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Choosing Grass Varieties For Climate Zones

Pacific Sod

Because there are so many varieties of turfgrass to choose from, it can be a challenge to make sure that the turfgrass you select or recommend to your clients is the most appropriate type for their project. Choosing the proper turfgrass variety can be as important as the actual installation and maintenance of the grass itself. The type of grass you choose or recommend has an effect on almost every aspect of installation, performance and care of the turf. When turf species are planted in areas where they are not well adapted, they require greater care to grow and maintain and are more susceptible to invasion by weeds and pests.

Of all the details that should guide your recommendations regarding turfgrass, climate is arguably the most important factor to consider. Climate is the one variable that can’t be changed by your client, so it should be the first consideration in choosing or recommending turfgrass varieties. Weather and environmental factors affecting the job site should directly influence your selection. Select the turfgrass that is best adapted to the climate of the area where the grass will be planted, but don’t overlook what grass varieties are most popular and perform best in your area.

America’s varied climates allow many varieties of grasses to be used for lawns. Geographical location, soil, sun, shade, wind, rain, temperature and humidity in a particular zone can also factor into turfgrass selection on a project. Climates between zones can vary widely, so be sure you know the distinguishing weather patterns in your area. For this purpose, we will use a modified version of zone areas as follows (see map):

Zone 1: The Coastal West

Zone 2: The Western Transitional Zone

Zone 3: The Arid Southwest

Zone 4: The Intermountain West

Zone 5: The Midwest

Zone 6: New England and the Northeast

Zone 7: The Eastern Transitional Zone

Zone 8: The Central Southeast and

Zone 9: The Gulf Coast, Florida and Hawaii

To begin, turfgrass sod can be divided into cool-season and warm-season groups. Cool-season grasses can withstand cooler weather, and grow most vigorously in the fall and spring, while reducing active growth during the heat of summer. Cool-season sod types include Tall and Fine Fescues, Bluegrass, Ryegrass and Bentgrass, as well as blends and mixes of these varieties.

Fescue grasses (Genus: Festuca) may be recommended for a broad range of uses. Turf-type Tall Fescue (F. arundinacea) can handle foot traffic better than most cool-season grasses, yet in extreme wear situations, fescues will thin out significantly. Tall fescue has become a preferred grass type in transition Zones 2 and 7 because of its adaptability, but does not hold color well in freezing temperatures.

Kentucky Bluegrass (Poa pratensis) has a spreading growth pattern that is not as aggressive as warm-season varieties, but can make for a durable and healthy lawn with mild foot or pet traffic in cooler climates. Since bluegrass has a shallow root system, installing it in transition areas with hot summer will result in higher watering requirements. Bluegrass is used for showcase installations and for certain golf course application in Zone 2 despite additional irrigation needs. Since bluegrasses survive snowy winters and longer periods of cold weather better than tall fescue or ryegrass, use bluegrass for high-elevation plantings in Zones 4 and 5.

Perennial ryegrass (Lolium perenne) may also be recommended for a broad range of uses in straight ryegrass blends or bluegrass/ryegrass mixes. With fine textured blades and shiny green color year round, ryegrass lawns can be found in cooler areas of many transition zones as well as in Zones 1, 2, 4, 5, 6 and 7. Perennial ryegrass is a cool-season grass and performs best at elevations above 1000 square feet. Similar to fescue grasses, ryegrass will require more water in warmer transition areas of Zone 2 and Zone 7. Use perennial rye to over seed in transition areas with warm-season turf lawns where dormancy occurs.

Bentgrasses (Genus: Agrostis) are common in cool humid climates. Creeping bentgrass (A. stolonifera) is a fine textured perennial grass that is preferred for showcase areas or low mowing height requirements such as lawn bowling greens, putting greens and grass tennis courts. Acceptable in Zones 1, 2, 4, 5, 6 and 7, Creeping bentgrass establishes faster than Colonial bentgrass and is adapted to the fertile, low acidic, and well draining soils. It can be used to over seed bermudas in the transitional areas on golf courses. It has such an extensive maintenance regimen that it is generally not recommended for home lawns. Colonial bentgrass (A. tenuis) has lower water and maintenance requirements and a more open growth pattern, so it is more widely used on home lawns in zones favoring cool-season grasses. Colonial bentgrass is adapted to the cooler, moist areas of the northern United States and the upper shores of the Pacific and the Atlantic coastlines.

Warm-season grasses thrive in the hottest parts of the year, and go dormant when temperatures drop below 50 degrees for extended periods. Extremely cold winters can also damage or kill warm-season grass varieties.Hybrid Bermudagrass, St. Augustine, Zoysia, and Paspalum varieties are all considered warm-season grasses.

Hybrid Bermudagrass (Cynodon dactylon x Cynodon transvaalensis) is probably the best all around athletic turf for climate zones with hot summers. Its spreading growth pattern aids in resisting wear on the grass and helps repair damaged areas by spreading into injured spots. Although warm-season grasses typically go dormant in winter, an annual over-seeding program with cool-season grasses such as ryegrass or fescue can help maintain a green look to the area during the winter season.

St. Augustine grass (Stenotaphrum secundatum) is somewhat wear tolerant and can be recommended for home lawns and parks. Zoysia grasses (Zoysia japonica) have more tolerance for extreme cold and light shade than Bermuda, and much more tolerance for extreme heat and high humidity than ryegrasses, fescues and bluegrasses. It will compete well with crabgrass and other annual weed grasses in Zone 5, and usually chokes out cool-season grasses in hot, humid climates in Zone 7. Zoysia will become dormant (turn brown) with the first hard frost in the fall and green up in late April or mid-May. It is not recommended at higher elevations due to its short growing season.

Paspalums are gaining popularity in the southern U.S. Bahia grass (P. notatum) is a light green bunch type grass used in colder areas up to and including the transition zones. Its drought tolerance and its resistance to diseases and pests have made it a trendy choice. It is a fast growing grass and can require mowing every 5-7 days during summer growth months. It has a coarse look due to extensive seed head production in the summer, making this variety somewhat unattractive unless mowed frequently. Seashore paspalum (P. vaginatum) is a stoloniferous variety of turfgrass that looks similar to Hybrid Bermudagrass. The primary characteristics of Seashore Paspalums are their tolerance to high salt concentrations in soil and irrigation water. Seashore Paspalum is gaining popularity on seaside installations and on golf courses near the ocean where salinity is a factor in maintenance. Effluent and reclaimed water irrigation is also possible with this variety. Seashore Paspalums are best used in Zone 9.

Climate Zones in the United States

St. Augustine forms a dense, thick leafy sod that is recommended for shady installations, but is slow to repair, so it is normally not suggested for high traffic sports fields. Zones 2, 7, 8 and 9 are appropriate for St. Augustine lawns.

America’s varied climates allow many varieties of grasses to be used for lawns. Geographical location, soil, sun, shade, wind, rain, temperature and humidity in a particular zone can also factor into turfgrass selection on a project. Climates between zones can vary widely, so be sure you know the distinguishing weather patterns in your area. Dividing the geographic areas of the U.S. simplifies the choices for turfgrass varieties by isolating average climate factors into zones. For this purpose, we will use a modified version of zone areas as follows:

Zone 1: The Coastal West

Rain is generally plentiful in the Coastal West zone, although in the southern parts of the area it rains mostly in winter. States in this zone include western Oregon and Washington as well as most of California’s coastal communities. The summers are usually warm and dry. Most cool-season grasses are adaptable to these regions. Tall fescues are increasingly popular where summers are dry, and bluegrass is preferable where winters are cooler or at higher elevations. Ryegrass/bluegrass blends are also being used more extensively for sports fields where year round use and year round green color is required. In regions where the winters are temperate, hybrid bermudagrasses may be used with some success, and may be kept green with winter over seeding.

Zone 2: The Western Transitional Zone

Summers are generally long, dry, and warm in the Western transitional zone, which includes California’s Central Valley and most areas in Southern California’s valleys, coastline and high desert areas. Because winters are relatively mild on average you can grow either warm-season or cool-season grasses in this zone. Cool-season grasses such as tall and dwarf fescue have become the preferred lawn type in Southern California areas because the deep root system allows for lower water usage than bluegrass, ryegrass or blue/rye mixes. Fescues have year round green color that is sought after by residential and commercial customers alike in transition areas. Warm-season grasses such as Bermuda grass and Paspalum are preferable where summers are hotter and water supplies are restricted. Warm-season grasses will need to be over seeded with cool-season grasses to keep lawns green during winter.

Fescue sod varieties may have Kentucky bluegrass, fine fescues or perennial ryegrass added to the seed mix to add self-repairing characteristics or density to the sod to better tolerate traffic.

Zone 3: The Arid Southwest

The Arid Southwest zone boasts long, hot summers and relatively dry weather year-round. It includes the low elevation desert climates of California, Arizona, and New Mexico. Warm-season grasses, such as hybrid bermudas, Paspalum and zoysia are your best choices. You can over seed warm-season grasses with annual or perennial ryegrass to keep them green year-round. Plant Tall Fescues in higher elevation and mountain areas.

Zone 4: Intermountain West

Zone 4 encompasses the cold and dry areas of the West, including high-elevation areas extending to the Great Plains. From eastern California’s Sierra Nevada mountains to western Kansas and Nebraska and north to the Canadian border, Zone 4 climates in the Rocky Mountains are particularly tough, with wide fluctuations in temperature and rainfall. Tough, native grasses are often good choices. While it is possible to grow warm-season grasses in some southern areas where the winters are milder, cool-season grasses such as tall fescue and Kentucky bluegrass are preferable. Kentucky bluegrass lawns function better through harsh winters and at high elevations in this Zone than Fescue grasses.

Fine fescues such as creeping red fescue (F. rubra) have greater shade tolerance and are commonly mixed with bluegrass varieties to increase hardiness of the lawn.

Zone 5: The Midwest

The Midwest has cold, snowy winters and warm, humid summers with frequent rainfall. North and South Dakota and the Great Lakes States are part of this Zone. Cool-season grasses such as Kentucky bluegrass, and perennial ryegrass are widely planted, although you can find some hardier zoysia grass lawns in southern areas in this zone such as Illinois, Indiana and Ohio. The four most common turfgrass species used in this zone are Kentucky bluegrass, perennial ryegrass, fine fescue, and tall fescue. The first three grasses are better adapted for cooler northern part of the zone and tall fescue is more commonly used in southern areas of this zone.

Zone 6: Northeast & New England

Cold, snowy winters; warm, humid summers with frequent rain; and acidic soils are the norm in Northeastern states like New York, Massachusetts, New Jersey, and Connecticut. Cool-season grasses like fescue, Kentucky bluegrass, bentgrass and perennial ryegrass are most common. Bermuda lawns cannot withstand the winter temperatures or snow in Zone 6 and should be avoided. Zoysia grass has sufficient hardiness to survive in southern-most areas of Pennsylvania.

Bluegrass grows by shallow roots from single plants and at the same time sends out stems to form their own roots. This interweaves and supports the base making it denser as it grows, a desirable characteristic especially when choosing and recommending bluegrass-ryegrass or fescue-bluegrass mixtures. Zones 1, 4, 5, 6, and 7 are acceptable regions for bluegrass lawns.

Zone 7: The Eastern Transitional Zone

Summers are generally warm and humid in the Eastern transitional zone. The winters are mild, but can be cold, especially at higher elevations. You can grow either warm-season or cool-season grasses, but local adaptation is very important because neither warm nor cool-season grasses are perfectly matched to the states in this zone like Tennessee, Virginia and North Carolina. Bluegrasses perform better through harsh winters and in mountain regions. Tall fescues and zoysia grasses are also used in specific Zone 7 areas best suited to these varieties.

Zone 8: The Central Southeast

The Central Southeast Zone includes Georgia, Mississippi, Alabama and Northern Louisiana, as well as southern Arkansas, Oklahoma and central Texas. Zone 8 is warm and humid and gets plenty of rain. Tall fescues may be used in cooler, high-elevation areas of Zone 8, however, warm-season grasses such as hybrid bermudagrass, zoysia grass, and St. Augustine are much more appropriate in Zone 8 areas. Tall fescue is the only cool-season turfgrass that is recommended for home lawns in this zone. Warm-season turf grasses, such as Bahia grass, bermudagrass, St. Augustine, and zoysia grass grow best. You also can use cool-season grasses to over seed warm-season grasses to keep lawns green throughout winter.

Zone 9: The Gulf Coast, Florida and Hawaii

Zone 9 is comprised of southern Gulf Coast portions of Texas, Louisiana, Alabama and Mississippi, and includes all of Florida and Hawaii. Though climates are warm, humid, and wet, frequent summer rainfall and prolonged heat and humidity favor warm-season grasses in this zone. Warm-season grasses are the only grasses suited for Zone 9. Good choices include bermuda grasses, Paspalums, zoysia, and St. Augustine.

Recommend cool-season grasses in cool or moist climates, where summers are warm, but temperatures rarely stay above 90 degrees for long periods. Areas in higher elevations with adequate rainfall and coastal areas with moderate temperatures are also ideal for cool-season grasses such as fescue, bluegrass and ryegrass. Zones 1, 4, 5, and 6 are all areas where cool-season lawns are acceptable. Few cool-season grass varieties perform well in desert areas where the summers are too long and hot for cool-season grasses. Conversely, cool-season grasses grow well in areas that are generally too cold in the winter for warm-season grasses. Fescues are most widely recommended for areas that are not fully defined by specific climate zones.

In areas with hot weather, low rainfall, high winds and low humidity, landscape professionals should recommend warm-season grasses. Warm-season grasses prefer the warmer temperatures of Zones 3, 8 and 9. Hybrid bermudagrass, Paspalum, zoysia or St. Augustine varieties planted in Zones 8 and 9 will flourish in the higher temperature summers and milder winters. Planting cool-season grasses in an area better suited for warm-season grasses can result in loss of turf or significant watering issues, not to mention dissatisfied clients.

In transition zones, suggest turfgrass varieties according to the predominant microclimatic factor in each specific area. During the last decade, numerous new turfgrass cultivars have been developed and released by turfgrass seed breeders. While many of these cultivars are adapted to the environmental conditions that prevail in other regions of the country, many are not perfectly adapted to the difficult environmental conditions that occur in transition zones.

Environmental factors including weather patterns and soil types should be considered when specifying turfgrass in certain areas of Zones 2 and 7. Even non-transitional areas can have specific weather or use factors that suggest using a grass variety that is not common in that area. For example, cool-season varieties such as fescue, bluegrass and ryegrass have some aesthetic advantages in transitional zones over warm-season grasses, because they stay green year round. Where summers are warm but winters are cold, cool-season grasses can be more appropriate. When making these decisions, be sure both you and your client are aware of the drawbacks of using grasses not perfectly suited to their zone area.

Knowing the best turfgrass for each climate zone can make recommending and choosing grass types for your clients a positive experience, and can help reduce the potential for problems with installation, appearance and maintenance of the new lawn. By understanding the limitations of each zone, both you and your customers will be confident that the recommended grass type is appropriate for their zone and their project, and will provide them with the satisfaction of a beautiful new lawn.

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June 16, 2019, 10:40 pm PDT

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