Just what makes a good grass for use on an athletic field? The answer can be a bit complex, because there is no one-size-fits-all choice, and many factors must be weighed.
For starters, the grass family has about 7,500 species. Very few can survive repeated mowing. Those that can all have a crown-type growth habit, which means that the apical meristem, or growing point of the plant, remains very near the soil surface. This isn’t something created by man, but rather it’s thought that certain grasses evolved this mechanism in order to survive repeated grazing pressure by animals.
Of these crown-type grasses, about 45 possess agronomic qualities that make them desirable as turfgrasses. Among these characteristics are the ability to form a turf with high shoot density and a medium-to-fine texture; many of them produce lateral shoots and, therefore, can spread relatively rapidly. Examples include Kentucky bluegrass (a cool-season turf species) and bermudagrass (a warm-season turf species).
Other species that tolerate low mowing heights do not have agronomic qualities that merit use as a turfgrass (such as quackgrass, orchardgrass, crabgrass and goosegrass) and often present as weeds.
These 45 turfgrass species have different agronomic characteristics that influence their suitability in a given area. Some are ideally suited for use as a grass on golf course putting greens, such as creeping bentgrass. However, what makes creeping bentgrass great for use on a putting green is its ability to tolerate very low heights of cut. If creeping bentgrass were used on an athletic field, the results would be rather disastrous because bentgrass, among other problems, lacks tolerance to heavy traffic.
Other species of turfgrass have proved poorly suited for athletic fields. Rough bluegrass, for example, has stolons but it’s not as aggressive as Supina bluegrass or Kentucky bluegrass. In addition, it has limited wear tolerance and tends to go dormant very early in the summer. The fine fescues also lack sufficient wear tolerance to survive on athletic fields.
Ideally, the athletic turf grasses should possess the following characteristics:
- The ability to tolerate heavy traffic;
- The ability to recover quickly from injury;
- They should germinate and establish rapidly from seed;
- They should have good annual color, meaning both the ability to grow at lower temperatures and some tolerance to heat and drought stress.
That said, there’s no perfect grass for an athletic field because no species possesses all of these characteristics. But most grasses used on sports fields possess at least two of them, and often the species may be mixed in order to try to increase the number of criteria satisfied.
The main athletic field turfgrasses in the northern parts of the country are Kentucky bluegrass, perennial ryegrass and tall fescue. The decision to choose one species over the other may not be clear, because each grass has its strengths and weaknesses. Kentucky bluegrass it’s not as wear-tolerant as tall fescue. Tall fescue doesn’t establish as rapidly as perennial ryegrass. Perennial ryegrass doesn’t recuperate from injury as well as Kentucky bluegrass. Thus, proper selection should take into consideration factors such as type and frequency of play, the environment and soil type, the level of performance expected and available management inputs.
Kentucky bluegrass is fine-textured and produces a high-quality, long-lasting playing surface. Kentucky bluegrass also produces rhizomes, thus it has the ability to spread laterally more quickly than bunch-type turfgrasses.
This is important because areas that have been worn down by play or insects, and diseases, are filled in more quickly. Kentucky bluegrass also withstands temperature and moisture extremes comparatively well. An important characteristic in the northern tier of states is that Kentucky bluegrass has better winter hardiness compared with either tall fescue or perennial ryegrass.
Kentucky bluegrass does have disadvantages. It requires evenly moist, well-drained soil for best performance. The species isn’t tolerant of extremes in soil pH. Also, while the species has evolved a mechanism to make it able to survive and recover from extended periods of heat and drought, it’s one of the first species to experience color and/or loss of quality and go dormant during the summer. If the field is shaded for several hours a day (as would occur primarily in large, major league facilities), then Kentucky bluegrass is quite intolerant. Kentucky bluegrass is susceptible to several cosmetic diseases such as powdery mildew and leaf spot but also to more serious diseases such as necrotic ring spot.
Another serious issue with Kentucky bluegrass is that its germination and establishment rates are very slow. Germination can take from 10 to as long as 28 days, depending on weather conditions. Even after germination, the establishment rate of the species is amongst the slowest of the turfgrasses. It can take nine months or more for Kentucky bluegrass to produce an acceptable sports turf surface from seed.
Most of the time, improved cultivars of Kentucky bluegrass are used on athletic fields because they have superior texture and density, and can be mowed at lower heights of cut. But these cultivars are not for use on low-maintenance fields. The improved Kentucky bluegrasses require routine applications of fertilizer, perform best as sports turfs when mowed around 1.25 to 2 inches and, when used on sports fields, require irrigation for best performance during the summer months.
In a lot of ways, perennial ryegrass is very different from Kentucky bluegrass. But this can make perennial ryegrass a good grass to grow in a mix with Kentucky bluegrass. It has a bunch-type growth habit that limits its recuperative potential. Like Kentucky bluegrass, perennial ryegrass requires moist, well-drained soil for best performance. Also, best growth is in soils that are neutral to slightly acidic.
It has only middle-of-the-road tolerance of hot conditions and poor tolerance to drought. It might take a bit longer for it to go off-color compared with Kentucky bluegrass. But, once it does, it takes a lot longer for it to come out of drought dormancy.
It has middle-of-the-road tolerances to shade and soil salinity. There are tough fibers in the leaf of perennial ryegrass, which, on one hand, give it better wear tolerance compared with Kentucky bluegrass. On the other, these fibers cause the quality of cut to be lower or, at a minimum, more care has to be taken to ensure that mower blades are adequately sharpened.
Perennial ryegrass may contain endophytes, which are symbiotic fungi that improve resistance to certain insects, such as bluegrass billbug. However, perennial ryegrass is susceptible to many diseases. Some of them, such as red thread, are mainly cosmetic. However, brown patch and pythium can be a serious issue.
Perhaps more serious is grey leaf spot. This disease might not occur as frequently due to the conditions that are required for its development. But there are no curative fungicides for this disease and most athletic field managers deal with grey leaf spot (or its potential development) by applying a program of fungicides that are in differing chemical classes.
Despite these weaknesses and limitations, perennial ryegrass is a very important species for athletic field management. The reason for its widespread use is its very rapid seed germination, which can be in as little as three to four days. In addition, perennial ryegrass establishes much more rapidly than Kentucky bluegrass. Because of this and its fine textured appearance, perennial ryegrass often is mixed with Kentucky bluegrass at establishment.
Or, what also often happens is that a field is established in Kentucky bluegrass and then overseeded with ryegrass so that, over time, the field gradually becomes a mixture of the two species.
Tall fescue is, by far, the most wear-tolerant of the cool-season turf species. It’s also, by far, the most tolerant of drought. In addition, tall fescue has fewer issues with insects and diseases and tends to out-compete weedier species than bluegrass or ryegrass. It’s also tolerant of low fertility. For a low-maintenance athletic field or a field with relatively limited play, tall fescue can be a good choice.
Tall fescue isn’t used more on high-end sports surfaces because, though it is wear-tolerant it will wear, and its germination and establishment aren’t as rapid as that of perennial ryegrass.
Tall fescue has rhizomes as a recessive trait, so it’s considered a bunch-type species, like perennial ryegrass, and this limits its ability to recover from injury. Some cultivars display more rhizome activity than others. But rhizome development in a full stand of turf or when grown in clay-based soil isn’t as evident as when grown in low density or on sand.
Even without severe traffic pressure, tall fescue fields often will need periodic overseeding in order to maintain good density. Tall fescue can be mixed with Kentucky bluegrass so long as the tall fescue is the dominant species.
The main turfgrass for athletic fields in the southern parts of the U.S., it has the best wear tolerance of any turfgrass. It establishes very rapidly and recovers very rapidly from injury due to the aggressive nature of its stolons. Unfortunately, it lacks the cold tolerance necessary to persist in northern parts of the U.S. Common bermudagrass lacks the density, cold hardiness, and, in some cases, disease resistance of hybrid bermudagrass.
A major advantage of its use is that common bermudagrass can be seeded. There are improved common-type bermudagrass cultivars that are darker green, more finely textured and denser compared with common bermudagrass. The common bermudagrasses, though, tend to be used for fields that are low- to medium-maintenance.
Bermudagrass cultivars used on high-maintenance athletic fields tend to be hybrids, including Tifway and TifSport. They are established vegetatively, either by sod or sprigs and grow rapidly. There have been developments in cultivars with more cold tolerance.
So, which to choose?
Ultimately, this is based on the field’s location. Also, as simplistic as this may sound, often the best choice may be what others within close proximity to you are using.
In the South, in rare instances, bahiagrass or seashore paspalum may be used, but, more often than not, the choice is bermudagrass.
In the North, in many cases, the decision comes down to Kentucky bluegrass or perennial ryegrass. Both are aesthetically similar.
Another factor to consider is that perennial ryegrass can be cut at a lower height, which can be an advantage for sports such as soccer. However, Kentucky bluegrass provides better traction. Some say that ryegrass is “slippery” because the backside of the leaf is shiny. What’s more likely is that bluegrass produces rhizomes, which, in turn, produces more thatch both of which provide better traction.
The bottom line is that, if Kentucky bluegrass germinated and established as rapidly as perennial ryegrass, there would be no need for perennial ryegrass. But, because of its rapid germination and establishment, ryegrass is almost always a component on an athletic field.
Hundreds of cultivated varieties of Kentucky bluegrass are available. There are many cultivars of ryegrass and tall fescue. An important consideration when choosing cultivars, however, is that the bluegrass cultivars are categorized by agronomic characteristics, such as the compact types or the aggressive types.
It sometimes can be a bad idea to mix cultivars from the different groups because the growth characteristics will be too different, resulting in the same segregation problems that we see when mixing incompatible species.
The best-performing cultivars often vary by location, so be sure to consult extension literature.
It is best to blend three to five cultivars if one species of grass is established. If a mix of grasses is being used, two cultivars of each species are best. This will offer diversity and, perhaps, resistance to certain insect and disease pests.
PHOTOS: DAVID GARDNER, PH.D. AND ISTOCK