Spring Planting Considerations for Warm-season Turfgrasses in Virginia Lawns
This information will assist you in proper warm-season turfgrass selection, seedbed preparation, seeding method, as well as provide other lawn establishment tips pertaining to fertilization, irrigation, mowing, and weed control.
Lots of grass seed is being planted across the state of Virginia this spring, much of it out of necessity following a very difficult growing season last year. However, it is important to note that there are major differences in the likelihood of success depending on several factors, including the selection of the proper turfgrass for your site and location. Use the following information to assist you in proper warm-season turfgrass selection, seedbed preparation, seeding method, and other establishment tips pertaining to fertilization, irrigation, mowing, and weed control.
What type of warm-season grass are you considering? Bermudagrass and zoysiagrass are adapted in both the Piedmont and Tidewater regions, and in addition to these grasses St. Augustinegrass and centipedegrass can both be managed along the coast. In the Ridge and Valley, zoysiagrass receives some limited use because of its outstanding cold tolerance. For all of these grasses mid-spring through mid-summer is an ideal time to plant.
Unfortunately, seed is not available for all cultivars. The “Recommended Turfgrass Varieties” publication linked on this webpage lists vegetative-only (i.e., grasses that can only be sodded, plugged or sprigged) and seeded cultivars for both bermudagrass and zoysiagrass. All of the warm-season grasses can be established vegetatively, but seed are available for some. Seeded bermudagrass and zoysiagrass should be planted at rates of 0.5 to 1 pound and 2 to 3 pounds per 1000 sq ft, respectively. Centipedegrass can be planted at as little as 0.25 to 0.5 lbs per 1000 sq ft. St. Augustinegrass is almost always established vegetatively by sod or plugs. Be aware that the large retail garden centers might not carry Virginia Tech’s recommended varieties, so you might have to purchase or order these grasses from a specialty garden center or turf supply store. Sod or plugs might be available at retail nurseries, but be sure to also consult Virginia’s Sod Directory (linked in this blog) in case you are interested in purchasing vegetative material directly from the grower. More information on these grasses and their establishment and maintenance programs is available in the VCE publication “Spring and Summer Lawn Management Considerations for Warm-Season Turfgrasses”.
Soil preparation. It’s wise to conduct a soil test with which to make any adjustments in soil fertility or pH prior to planting. Consult your local county extension office for instructions and sampling boxes needed to collect and submit your sample. A Macromedia Breeze presentation entitled “Soil Testing for the Lawn and Landscape” can be accessed with this podcast. Phosphorus is the nutrient typically deemed most critical for plant establishment, and it is commonly emphasized in “starter” fertilizers (i.e., fertilizer grades such as 5-15-10). However, there is little to gain by applying more phosphorus if the nutrient is not limiting in the soil. Excessive soil phosphorus may contribute to surface water quality impairment when it is not managed appropriately, so be sure to apply phosphorus only when recommended by a soil test. Ideally, preplant incorporate no more than 1 pound of nitrogen per 1000 sq ft into the soil. Incorporate all fertilizer and lime into the prepared bed prior to planting.
Some level of soil preparation is necessary to maximize turf establishment whether the grass is planted by either seed or sod. For seed establishments, soil tillage to a depth of 3-4 inches is the preferred method for seedbed preparation in complete renovations. Do not till the soil so aggressively that you remove all clods; some tillage is good, but it is not necessary to convert your soil to powder! If you are only trying to thicken an existing stand of grass, then consider using a vertical mower (i.e., de-thatcher) or a coring machine (i.e., an “aerifier” or “plugger”) on the soil prior to seeding. Remember anything that you can do to promote soil to seed contact enhances establishment. Even sodded or plugged grasses (bermuda, zoysia, centipede, or St. Augustinegrass) should be established in a tilled planting bed whenever possible.
Planting tips. All seed for warm-season grasses are very small and are applied in small amounts as previously detailed. You will likely need to “dilute” the seed with a dry carrier such as an organic fertilizer or sand to accurately spread the seed over a large area at the recommended planting rate.
Apply seed in multiple directions to minimize the likelihood of skips. After seed application, lightly drag or rake the seed into the soil surface in order to maximize soil to seed contact. Be careful not to bury these small seed or else they might never emerge from the soil. To further enhance the chances of establishment success, apply a mulch after planting in order to conserve moisture. One of the best and most affordable mulches is weed-free wheat straw. This mulch can be applied at up to one bale per 1000 sq ft. Wheat straw mulch applied at this rate will not have to be removed after planting but can simply be mulched with your mower the first few times the turf is clipped.
What are some tips to properly install sod? First, begin sod installation along the longest, straightest line available (e.g., a sidewalk or driveway) and stagger the seams. Butt seams together, but be sure not to stretch or tear the sod excessively when fitting together. The final step should be to roll the sod to ensure sod to soil contact and minimize desiccation.
For plugging establishment, a somewhat unique method of planting possible with all warm-season grasses because of their creeping growth habit, it is ideal to use at least 4- inch diameter plugs to accelerate grow-in. Bermudagrass and St. Augustinegrass can typically achieve 100% coverage within 6 to 8 weeks if these sized plugs are planted on 12-inch centers under a regular nitrogen and irrigation program. Centipedegrass plugs will usually attain full cover within 8 to 12 weeks. Understand that zoysiagrass plugs might not completely cover until the second growing season. If using commercially available 1-inch diameter zoysiagrass plugs, plant them at no more than a 6-inch spacing and anticipate that you will likely have full coverage within 12 months. The slow establishment rate of zoysia is troublesome, but if you are patient you will be rewarded with one of the highest quality, most dense, slowest growing turfgrass canopies possible.
An additional planting method used mostly in some bermudagrass lawn establishments is sprigging, the process of planting the stems from shredded sod into the ground. This method requires much more attention to initial watering during establishment and there is a high likelihood of turf desiccation. Therefore, while it is an important means of establishing golf and sports turf, it is not a common lawn establishment method for warm-season grasses.
Additional fertilization after spring establishments? Realistically, any additional fertilization should not be made until after the development of an extensive root system. For seeded, plugged, or sprigged grasses, initiate regular N fertilization after lateral stems (stolons) are visibly creeping across the surface. For sod, ensure that the turf has firmly rooted to the ground before supplying additional fertilizer for summer maintenance growth.
Irrigation. For seed establishments, irrigate lightly and frequently on a regular basis until germination is complete. You neither want to drown nor wash away your seed. Slowly decrease the frequency of watering as establishment proceeds until your maintenance irrigation program becomes a “deep and infrequent” watering schedule that promotes the deepest root system possible. Sod and plug establishments obviously will accept more initial watering on a less frequent basis. Again, do not saturate the rootzone because this discourages rooting. Keep newly installed sod and plugs moist, and reduce irrigation amounts as previously described as rooting proceeds.
Mowing. Keep it simple and mow the grass when appropriate in order to keep the “one-third leaf rule” in effect (i.e., never remove more than 1/3 of the leaf blade at any mowing event). Use the recommended mowing heights detailed in our other VCE publications and remember that it is absolutely essential to mow with a sharp blade during the first few cuttings in order to reduce seedling mortality. Another important tip is to ensure the soil is sufficiently dry for mowing so that you do not rut your new lawn with wheel tracks or footprints. Finally, understand that frequent mowing of warm-season grasses in their first season of development is critical in maximizing turf density.
Weed control. Overall, one should anticipate quite a bit of weed pressure from any spring planting, but there are major limitations in annual grass control from chemicals during spring seedings. For instance, almost all preemergent herbicides used for crabgrass control are not labeled for controlling weeds during the seeding of warm-season grasses. There are a few herbicides available for treatment by licensed lawn care managers for seeded warm-season grasses, but these options are quite limited and often very expensive. There are several preemergent herbicides labeled for use in either sod, plug, or sprig plantings, but these too must be used with caution. What about postemergent weed control as the turf matures? Numerous postemergent grass and broadleaf herbicides can be used on newly established turfgrasses AFTER the turf has been mowed at least two times or after stems are visibly creeping along the soil surface. Consult and follow the labels for all chemicals very carefully before making any of these treatments.
Summary. Mid-spring through mid-summer is the preferred time for warm-season turfgrass establishment. By following these tips, you should be able to successfully establish a great looking lawn that you will enjoy for many years.
Are you interested in further information? Links to Virginia Cooperative Extension publications that specifically pertain to spring lawn establishment have been provided in this podcast and in the attached transcript. There are many publications full of valuable information on a host of topics that can be found at the Virginia Cooperative Extension webpage at www.ext.vt.edu. This site contains links to all VCE publications and contact information specific to your locale. Please contact your local Virginia Cooperative Extension office if you require further assistance.