Mowing is a basic lawn care task, but it might surprise you to know it’s not always done properly. To support and increase the overall health of your turfgrass, it’s important to follow essential mowing practices.
The best defense against weeds, disease, and pests in a lawn is deep roots. Root depth depends on sufficient blade length — the taller the grass blades, the deeper the roots, and the shorter the blades, the shallower the roots. Grass also needs a certain blade length for photosynthesis to produce the carbohydrates it needs to survive.
That’s why all grasses have a lowest optimum mowing height, which varies with grass type and even its cultivars (varieties of a specific plant created from a natural species and maintained by cultivation). If you always mow below the recommended mowing height, photosynthesis is restricted. The grass must then use its stored energy to replace the blades to attain optimum photosynthesis. Until that occurs, the grass is in a weakened state, and can’t put energy into growing deep roots.
Each grass type and cultivar also has a highest optimum mowing height. Grass left too tall has an increased risk of disease and pests, such as ticks, fire ants, fleas, and rodents. On the other hand, blades at the tallest recommended height for their type retain more moisture and shade the soil better.
Recommended Mowing Heights
Common warm season turfgrasses in Central Texas include: St. Augustine, Bermuda (common or hybrid), zoysia (coarse or fine), and buffalo. Here are low and high optimum mowing heights for these common turfgrasses for home lawns as recommended by Texas A&M AgriLife Extension:
- St. Augustine — 2.5 to 4 inches
- Bermuda (common) — 1.5 to 3 inches
- Bermuda (hybrid) — 1 to 2.5 inches
- Zoysia (coarse) — 1 to 2.5 inches
- Zoysia (fine) — 1 to 2 inches
- Buffalo — 2.5 inches to 4 inches. Can leave unmowed in natural areas
Generally, turfgrass should be maintained at the optimum height for its type and cultivar. This is especially true for turfgrass in shaded areas, as more leaf surface is needed for photosynthesis.
Mowing frequency will vary greatly, depending on grass type, rainfall, fertilization applications, and time of year. Mow often enough that you’re not removing more than 1/3 of the leaf blade height at each mowing — this avoids stressing the grass. For example, if you want the mowing height (height after the lawn is mowed) to be 2 inches, then mow before the lawn grows past 3 inches.
To follow the 1/3 rule, turfgrasses that are kept at a lower height will need more frequent mowing. See chart below.
From: Mowing Your Lawn by Matthew Bertucci and John Boyd,
University of Arkansas, FSA6023-PD-11-18RV
The 1/3 rule also prevents weed germination. If your mowing height is too low for your grass type, weeds such as annual bluegrass, crabgrass, and dandelion have a chance to grow.
During peak growth periods (late spring, early summer) more frequent mowing may be needed for warm-season grasses (e.g., two times a week) to prevent “scalping” the lawn. Scalping is excessive removal of grass height, leaving only the stem. Not only will this ruin the beauty of your lawn, but it also decreases its health. You can avoid the likelihood of scalping by:
- Mowing regularly at higher mowing heights
- Reducing the mowing height gradually over several mowings for overgrown grass
- Using a reel mower for lower heights
- Alternating the mowing pattern for each mowing to encourage upright shoot growth (e.g., at right angles) and to minimize grain (horizontal growth orientation)
Grass clippings are a valuable source of nutrients and can reduce the need for nitrogen fertilizers by up to half. Make sure the clippings are dispersed evenly across the lawn and let them settle naturally onto the soil where they’ll decompose. Returned grass clippings usually don’t contribute to thatch formation when you mow regularly, as the clippings are small and are broken down easily.
If longer clippings or piles have accumulated on top of the grass, spread them across the lawn using a rake. This prevents blockage of sunlight and water to the underlying turf.
There are situations in which you might want to remove or bag clippings:
- During the reproductive growth stage of weeds when flowers, seed heads or other reproductive plant tissues such as rhizomes and stolons are present.
- When mowing areas affected with disease or insects. Also, clean mower blades before moving to unaffected sections.
- When the grass is wet, causing clippings to clump together and not spread evenly.
Use a lawnmower with adjustable heights that are easy to identify. Reel, rotary, and mulching mowers are all suitable for St. Augustine, Bermuda, zoysia, and buffalo grasses.
Reel mowers give a more precise cut and are ideal for grass with a lower mowing height. With rotary mowers, the cut isn’t as precise, and can be damaging to the leaf blade. However, it’s easier to change the mowing height with a rotary mower. Mulching mowers do a better job of cutting the grass clippings into small, fine pieces, allowing them to fall down to the soil easily and decompose more quickly.
Make sure the mower blades are always sharp. Dull blades tear the leaf blades instead of cutting them, giving the lawn a ragged, brownish look, and causing injury. Injured grass is more vulnerable to disease, insects, and environmental stresses such as heat and drought.
Start mowing in the spring after the grass has greened up and continue recommended mowing practices until your warm-season grass goes dormant in the fall after the first frost. You only need to mow your dormant lawn if winter annual and perennial weeds are growing. Bagging the clippings that contain weed seed heads, stolons, and rhizomes will help to prevent the weeds from spreading.
When Not to Mow
Avoid mowing when the grass is wet. Wet clippings bunch up on the lawn rather than dispersing and can also clog the mower. It’s easier as well for disease organisms to spread in wet grass, and newly cut leaf blades provide ready entry points. When the grass is extremely wet, mowing can create wheel ruts, and there’s also the risk of tearing up the turf.
Don’t mow the lawn during the hottest time of the day in the summer, or during drought periods. The lawn is already under stress, and foot traffic and cutting will only make the situation worse.
Sound irrigation practices are indispensable to a healthy and vibrant lawn. Call the licensed irrigators at Smart Earth Sprinklers at (512) 694-1147 or contact us online to keep your sprinkler system operating at its best.