Spring Planting Considerations for Cool-season Turfgrasses in Virginia Lawns

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 cool-season turf selection, seedbed preparation, seeding method, and other establishment tips pertaining to fertilization, irrigation, mowing, and weed control.

What type of cool-season grass are you considering? Lots of cool-season turfgrasses (fescues, ryegrasses and bluegrasses) will be planted from seed in Virginia lawns this April and May and it is important to understand the challenges you face with these grasses in spring plantings. First, it is always preferred to plant these grasses in late summer to early fall in order to optimize grass establishment and maturity before the onset of summer. The primary factor in turf establishment success is the development of an intensive, healthy root system, and this is difficult if not impossible to achieve with a spring planting. However, if you are faced with either a sparse turf or the need to plant a new lawn this spring, you have no other choice but to do the best you can.

Choosing the appropriate grass is the first step, and briefly put, the only two cool-season grasses that have application in the Piedmont and Tidewater regions of the state are tall fescue and the new hybrid bluegrasses. Initial research trials evaluating these bluegrasses have been installed at Virginia Tech’s research locations in Blacksburg and Hampton Roads. To date, the hybrid bluegrasses in Dr. Jeff Derr’s trials at Hampton Roads look particularly promising for our state’s hotter, drier climates. In the Valley and Ridge regions, these grasses and others such as fine-leaf fescues, Kentucky bluegrass, and perennial ryegrass can be grown in lawns. The VCE publications “Establishing Lawns” and “Spring and Summer Lawn Management Considerations for Cool-Season Turfgrasses” (these can be found at the VT Turf link on this webpage) give the recommended seeding rates for most of these grasses. Where rates are not provided (for example, the new hybrid bluegrasses), follow the recommendations on the seed bag. Use the highest recommended seed rates for spring establishments because the warmer temperatures of the spring and summer greatly increase seedling mortality.

Seed are readily available for many cultivars of cool-season grass species. Consult the “Recommended Turfgrass Varieties” link provided here or under VT Turf to select the best performing cultivars in Virginia according to Virginia Tech’s field trials. Be aware that the large retail garden centers might not have these varieties available, so you might have to purchase or order these grasses from a specialty garden center or turf supply store.

Soil preparation. The first step in soil preparation is a current 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 through the Virginia Tech Turf link. 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, which will reduce the benefits of good soil structure. 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. Anything that you can do to promote soil to seed contact enhances establishment. Even sod should be established in a tilled planting bed.

Planting tips. Kentucky bluegrass seed are extremely small and it is logical that small seed go out in small quantities. You will likely need to “dilute” the seed with a dry carrier, possibly some form of amendment such as an organic fertilizer or sand to spread the seed at the recommended planting rate. Larger seeded grasses such as fescue and ryegrasses do not require mixing with a carrier to accurately deliver the desired 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. Be careful to not plant the seed too deeply if using a drill seeder (an effective tool for optimizing soil to seed contact). Small seed need to be very near or on the soil surface to successfully establish. To further improve establishment success, apply a mulch after planting to help conserve moisture. One of the best and most affordable mulches if it is weed-free is wheat straw. This mulch should be applied at no more than one bale per 1000 sq ft. Wheat straw mulch applied at this level will not have to be removed after planting but can simply be mulched with your mower the first few times the turf is cut.

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.

Additional fertilization after spring establishments? Realistically, any additional fertilization should not be made until after the development of an extensive root system. For cool-season grasses, it is anticipated that the pre-plant fertilization should be adequate for spring establishments. Additional N will only further weaken the root system and increase environmental and pest pressure. For sod installations, ensure that the turf has firmly rooted to the ground before applying additional fertilizer.

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 that promotes the deepest root system possible.

Sod 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 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. It is absolutely essential to mow with a sharp blade for the first few mowing events to reduce seedling mortality. Ensure the soil is sufficiently dry to mow so that you do not rut with your wheel tracks or footprints. It is fine to mow on the “taller” side for cool-season grasses to promote first summer survival.

How about weed control for a new planting? Anticipate quite a bit of weed pressure from any spring planting, but especially with cool-season turfgrass establishment. There are major limitations in annual grass control from chemicals during spring seedings. For instance, most pre-emergent herbicides used for crabgrass control are not suitable for controlling weeds during the seeding of warm or cool-season grasses. One preemergent herbicide popular for spring seedings of cool-season turfgrasses that is available to homeowners is a product that contains the active ingredient siduron. It is commonly marketed on store shelves as a “starter” herbicide and the active ingredient is often carried on a starter fertilizer. This product controls germinating crabgrass and is safe to use immediately before, at, or after planting cool-season grasses. There are other preemergent herbicides available to homeowners that can be used when sodding, but realistically these should not be needed if sod is installed properly. There also are a few other preemergent herbicides that can be applied at seeding or sodding installations by professional lawn care operators.

There are several postemergent grass and broadleaf herbicides that can be used on newly established turfgrasses AFTER the turf has been mowed at least two times. If there ever was a place for homeowners to use a “point and squirt” program for weed control, it is during a spring seeded grow-in. Consult and follow the labels for all chemicals very carefully before making any of these treatments.

Summary. Cool-season turfgrass establishment is significantly more difficult in the spring than in the fall. Pay special attention to the moisture requirements and pest problems that afflict these grasses as summer approaches and by following these tips, hopefully you will successfully establish your bluegrass, fescue or ryegrass lawns.

Do you need further information? Links to Virginia Cooperative Extension publications that specifically pertain to spring lawn establishment have been provided in this podcast and are listed 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.