WHAT IS THE BEST WAY TO MOW MY GRASS?
, 5 min reading time
First of all, mowing is a very destructive process as far as the plant is concerned. When mowing, we constantly defoliate the plant, which causes serious damage. So, why are the grasses that we use as turfgrasses able to tolerate this abuse. Part of the answer lies in the way grasses are structured. All grasses have what we call subapical meristems. The meristem is the part of the grass where new cell division and growth first take place. In most plants, the meristem is found at the tip of the stems. If the plant is defoliated, the meristem is removed and new growth is not possible. Grass meristems are at the base of the leaf and stems and when the structure is defoliated the growing point remains and growth can continue. However, not all grasses can be maintained as a turf. Most of them will die if they are defoliated. In fact, of the 10,000 grasses on earth, only about 50 species are useful for maintaining a turf stand. The turfgrasses are generally very small, compact plants that grow close to the ground. Plants like bamboo and corn are grasses, but they grow several feet high and could never be mowed. There are many compact grasses, though, that cannot be maintained as turf and there is more to it than just compactness.
Grasses are green plants. The green color comes from chlorophyll, the material that allows plants in the presence of sunlight to produce their own food supply through the process of photosynthesis. The food materials produced by photosynthesis are called carbohydrates. Mowing removes photosynthetic tissue and starves the plant. The turfgrasses are special in that they can compensate for this loss of tissue above the mowing height by increasing the density of the grass stand below the mowing height. By doing this, they can survive continuous defoliation and form a dense, attractive stand of grass that we call turf.
Among the turfgrasses, there are differences in how low you can mow them on a continuous basis. It is generally the stoloniferous grasses that can be maintained at the lowest heights. Stolons are above ground stems that hug the surface of the ground and allow the plant to continue producing carbohydrates through photosynthesis even at very low mowing heights. More upright growing grasses like Kentucky bluegrass and tall fescue lack stolons and must be maintained at a higher mowing height. Table 1 contains standard mowing heights for many of the common turf species.
Table 1. Mowing heights for common turf species.
|
GRASS |
MOWING HEIGHT IN INCHES |
|
KENTUCKY BLUEGRASS |
1.5 - 3 |
|
PERENNIAL RYEGRASS |
1.5 - 3 |
|
TALL FESCUE |
2 - 3.5 |
|
FINE FESCUES |
0.5 - 2 |
|
CREEPING BENTGRASS |
0.08 – 0.8 |
|
BERMUDAGRASS |
0.25 – 1.5 |
|
ZOYSIAGRASS |
0.5 - 2 |
|
BUFFALOGRASS |
1 to UNMOWED |
Even for the best suited grasses, mowing is still a stress and their ability to adapt to low mowing heights is limited. For all turfgrasses, as the mowing height is reduced, the reduction in carbohydrates also limits the amount of root growth underground (Figure 1). Raising the mowing height is a good way of reducing stress on even the best adapted grasses.
Not more than 30 to 40% of the grass should be removed in any single mowing. If you plan to maintain the grass at a 2 in. mowing height, let it get up to 3 in. and then cut it back to 2 in. Removing more than 40% of the tissue in any single mowing can result in a condition known as scalping which damages the grass. It can take weeks to recover from scalping. If the grass has been allowed to grow to an excessive height, follow the 30 to 40% but mow more often until the grass has had a chance to adjust to the lower height.
The lower the mowing height, the more often you will need to mow. Creeping bentgrass on a golf course green mowed at a 0.1 in. height will require daily mowing, whereas Kentucky bluegrass maintained from 2 to 3 in. can be mowed weekly.
Grass is generally mown with either a reel or a rotary mower (Figure 4). Reel mowers are best for low mowing heights like those used on golf courses. Reel mowers are expensive and cost a lot to maintain. They are generally used on professional areas like golf courses and sports fields. Rotary mowers are generally satisfactory for the higher mowing heights used on lawns.
Be sure to use a sharp mower. Dull mowers can shred the tissue and cause a problem that appears similar to a disease (Figure 3). This is a common problem on home lawns. The mower should be sharpened at least once per year.
Figure 1. The effect of mowing height on density above ground and rooting underground.
(Drawing by J.M. Lenahan, from Fundamentals of Turfgrass Management 4th ed.)
Figure 2. (Drawing by J.M. Lenahan, from Fundamentals of Turfgrass Management 4th ed.)
Figure 3. Use sharp mowers when cutting grass.
Figure 4. Reel and rotary mowers used for maintaining turf.
(Drawing by J.M. Lenahan, from Fundamentals of Turfgrass Management 4th ed.)
Nick Christians, University Professor of Horticulture, Emeritus, Iowa State University
books: http://www.amazon.com/Nick-Edward-Christians/e/B001H6SB7A/ref=ntt_dp_epwbk_0
turf blog: http://www.iaturf.blogspot.com/
Fundamentals of Turfgrass Mgt. 5th ed http://www.wiley.com/WileyCDA/WileyTitle/productCd-1119204631.html
Web site: https://www.hort.iastate.edu/directory/nick-christians/