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A cut above
A lush, green lawn is within your reach if you follow these tips from Clemson Cooperative Extension. Tip # 3: Stop scalping your lawn.
Photo by Mariusz Blach/istockphoto
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Calibrate your sprinkler
All you need are a few flat-bottomed containers and a ruler to measure how much water your sprinkler or sprinkler system delivers during a 15-minute test. With this calibration, you can accurately deliver the right amount of water to ensure a healthy lawn.
Photo by Jackie Jordan
You water, you weed, you fertilize, you mow, trim and edge—and still can’t seem to grow the healthy, lush lawn of your dreams. What gives? Chances are you’re making these common mistakes.
1. Watering your lawn every day or every other day
Frequent watering encourages the roots to stay close to the surface of the soil, where they are vulnerable to damage from people and pets walking on the grass. Shallow roots also make your lawn susceptible to drought stress during extended hot and dry weather patterns.
It gets worse. Frequent irrigation moves essential plant nutrients like nitrogen (which encourages the growth of grass blades) and potassium (which is essential to many plant metabolic functions) deeper into the soil column and out of the reach of grass roots. This nutrient deficiency restricts the healthy growth you want and makes your turf susceptible to disease. Frequent irrigation also creates a favorable environment for harmful insects—and the surplus insects often attract moles, which tunnel through the soil, literally undermining all your hard work.
Most residential lawns respond best to deep and infrequent irrigation. Warm-season turf grasses like Bermuda and zoysia have the best drought tolerance, while centipede and St. Augustine have moderate drought tolerance. Tall fescue is the most commonly grown cool-season grass in South Carolina and usually requires irrigation to remain attractive during the summer months.
A good universal recommendation for both warm-season and cool-season grasses is to apply one inch of water a week. For heavy clay soils, apply the inch in a single application. For lighter soils, it is best to apply a half-inch two times a week. This application should soak the root zone to a depth of 8 to 10 inches and allow the grass to dry before the next watering session.
For an accurate measure of your sprinkler’s output, gather several straight-edge containers of the same size—cat food cans and tuna fish cans are ideal; plastic food storage containers will work if they aren’t bowl-shaped. Place the containers in various spots of the irrigation zone. Turn on the sprinkler system and allow it to run for 15 minutes. Use a ruler to measure the depth of water collected by each container. Now you know how much time to let the system run to achieve the recommended irrigation level. If you have an automatic sprinkler system, be sure to conduct this test in each zone.
During hot and dry weather, supplemental irrigation may be needed. It’s time to water again when the lawn takes on a bluish cast or the blades fold up. Walk across your lawn in the evening. If the grass in the footprints remains flat, plan on watering your lawn the following morning.
2. Watering your lawn in the afternoon or early evening
Irrigating your lawn in the afternoon or early evening does a disservice to you and your grass. The best management practice is to water before dawn.
When irrigation is applied during the afternoon, as much as 20 to 30 percent of the water can be lost to evaporation. Even in the best of conditions, only about 2 percent of the water that does make it to the plant roots fuels the photosynthesis that creates lush, green growth. The other 98 percent passes through the plant in a process called transpiration.
The time between 10 a.m. and 4 p.m. tends to be the hardest on plants. This is when the temperature and sun exposure are at their greatest. If you wait until the afternoon to deliver water, the grass goes most of the day unable to make its own food.
Routinely watering in the early evening has a different drawback: It doesn’t allow sufficient time for the blades to dry off before dew falls and a humid microclimate is created around the blades. This favors the development of diseases like gray leaf spot, rust and the curvularia fungus.
The best management practice is to water pre-dawn. If irrigation is applied between 2 a.m. and 9 a.m., the leaves have the entire day to dry, and the lawn and other plants in the landscape can efficiently photosynthesize throughout the day.
3. Scalping the lawn
Routine mowing is an important maintenance practice in developing a thick, lush lawn, but if your turfgrass resembles a drill instructor’s crew cut, you’ve taken a good thing too far.
Set your mower depth so that you’re never removing more than one third of the grass blade. Cutting deeper causes the grass to divert energy from developing strong, healthy roots and promotes the growth of stems. Water and nitrogen consumption increase as a result, but the density of the grass is reduced. Routinely scalping the lawn can also cause the grass to go into dormancy sooner and your lawn will suffer more heat stress and cold damage as a result.
Proper mowing height and frequency ensures clippings will quickly break down and feed the soil. Contrary to popular belief, clippings do not contribute to thatch. Clippings are 30 percent nitrogen, and reincorporating them into the soil can dramatically reduce fertilizer requirements.
Each turfgrass has a recommended height range for mowing. Keep the grass cut at the lower end of the range early in the season to help thicken up the lawn. As the weather heats up, raise the mowing height to help grass handle the additional stress. To help warm-season grasses like centipede and St. Augustine overcome winter temperatures, keep the mowing height raised to the highest recommended cut as the grass begins to go dormant in the fall.
Recommended mowing heights
- Bermuda grass—1 to 2 inches
- Hybrid Bermuda grass—.5 to 1.5 inches
- Centipede—1.2 to 2 inches
- St. Augustine—2.5 to 4 inches
- Zoysia—1 to 2 inches
- Tall fescue—3 to 3.5 inches (summer); 2 to 3 inches (winter)
4. Mowing with a dull blade
It is important to use a sharpened blade when mowing. Dull blades result in ragged cuts that give the grass a whitish cast, stunt growth and make your turf susceptible to disease. Sharpen or replace your mower blades at least once a year.
5. Applying fertilizer incorrectly
Each species of turfgrass has unique nutritional needs. Centipede grass has a very low nitrogen requirement compared to other lawn grasses. It only requires 1 pound of nitrogen per 1,000 square feet per year. Bermuda has a higher fertilizer requirement and requires 3 to 4 pounds of nitrogen per 1,000 square feet per year. To figure out your square footage, multiply the width of your property by the length of your property and subtract the square footage of the house, driveway and flower beds.
For a more precise picture of your landscape’s fertilizer needs, it never hurts to have your soil tested. See: “Digging up answers with soil samples."
When you fertilize is just as important as what type of fertilizer you use. Warm-season grasses should not be fertilized until they have completely greened up in the spring. A good rule of thumb is to wait until after the beginning of May, but to stop all fertilization after the early part of August. Cool-season grasses are just the opposite. They should be fertilized in September and again in early March.
Look for fertilizer that contains one-third of its nitrogen in a slow-release form. This will give a slow, steady feeding of nutrients over the course of six weeks. And never use more than the recommended amount. Measure the fertilizer before it goes into the spreader using this handy rule of thumb: Two cups of fertilizer equals approximately one pound.
Apply fertilizer to dry grass blades and then water it. To ensure an even application of fertilizer, split the recommended amount in half. Apply the first half back and forth in one direction, then rotate 90 degrees and apply the remaining fertilizer. If you are unsure of what setting to use on your spreader, set it to the lowest setting. Keep applying the fertilizer in alternating patterns until you have applied the recommended amount to the lawn.
For more information on lawn care, consult the resources at the Clemson Cooperative Extension Home & Garden Information Center at hgic.clemson.edu/category/lawns/ or contact your local extension office.
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Jackie Jordan is a Clemson University Cooperative Extension agent and Master Gardener coordinator for Fairfield, Kershaw and Richland Counties.
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