Tips on Warm-Season and Cool-Season Grasses
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Warm or Cool?
Nothing makes a landscape sparkle like a healthy, well-maintained lawn. Depending on where you live, you’re tending turf that contains either warm-season grasses or cool-season grasses. These different turf types require similar treatments, including mowing, aerating, fertilizing and watering. But how and when you tackle these tasks varies depending on grass type. Review basic lawn-care strategies with a regional twist, and learn how to fine-tune care for your warm-season or cool-season lawn.
Warm-season grasses, including Bahia, Bermuda, centipede, St. Augustine and zoysia spread by runners, above and/or below ground. This enables them to create a thick mat of turf that, when maintained properly, crowds out weeds with ease. The runners also mean that these warm-season grasses make great choices for erosion control. Runner-type grasses grow easily as sod, because the running stems hold the sod pieces together. With Bermuda grass, the runners spread aggressively, and you may see grass shoots appearing in flower beds and other non-lawn areas of your yard. To corral this grass, install a barrier edging that extends into soil to halt the spread of runners.
Cool-season grasses, like the fescues and ryegrass, are bunch grasses. A lawn of fescue is actually a host of individual grass plants that, as they grow, form bunches. These bunch grasses are most often sown from seed. Bunch grasses don’t naturally hold together in the form of sod, unless the sod grower uses a biodegradable net at planting time. The net holds the bunches together, enabling the grass to be harvested, rolled and installed as sod. One cool-season grass, Kentucky bluegrass, is not a bunch grass but spreads by runners.
Mowing is probably the most time consuming activity of lawn maintenance. No matter what type of grass you tend, it’s vitally important to maintain a sharp mower blade, so that you’re cutting grass blades cleanly and not tearing them, which creates openings for pests and diseases to enter. It’s also equally key to know the proper mowing height for your turf type. For warm-season grasses, turf height varies by grass type, covering a range from 1 to 4 inches. Research the type of grass you have, and maintain it at the ideal height.
Beware of Scalping
For bunch grasses, cutting grass too short can be a kiss of death. When those individual grass plants are scalped, they have to use food reserves stored in the roots to regenerate the plant. Depending on the season and the lawn’s health, recovery may not be possible. Never remove more than one third of total grass blade length at a single cutting.
Lawn Irrigation Needs
Lawn irrigation needs vary by grass type. In general, warm-season grasses need about 20 percent less water than cool-season types. Tall fescue, if it’s healthy, develops a deep root system that gives this grass type the highest drought tolerance among cool-season grasses. Bermuda, centipede, St. Augustine and zoysia warm-season grasses also develop strong, deep root systems that enable these grasses to withstand drought. Other grasses, like Kentucky bluegrass, go dormant during times of drought and revive when irrigation returns.
Fertilizer Timing: Warm Season
Fertilizer timing varies based on the type of grass you grow. In general, you want to feed a lawn just as it’s entering its peak growth. Fertilize warm-season grasses in late spring or early summer, just before grass hits its intense summer growing season. These grasses benefit from a second feeding in late summer.
Fertilizer Timing: Cool Season
Cool-season grasses kick into high gear in spring and fall. Most lawn professionals recommend one fertilizer application per year, in the fall. This feeding fuels strong root development prior to the ground freezing, enhancing the food stores in grass roots. These food stores are responsible for a strong green-up in spring. Time the fall feeding so it’s done before grass discolors when cold weather arrives. Check with your local extension office or a reputable garden center to fine-tune the timing for your area’s fall fertilizer application.
Aerating a lawn improves its health immensely by creating holes in soil that allow grass roots to receive oxygen, water and fertilizer. Aeration reduces soil compaction and ultimately enhances root growth. Just like fertilizing, you want to time aeration so it’s done just before grass enters its active growing phase. Aerate warm-season turf in late spring or early summer and cool-season lawns in early fall. Time the fall aeration so grass has four weeks of active growth before frost usually occurs.
In regions with cold winters, cut the lawn one last time before the snow starts flying. Grass will likely have stopped growing, but that’s okay. Make this mowing with your bag attachment in place. Lower the mower deck to cut grass short, maybe in the 1-inch range. This shorter height will help prevent snow mold from forming. The bag catches any debris on the lawn, such as leaves, sticks or even any lingering weed seeds. When you’re finished mowing, raise the mower deck to normal height to avoid accidentally scalping the lawn in spring.
Some cool-season turf types go dormant during summer, while warm-season zoysia enters dormancy during the year’s chilliest months. Some municipalities now require home builders to install lawns with summer-dormancy capabilities. If you choose turf that needs watering to look its best, consider adding an irrigation system before seeding, especially if soil is bare. It’s better to dig up the yard before you have grass growing. Consider what your lawn will look like in winter as you select seed. While you can remedy a winter-dormant lawn by overseeding with ryegrass, you might want to consider taking a break from lawn care.
Overseeding lawns can accomplish a variety of purposes. You might overseed a shady lawn on an annual basis to help maintain thick turf. If you have a high traffic area on your lawn, you may need to overseed that to thicken turf. Occasionally events occur that damage turf, and overseeding can repair bare spots. Overseed cool-season turf from late summer to early fall, about six weeks before the first frost. Late spring to early summer is the best time to overseed warm-season lawns.
You can lay sod from spring through fall in most of the country, and in mild winter areas, you can also install it during winter. Installing sod before your area’s rainy season is a good idea, so you can let nature help keep sod watered while rooting. Cool-season sod, if installed in early spring, can be established before summer heat arrives. If you install cool-season sod in fall, make sure it’s in place to allow at least four weeks of growth before frost arrives. You can install warm-season sod in spring, as long as you’re committed to watering when summer blazes into town.
Problem weeds vary by region, although many areas report dandelion and crabgrass as substantial weed issues in lawns. Annual bluegrass is a big problem in the South and California, purple and yellow nutsedge are prevalent in Arizona, and false dandelion is a common weed in the Pacific Northwest. Creeping Charlie or ground ivy is reportedly becoming a greater issue in many parts of the country, probably because urban forests are maturing and creating more shade. Check with your local extension office or garden center for help identifying any weeds you’re battling and for strategies to defeat these pesky plants.
Pest problems also vary greatly by region. Lawn grubs, the larval stage of a variety of beetles, such as chafer, June or Japanese beetles, are a major issue in the Northeast, Midwest, California and Arizona. Mole crickets are on turf specialists’ radar in the Southeast and Texas. European crane fly wins the pest problem award in the Pacific Northwest. Check with your local extension office or garden center for help identifying any pests you’re battling and to get strategies to eliminate or control pest populations.