“Fall” Into your Cool-season Lawn: Selecting the Best Grass
Shorter days and cooling temperatures signal the change in seasons, ushering in the ideal period in Virginia to establish cool-season turfgrasses (bluegrasses, fescues, and ryegrasses). This podcast considers the strengths and weaknesses of the cool-season grasses that will help you make the best possible selection for your site.
Whether you are facing establishment of a new lawn or renovation of an existing one, the late summer to early fall months offer the ideal time to seed and sod cool-season turfgrasses. What are the choices in cool-season turfgrasses that provide the best opportunity for success?
I’m going to arbitrarily divide Virginia into three general regions for this podcast. Working from west to east, we will have the Valley and Ridge region of SW and NW Virginia, the Piedmont or central region of the state, and the eastern region is the Tidewater. Since we run from the mountains to the sea across this great state, your work is cut out for you in finding that “perfect” turfgrass-- it simply does not exist given our climate. However, I’ll do the best I can to describe the strengths and weaknesses of our predominant cool-season turfgrasses and detail where they likely best fit in these regions.
Depending on your site, perhaps a turfgrass isn’t even the best choice?
I know… this is a sacrilegious statement coming from a turfgrass scientist, but it is true—when light is highly limiting due to shade, there really isn’t a lot available when it comes to turfgrasses. We will discuss the relative differences in shade tolerance of the grasses shortly, but as a general rule of thumb, if your site only receives 3-4 hours of filtered light per day, you will likely be better served to install planting beds that feature shade-tolerant ground covers and ornamentals. Remember: grasses evolved in “grasslands”—what’s missing? Trees!
Basic descriptions of the predominant cool-season grasses.
Kentucky bluegrass. One of the prettiest cool-season turfgrasses available due to its genetically dark-green color and fine-medium leaf blade. This grass has exceptional cold tolerance, an aggressive lateral growth habit due to rhizomes, and features a “summer dormancy” mechanism to survive extreme environmental periods. It is a “full sun” turfgrass and does very poor where it receives less than 6 hours of full sun per day. Bluegrass responds to an aggressive maintenance program of up to 4 lbs N/1000 sq ft on an annual basis. Due to the aggressive N program and its rhizomatous growth habit, it likely will have to be dethatched (i.e. vertical mowed) every 2-3 years. It tolerates regular mowing at 1.5 to 2 inches. Kentucky bluegrass has sporadic concerns with insect and disease pests, with the two of most concern typically being grubs and summer patch. This grass is well adapted to the Valley and Ridge and the northern Piedmont, and is not adapted to southern Piedmont and Tidewater. Optimal soil and moisture conditions result in seed germination within 14-21 days.
Tall fescue. Turf-type tall fescues have been selected for finer leaf texture and improved density. This grass is by far the most prevalent lawn grass in terms of acreage in Virginia because it is simply a very hardy, very durable grass. It is managed as a bunch-type grass, although the recent release of rhizomatous tall fescues is attracting a lot of attention. Tall fescues have the deepest root systems of any cool-season turfgrass, allowing them to utilize water from deep in the soil. They have moderate shade tolerance that suits them well in some of our hottest locations. Since breeding efforts have resulted in finer leaf textures and less clumping tendency it is now commonplace that most sod farms market almost exclusively tall fescue/Ky bluegrass mixtures (90/10% by weight) because of their similarity in appearance. These combinations increase genetic diversity, thus improving the chances of the turf surviving environmental or pest pressure. Tall fescue is flexible in terms of typical annual N requirement, with anywhere from 2-4 lbs/1000 sq ft possible. There should be no thatching problem in a properly managed tall fescue lawn. It requires a 2-3 inch regular cutting height, and performs best in the summer by mowing it even taller. By far the major pest of regular importance is Rhizoctonia blight (brown patch). Tall fescue is well adapted to the Valley and Ridge and the Piedmont regions of Virginia, and is marginally adapted to the Tidewater. Optimal conditions result in seed germination in 5-7 days.
Fine-leaf fescues. There are three species of fine-leaf fescues used in Virginia: hard, chewings, and creeping red. Hard and chewings fescues are true bunch-type grasses, while creeping red has very short rhizomes. They are all managed as bunch-type grasses. The needle-like leaves are very distinctive of these species, and for most practical purposes, all species perform comparably in our climate. This is by far the most shade-tolerant cool-season turfgrass, providing acceptable turf density with as little as 3-4 hours of sunlight per day. The fine-leaf fescues are noted as being the “poor folk’s” grass of the north and any more than 2 lbs of N/1000 sq ft on an annual basis will actually create problems in most landscapes due to increased pest and environmental stress pressures. Sun/shade seed mixtures of fine fescue and Kentucky bluegrass are commonly found on the shelves of lawn and garden centers, and over time, the lawn segregates into fine fescue in the shade and bluegrass in the full sun. Fine fescues will tolerate 1.5-2.5 inch regular cutting heights, but these grasses are relatively slow growers, so it is common that they are mowed at taller heights in lower maintenance lawns. These species do not tolerate poorly drained soils. This grass is well adapted to both full and partial sun conditions in the Valley and Ridge, shaded-only conditions in the northern Piedmont, and is not adapted in most situations in the southern Piedmont and Tidewater. Optimal soil conditions lead to seed germination rates of 14-21 days.
Perennial ryegrass. This grass is not often planted as a monostand, but instead is a component of many commercially available seed mixtures with Kentucky bluegrass and bluegrass/fine fescue. Perennial ryegrass is a bunch-type grass, but is noted for outstanding wear tolerance when it matures. Most cultivars have exceptional dark green color and the waxy leaves of perennial ryegrass make it a very attractive turf when mowed due to its “striping” effect (i.e. the way the light reflects off the leaves). It is fine-bladed and matches up well with Kentucky bluegrass in terms of leaf texture, hence bluegrass/ryegrass seed combinations are very common. A major advantage of perennial ryegrass for turf establishment is its very rapid germination rate from seed, 4-7 days under optimal conditions. Perennial ryegrass typically struggles with summer-time pest and environmental stresses and for these reasons it is not normally planted by itself. It is best adapted as a monostand at elevations above 2000 ft in the Valley and Ridge, and can be used successfully in mixtures with bluegrass and fine-fescue in the rest of the region and in the northern Piedmont. It is usually only grown as a winter annual in the southern Piedmont and Tidewater regions, and is most often used for winter overseeding of warm-season grasses. It is a rapid growing grass and is the most tolerant of close clipping (regular heights as low as ¾ inch are possible), but such mowing requires a reel mower.
Hybrid bluegrass? A summer 2006 podcast detailed where this new grass might fit into Virginia’s lawns. Please consult the list of podcasts on the Turf and Garden Tips archives for a full discussion of Virginia Tech’s research findings so far regarding hybrid bluegrass.
So if these are my choices in species, what cultivars should I be looking for? Virginia Tech partners with the University of Maryland in the development of an annual “recommended turfgrass variety list”. Since our states have such difficult climates to work with, it benefits both of us to combine our performance data that considers a broad range of climatic conditions. This list is provided on this podcast webpage, but the current list can always be found at the extension publications and resources website. Cultivars that make the list are in one of two categories: Recommended (meaning it has performed a minimum of at least 3 consecutive years in our top statistical category at both locations) or Promising (a minimum of at least 2 consecutive years in our top performing category). Now, finding these cultivars at the lawn and garden center of many of the giant retailers is no sure thing; these vendors almost always purchase seed on a volume basis and not according to regional recommendations. So, you might have to consult with smaller, more specialized turf and garden distributors to locate these cultivars. Also, it is important to understand that just because a cultivar is not on our recommended list does not mean it is going to fail. Our data only pertain to those cultivars contained within our field trials and there are likely numerous high quality cultivars on the market that we are not currently evaluating.
Shop for Certified Plant Material.
You will note that most of the recommended and promising cultivars you find will be available as CERTIFIED (i.e. blue tag) seed. Blue tag seed is your assurance that the seed on the tag is actually in the bag. It is no guarantee of success, but it is certainly worth paying a few pennies more per pound knowing that you are purchasing the highest quality product possible. The Virginia Crop Improvement Association also runs a sod certification program and a list of certified sod producers can be found at www.VirginiaCrop.org.
Hopefully, this information will serve as a starting point for you in selecting the best cool-season grass for your situation. Look for other podcasts on this website that pertain to cool-season turfgrass establishment and let your local Virginia Cooperative Extension office know how it can assist you in your quest for a great looking, environmentally responsible lawn.