Grass, the most useful family of plants. There are more than 5,000 kinds of grasses. Some grow only about one inch (2.5 cm) high while othersthe bamboosreach 100 feet (30 m) or more. They grow in ordinary soil, in or near water, in deserts, and even in Arctic wastelands. Many provide humans and animals with a large part of their food needs. Other grasses are grown for lawns. Still others are used as soil-builders, to help control erosion, or in making such products as paper, cloth, and perfumes. Many grasses are simply weeds.

Most grasses are annual or perennial herbaceous plants, but the bamboos and a few other species have woody stems. The culms, or stems, of grass are cylindrical and jointed. The leaves grow singly on opposite sides of the stem. Each leaf consists of two partsthe sheath and the blade. The sheath, or base of the leaf, encircles the stem just above the node, or joint. The spear-shaped, parallel-veined blade rises from the sheath at a sharp angle.

The root system of annual grasses is a simple, branching cluster of hairlike rootlets. Perennial grasses often spread by means of rhizomes (underground rootlike stems) and form sod. The flowers of grass are usually clustered in spikelets; the fruit is a caryopsis (a dry, one-celled grain).

Common grasses
Bermuda grass (Cynodon dactylon) is used for hay, lawns, general-purpose turf, and erosion control. The plant has rhizomes and stolons from 2 inches (5 centimeters) to more than 20 feet (6 meters) long. The grass generally grows from 6 to 12 inches (15 to 30 centimeters) tall.
Blue grama (Bouteloua gracilis) can withstand drought and is used for grazing and erosion control. The plant grows from 1 to 2 feet (30 to 61 centimeters) high and is very leafy at the base. It has narrow blades.
Buffalo grass (Buchloe dactyloides) forms a thick gray-green sod and spreads by stolons. It grows from 4 to 6 inches (10 to 15 centimeters) high and can be identified by its burrlike female flower cluster. Buffalo grass can withstand heavy grazing.
Crested wheatgrass (Agropyron cristatum) is widely used for grazing on rangelands. It can withstand drought and thrives in cool weather. It grows in bunches with culms from 10 to 40 inches (25 to 100 centimeters) high. The blades measure from 6 to 10 inches (15 to 25 centimeters) long. The flower clusters grow from 2 to 3 inches (5 to 8 centimeters) long.
Kentucky bluegrass (Poa pratensis) is a valuable and widely grown pasture and lawn grass. It grows from 1 to 2 1/2 feet (30 to 76 centimeters) high. The tip of the blade is curved in the shape of a bow of a boat. Rhizomes spread out from the plant to start new plants.
Little bluestem (Schizachyrium scoparium) grows from 2 to 4 feet (0.6 to 1.2 meters) high and has narrow flat leaves 4 to 8 inches (10 to 20 centimeters) long. The blades are green when young, but turn reddish-brown when the plant matures.
Orchardgrass (Dactylis glomerata) is grown for hay and pasture. It is one of the first grasses to turn green in the spring, providing early grazing. It grows in bunches with stems 2 to 4 feet (0.6 to 1.2 meters) high. It can be identified by its tightly clustered flowers.
Smooth brome (Bromus inermis) is used for hay and pasture. It spreads by rhizomes and grows from 3 to 4 feet (0.9 to 1.2 meters) high. The blades measure from 6 to 12 inches (15 to 30 centimeters) long and about 1/2 inch (13 millimeters) wide. The plant is very leafy and has a loose, spreading flower cluster.
Sudan grass (Sorghum vulgare sudanense) makes good hay, pasture grass, and silage because it grows fast and can withstand dry weather. It has many fine stems and grows from 4 to 7 feet (1.2 to 2 meters) high. It has many narrow blades, and its flower clusters range from 6 to 18 inches (15 to 46 centimeters) long. Under certain conditions, sudan grass may prove toxic to livestock.
Timothy (Phleum pratense) is an important kind of grass used for hay. It grows from 20 to 40 inches (51 to 100 centimeters) high. It thrives in cool, humid weather. Its many stems make up large bunches of grass. Timothy flower clusters have a cylindrical shape.
Uses of Grass
Food

Most important of all grasses are the cerealsbarley, corn, millet, oats, rice, rye, grain sorghum, and wheat. Cereals are the major source of food for both man and animals. They grow in areas with temperate and tropical climates, produce good crops with a minimum of labor, and are easily harvested and stored. Ranking next is sugarcane, source of about half of the world's sugar.

Forage grasses are used both for pasture and for hay. They include such species as timothy, redtop, brome grass, Johnson grass, Bermuda grass, and Sudan grass.

Lawn and Garden

Kentucky bluegrass, bent grass, and redtop are the varieties most often sown for lawns. Bermuda, St. Augustine, and zoysia grasses are widely used in warm, humid areas. Crab grass, goose grass, and foxtail are some of the weed grasses that commonly infest lawns.

Ornamental grasses, such as hare's-tail and quaking grasses, are sometimes used in borders or for tropical effects.

GrassesGrasses can be used as ornamental ground cover or for forage.
Soil Conservation

Many grasses are used as green manure and cover crops. (A green manure crop is one that is grown, then plowed under to improve the soil. A cover crop is grown chiefly to prevent or reduce erosion.) Oats, rye, and ryegrass are commonly used as green manure; barley, oats, rye, and wheat as cover crops.

Other Uses

Grasses are used in making a wide variety of products, such as brooms, paper, cardboard, pressboard, cloth, hats, and garments. The bamboos are particularly important in southeastern Asia, where they are used as building material, in furniture, for water pipes, and for such utensils as bottles, cups, and pans. Grass is used for thatching roofs in some primitive areas. Citronella, a fragrant grass found in southeastern Asia, is the source of citronella oil, used in soaps, medicines, and perfumes. Holy grass, a sweet-scented grass native to Europe and North America, is often strewn in front of churches in northern Europe on saints' days.

Grasses belong to the grass family, Gramineae, of the order Graminales.