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Grass as a functional element: erosion control

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Nothing makes a better first impression about your home and landscape than a healthy green lawn. In fact, in most landscapes, both residential and commercial, much of the estate is taken up by turfgrass. When planning a lawn, we need to consider the proper balance of lawn versus other landscape treatments, the benefits of lawn, and the type of turfgrass that s appropriate for your area based on soil conditions, light and climate.

The Balance of lawn versus other landscape treatments.

You will find that the lawn looks its best when it is in proper balance with other landscape treatments. Trees, shrubs, flower gardens and even hardscape features like patios and walkways all have a part in the landscape design.

As a general rule, plan your lawn areas to occupy about 50% of the total landscape area. First, determine the location of decks, patios and walkways. Next, establish the bed areas around the house foundation and at strategic viewing areas such as dining room windows, deck and patio areas. Select the appropriate evergreen screening trees to frame of block these views. Once these are determined, then lay out your lawn areas. One way to do this is to imagine the beds as islands  and the lawn as water . Use curvilinear forms so that the whole landscape has flow and interest. Try using a hose or rope to visualize these areas.

Benefits of Turfgrass

The actual and perceived benefits of turfgrass are*:

Functional

• Soil erosion control
• Dust Prevention
• Rain Water entrapment
• Solar heat dissipation
• Glare reduction
• Organic chemical pollutant entrapment and degradation
• Fire prevention
• Security

  Recreational

• Low-cost surfaces
• Physical health
• Mental health
• Safety cushion
• Spectator entertainment

  Aesthetic

• Beauty
• Quality of life
• Mental health
• Social harmony
• Community pride
• Increased property values
• Complements trees and shrubs in the landscape

*Dr. J.B Beard and Dr. R.L. Green in the Journal of Environmental Quality, June 1994.

Type of Turfgrass

Turfgrass lawns can be categorized into one of two types: cool season grasses and warm season grasses. The environmental condition of the site is the most important consideration in choosing the right type of turfgrass. The determining factors are temperature, moisture, light and soil.

Cool Season Grasses

Cool season grasses are green year-round and are generally found in cooler climates. They generally propagate by seed, are not invasive, and are the best performers in shady areas. Fescue, rye and bluegrass are the most common winter season turfgrasses.
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Fescue (Festuca arundinacea): There are several hybrids of fescue on the market today, most derived from Kentucky-31 tall fescue. Fescue offers one of the best values in lawns; it can be established by seed or sod at relatively low cost and does fairly well in clay soils. It has a medium wide, soft blade and offers year-round green. It does well in light shade. Consequently, it is the turfgrass of choice for home-builders. However, it requires a relatively high amount of maintenance: in the growing season, it must be mowed weekly, fertilized quarterly and acid soils amended with lime to ensure proper PH for intake of nutrients. It requires irrigation, particularly in summer, and is susceptible to summer heat and drought.

Rye

Rye (Lolium perenne, L. multiflorum): The ryegrasses are best adapted to moist, cool environments where temperatures are not extreme in the winter or summer. Many European countries have climates ideally suited to the ryegrasses. In the United States, the northeastern and northwestern states are well suited to ryegrass. In the south, perennial ryegrass is unsuitable as a permanent turfgrass. But both species serve as cool season annuals. For an instant lawn, nothing can be the bright green of annual rye. At the first sign of heat, however, it bolts and dies off. It is often mixed with fescue for erosion control applications and over-seeded on summer season grasses for that green look during the winter. When it starts to die off, the summer season grasses are starting to green up giving a year-round green lawn.

Bluegrass

Bluegrass (Poa pratensis): Probably the most outstanding feature of Kentucky bluegrass is its unusually dark blue-green color. Its high density provides a thick carpet that will stand up to the abuses of athletic fields and high traffic. Sod producers and homeowners alike enjoy its dwarf growth characteristics which result in fewer mowings and lower maintenance costs. This outstanding cultivar shows good resistance to leaf spot and stem rust, stripe smut and dollar spot. University trials have documented heat and drought tolerance. Bluegrass performs well in sand or heavy clay soils, and performs best in soils with a pH of 5.5 to 8.0. Three to five lbs. N/1000 sq. ft./year is adequate in most areas of the United states. Similar in appearance to fescue, bluegrass is sometimes mixed with fescue to impart some of its drought tolerant characteristics to the lawn.

Kentucky bluegrass is native to practically all of Europe, northern Asia and the mountains of Algeria and Morocco. Although the species is spread over all of the cool, humid parts of the U.S., it is not native to North America. In the southern U.S., Kentucky bluegrass is limited to the transition zone from North Carolina, through much of Tennessee, northern Arkansas to the panhandle of Texas and Oklahoma. In the western states, Kentucky bluegrass is grown with irrigation.

Warm Season Grasses

Warm season grasses have characteristics that are opposite from the cool variety. They are generally found in warmer climates, go dormant in the winter in transitional areas, propagate by rhizomes as well as seed (and consequently are considered invasive) and do best in sunny areas. The most common summer season grasses are Bermuda, Centipede, Zoysia and St. Augustine.
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Bermuda (Cynodon dactylon): Bermuda has a fine blade and is often found on the golf course. Here its heat and drought tolerance and relative durability to traffic are major assets. It can be found in some residential lawns, but here its invasive characteristics are problematic as it tends to spread into flowerbeds. Bermuda does not need to be cut as often as fescue, but should be cut shorter (1  vs. 4 ) to promote a more vigorous lawn. As a consequence, ground preparation and leveling are more critical to prevent scalping by lawn maintenance equipment. Bermuda only requires fertilizing once per year and can subsist without irrigation. Lawns can be established by seed or by sod at a cost that is comparable to fescue. Drawbacks: it cannot be grown in shade.

Centipede (Eremochloa ophiuroides): Centipede is low growing, creeping perennial grass with medium leaf width which spreads by short jointed thick stolons. It is heat and drought tolerant and tolerates light traffic. It can be found in some residential lawns, and is somewhat invasive, but not nearly as much as Bermuda. Like Bermuda, it only needs to be cut half as often as fescue, but should be cut shorter to promote a more vigorous lawn. As a consequence, ground preparation and leveling are more critical to prevent scalping by lawn maintenance equipment. Centipede also only requires fertilizing once per year and can subsist without irrigation. It can be grown in sandy or clay soils with adequate moisture and full sunlight. While it is possible to find seed, it is more common to establish a centipede lawn with sod or plugs. The cost of sod is roughly double that of Bermuda.

Zoysia (Zoysia Japonica): Zoysia is the Cadillac of summer season grasses. It is the most like fescue in appearance with soft blades. It has a reputation for becoming the dominant turfgrass where it is introduced. Lawns are generally established by sod or plugs. It is the least invasive of the summer season grasses, while possessing good drought and heat tolerance. It likes a well-drained soil and full sun.

St. Augustine (Stenotaphrum secundatum): St. Augustine is the grass of choice for a coastal environment. It is salt tolerant and likes well-drained, sandy soil and full sun. Its blades are the coarsest of the summer season grasses. This grass usually crowds out other grasses and weeds due to the dense sod production. It is moderately invasive. While it is very drought and heat tolerant, it will also thrive in shade. Lawns are generally established by sod at a cost comparable to zoysia.

The following table illustrates the strengths and weaknesses of the various types of lawn:

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