Lawns are a standard feature of ornamental private and public gardens and landscapes in much of the world today. Lawns are created for aesthetic use in gardens, and for recreational use, including sports. They are typically planted near homes, often as part of gardens, and are also used in other ornamental landscapes and gardens.
Lawns are frequently a feature of public parks and other spaces. They form the playing surface for many outdoor sports, reducing erosion and dust as well as providing a cushion for players in sports such as football, cricket, baseball, golf, tennis, bocce and stake. In sports venues, the word lawn is often replaced by turf or green.
Many different species of grass are used, often depending on the intended use of the lawn, with vigorous, coarse grasses used where active sports are played, and much finer, softer grasses on ornamental lawns, and partly on climate, with different grasses adapted to oceanic climates with cool summers, and tropical and continental climates with hot summers. It is also not uncommon to mix grass seeds. A 50/50 mixture of grass types can, for example, form a stronger lawn when one grass type does better in the warmer seasons and the other is more resistant to colder weather.
Types of Lawngrass
There are thousands of varieties of lawngrass, each adapted to specific conditions of precipitation, temperature, and sun/shade tolerance. Breeders are constantly creating new and improved varieties of the base list of lawngrass species. The two basic categories are cool season grasses and warm season grasses.
Cool season grasses start growth at 5 °C, and grows at their fastest rate when temperatures are between 10-25 °C (Huxley 1992), in climates that have relatively mild/cool summers, with two periods of rapid growth in the spring and fall. They retain their color well in extreme cold and typicaly grow very dense, carpetlike lawns with relatively little thatch.
Warm season grasses only start growth at temperatures above 10 °C, and grow fastest when temperatures are between 25 °C and 35 °C, with one long growth period over the spring and summer (Huxley 1992). They often go dormant in cooler months, turning shades of tan or brown. Many warm season grasses are quite drought tolerant, and can handle very high summer temperatures, although temperatures below -15 °C can kill most warm season grasses.
Maintaining a rough lawn requires only occasional cutting with a suitable machine, or grazing by animals.
Higher quality lawns however require a number of operations. These may include:
- Mowing, to cut the grass regularly to an even height
- Mow your lawn frequently
- Leave the grass clippings to decompose on the lawn. Annually, this will provide nutrients equivalent to one or two fertilizer applications. Set mower at 2 inches to reduce water use during hot weather.
- Scarifying and raking, to remove dead grass and prevent tufting
- Rolling, to encourage tillering (branching of grass plants), and to level the ground
- Top dressing the lawn with sand, soil or other material
- Spiking or aeration, to relieve compaction of the soil
- Watering, to prevent from going dormant and turning brown
- Early moring or night is the best time for watering to reduce evaporation.
- To help control where your water goes, water when it's not windy.
- One deep watering is much better than watering several times lightly.
- Lawns need about 1 inch of water each week. If the weather is very hot, apply an inch of water about every 3 days.
- Watering to a depth of 4-6 inches encourages deeper, healthier root development. It allows longer periods between watering.
- To measure the water, put an empty tuna can (or cat food can) on the lawn while watering. Stop watering when the can is full or if you notice water running off the lawn.
- Test your soil to find out what nutrients ar needed. Contact your local Natural Resources Conservation Service or Cooperative State Research, Education, and Extention Service office to get information on obtaining a soil test. Local fertilizer dealers can also be helpful.
- A soil test will help you understand what your plants require.
- Follow label directions.
- Choose a fertilizer that has at least one-fourth of the nitrogen in a slow-release form, such as sulpher-coated urea.
- It is best to apply fertilizer when the soil is moist and then water lightly. This will help the fertilizer move into the root zone where it is available to the plants, rather than stay on top of the soil where it can be blown or washed away.
- Watch the weather. Avoid applying it immediately before a heavy rain system is predicted to arrive. Too much rain (or sprinkler water) will take the nutrients away from the lawn's root zone.
- Use the minimal amount of fertilizer necessary and apply it in small, frequent applications. An application of 2 pounds of fertilizer five times per year is better than 5 pounds of fertilizer twice a year.
- Calibrate your fertilizer spreader to be sure you know exactly how much material is being discharged in a given space. Follow instructions accompanying your spreader.
- When spreading fertilizer, cover ends of the lawn first, ten go back and forth across the rest of the lawn, using half of the recommended amount. Shut the spreader off before reaching the ends to avoik over-application. Apply the other half of the fertilizer going back and forth perpendicular to the first pattern.
- Dispose of fertilizer bags or containers in a safe and state-approved manner.
- Pesticide application to manage weeds and insects
- Different soil types have different watering needs. You don't need to be a soil scientist to know how to water your soil properly. These tips can help.
- Loosen the soil around plants so it can quickly absorb water and nutrients.
- Use a 1- to 2-inch protective layer of mulch on the soil surface above the root area. Cultivating and mulching reduce evaporation and soil erosion.
- Clay soil: Add organic material such as compost or peat moss. Till or spade to help loosen the soil. Since clay soil absorbs water very slowly, water only as fast as the soil absorbs the water.
- Sandy soil: Add organic material to supplement sandy soil. Otherwise, the water can run through it so quickly that plants won't be able to absorb it.
- Loam soil: The best kind of soil. It's a combination of sand, silt, and clay. Loam absorbs water readily and stores it for plants to use.
Fertilizers provide nutrients necessary for plant health and growth, such as nitrogen, phosphorus, and potassium. These are what N, P, and K stand for on bags of fertilizer. Nitrogen (N) is needed for healthy green growth and regulation of other nutrients. Phosphorus (P) helps proper roots and seeds develop and resist disease. Potassium (K) is also important in root development and disease resistance. When properly applied, the nutrients in fertilizers are absorbed by plants and little of these nutrients enters ground or surface water resources.
Seasonal Lawn Maintenance
Seasonal lawn care will vary to some extent depending on the climate zone and type of grass that is grown, whether cool season or warm season varieties. In general, however, there are recognized steps in lawn care that should be observed in any of these areas.
Spring or early summer is the time to seed, sod, or sprig a yard, when the ground is warmer. For a new lawn, adding a fresh load of topsoil to the ground is beneficial. Seeding the lawn is the least expensive way to plant, but it takes longer for the lawn to grow and usually needs daily watering, or the freshly-sprouted grass will die. Sodding is more expensive, but it will provide an almost instant lawn that can be planted in most climate zones in any season. Hydroseeding is a relatively quick and inexpensive method of planting. A nitrogen-based, slow-release fertilizer should be applied, as well as a weed killer and a product for lawn pest removal.
Summer lawn care requires raising the lawn mower for cool season grass, and lowering it for warm season lawns. Lawns will require longer and more frequent watering, best done in early morning to encourage a stronger root system. This is also the time to apply an all-purpose fertilizer. During the hot summer months, lawns may be susceptible to fungus disease. It’s advisable to take a sod sample to a local landscape expert for testing and treating the yard, if necessary.
In the fall, lawns can be mowed at a lower height and thatch buildup that occurs in warm season grasses should be removed, although lawn experts are divided in their opinions on this. This is also a good time to add a sandy loam and apply fertilizer, one that contains some type of wetting agent. Cool season lawns can be planted in autumn if there is adequate rainfall.
Lawn care in the winter is minimal, requiring only light feedings of organic material, such as green-waste compost, and minerals to encourage earthworms and beneficial microbes.
A number of criticisms of lawns are based on environmental grounds:
- Many lawns are composed of a single species of plant, or of very few species, which reduces biodiversity, especially if the lawn covers a large area. In addition, they may be composed primarily of plants not local to the area, which can further decrease local biodiversity.
- Lawns are sometimes cared for by using pesticides and other chemicals, which can be harmful to the environment if misused.
- Maintaining a green lawn often requires large amounts of water. This was not a problem in temperate England where the concept of the lawn originated, as natural rainfall was sufficient to maintain a lawn's health. However the exporting of the lawn ideal to more arid regions of the world, such as the U.S. Southwest, has crimped already scarce water resources in such areas, requiring larger, more environmentally invasive water supply systems. Grass typically goes dormant during cold, winter months, and turns brown during hot, dry summer months, thereby reducing its demand for water. Many property owners consider this "dead" appearance unacceptable and therefore increase watering during the summer months. Grass can also recover quite well from a drought.
- In the United States lawn heights are generally maintained by gasoline-powered lawnmowers, which contribute to urban smog during the summer months. The U.S. Environmental Protection Agency found that in some urban areas, up to 5% of smog was due to pre-1997 small gasoline engines such as are typically used on lawnmowers. Since 1997, the EPA has mandated emissions controls on newer engines in an effort to reduce smog. 
- Lawns use up vast areas of arable land that might otherwise be used for growing crops.
However, using ecological techniques, the impact of lawns can sometimes be reduced. Such methods include the use of local grasses, proper mowing techniques, leaving grass clippings in place, integrated pest management, organic fertilizers, and introducing a variety of plants to the lawn.
In addition to the environmental criticisms, some gardeners question the aesthetic value of lawns.
One positive benefit of a healthy lawn is that of a filter for contaminants and to prevent run-off and erosion of bare dirt. Highway construction projects in the United States now routinely include replanting grasses on disturbed soils for this purpose, although they are not maintained as lawns.
- Artificial turf
- Organic lawn management
- Lawn mower
- Tree lawn
- No-dig gardening
- Artificial lawn
- Looking for Lawns - a general interest article about the NASA study
- Huxley, A., ed. (1992). Lawns. In New RHS Dictionary of Gardening 3: 26-33. Macmillan. ISBN 0-333-47494-5
- Jenkins, V. S. (1994). The Lawn: A History of an American Obsession. Smithsonian Books. ISBN 1-56098-406-6
- Steinberg, T. (2006). American Green, The Obsessive Quest for the Perfect Lawn. W.W. Norton & Co. ISBN 0-393-06084-5
- Small Engine Emission Standards: FAQ for Dealers and Distributors - U.S. EPA (PDF format)
- Hobby Lawn Care - Various articles on seasonal lawn maintenance