II.

Importance

All the world’s cereal crops are grasses, and thus the grass family is economically very important. The world’s 5 top crops produce more tonnage than the next 25 combined, and 4 of the top 5 are the cereals rice, wheat, corn, and barley. Human well-being depends on these few grasses, so even small crop failures of any one of them can produce widespread hunger and economic disruption. In addition, the family provides most of the world’s sugar (see Sugarcane). Another member of the family, bamboo, is an important construction material as well as a food source; it also has been used in papermaking. Citronella, used both in perfumery and as an insect repellent, is an oil distilled from the leaves of certain grasses.

Grasses are the primary source of food for domestic and wild grazing animals, which feed on pastures and grasslands and which are fed hay and silage harvested from them. The total land area devoted to these kinds of croplands is greater than the land area for all other kinds of croplands combined.

Another economically significant use of grasses is for the lawns maintained in many parts of the world. Perennial grasses are well adapted for use in lawns because their basal meristems (growing points) are not lost with mowing. Widely grown in the northern United States are Kentucky bluegrass (actually a native of Europe), bent grasses, and fescue. Bermuda grass and zoysia are better adapted to the warm conditions of the southern states. Often special grasses are used where particular conditions of soil or exposure make the more common species unsuitable. For example, buffalo grass is used where watering is restricted, as in the Great Plains region, and carpet grass may be used on poorly drained soils. Occasionally, annual grasses such as redtop are used to establish a lawn in a short time, but they often persist, compete with the perennial grasses, and become unsightly.

In fact, not all grasses are beneficial, and some are considered pests. Most of these are weeds that occur in croplands and decrease overall production by competing with the cultivated crop, interfere with harvesting, or lower the overall food or other value of the crop by contamination. Some tropical forage grasses produce lethal concentrations of hydrocyanic acid under certain conditions.