial ryegrasses to give late season color.

A bermudagrass mowing height of 1 inch or more is generally best during the hot months when this grass is dominant.

Mowing height should be dropped to the scalping level for one mowing prior to overseeding with perennial ryegrass for better seed-to-soil contact. As this cool-season grass becomes dominant, height of cut moves to the 2- to 2½-inch range.

As temperatures warm in the spring, gradually returning mowing heights to the previous optimum levels for bermudagrass is recommended to discourage the perennial ryegrasses and to allow the bermudagrass to regain dominance.

When bluegrasses and fine-leaf fescues are used year-round in the transition zone, it may be necessary to resort to mowing heights of 3 inches and higher during high temperature periods to provide cooling.

MOWING FOR QUALITY. Match the height of cut to the natural growth patterns of the grasses, the weather and property use. Start by preparing crews for seasonal changes in mowing practices. Adjust the height of cut and mowing frequency gradually. Never remove more than one-third of the grass blade with any one mowing.

This may mean adjusting the mowing height several times a day to meet the specific turf needs on different properties. Grass on a residential property with an in-ground sprinkler system and a fertilization program will grow at a significantly different rate than that of the outlying areas of a commercial site, even if they are the same varieties.

As growing conditions gradually change from wet to dry and the “lushness” of the grass declines, be aware that the ground speed of mowing equipment will increase. The ground speed of walk-behind mowers is limited to the walking speed of the operator and generally remains at an acceptable level. With riding mowers, the ground speed is limited only by the capabilities of the machine.

Less experienced operators may push riding mowers to top speed, affecting safety and cut quality. Faster speeds make it more difficult to spot debris and on uneven terrain or hillsides it can affect machine stability. It may be necessary to set speed limits for certain units or specific areas.

Mowing too fast can reduce the quality of cut, no matter what the mowing height. With thick grasses, the equipment engine may signal excessive stress by developing engine lug. Heavy grass can plug the mowing unit, forcing the operator to make frequent stops to clear the discharge area. With slower growing summer grasses, the mowed area may appear uneven or ragged.

SMOOTH CUTS. Turning corners too fast is detrimental on wet or dry turf. Operators should slow down enough on turns to keep the inside tire from spinning or tearing up turf. Wheels slip and spin on wet grasses, which in turn ooze more slippery juices. When the grass is flattened in spots, height of cut can’t be consistent. This increases compaction, and skidding wheels may damage the crowns of the grass plants. With dry conditions, the turf is more fragile and the rooting is less secure. Fast turns can break, rather than cut, the grass blades or even uproot the entire plant.

When grass is lush, it’s easier to spot deficiencies in the quality of cut. But when grass grows slowly, it’s harder to tell when quality falls. Remind operators to observe their mowing, especially with wider mowers and multiple deck systems. Big bumps or hill shock load could even shut off one of the decks. Check the appearance of each swath immediately after it’s mowed to prevent a poor quality cut across an entire lawn.

SMART MANAGEMENT IDEAS. Smaller mower decks generally deliver a higher quality of cut, so mow high-profile areas with the smallest practical deck size. In less heavily used areas where aesthetics aren’t as critical, use larger size mower decks. It’s best to schedule the mowing of difficult and high profile areas early in the day when operators are fresher and their efficiency levels are highest.

Check the rotary mower deck height adjustment from side to side and front to rear. Improper adjustment from side to side produces uneven grass blade lengths across the cutting swath, while improper adjustment from front to back generally puts an unsharpened portion of the mower blade in contact with the grass. This will beat or tear the grass blade, rather than cut it, and produce extra drag on the machine.

The rapidly turning blades of rotary mowers create air movement within the housing of the deck that keeps grass blades standing upright in the best position for the mower blades to clip them. Clean rotary mower decks frequently to insure proper air movement. This also will allow free circulation of the clippings within the deck and more efficient clipping dispersal.

Mower blades should be kept sharp in hot weather as in the rapid-growing spring season to keep turf healthy and attractive.

Keep a backup set of blades sharpened for each mowing unit. Technicians can sharpen blades that are removed as time permits so they are ready for the next exchange.

Mowing is more complex than merely moving a machine over the turf. Allocating those few extra minutes to match the procedure to grass needs will produce better results and more satisfied clients.

The author is product manager — market development, commercial mowing for John Deere in Horicon, Wis.