bluegrass music: see country and western music.

bluegrass, any species of the large and widely distributed genus Poa, chiefly range and pasture grasses of economic importance in temperate and cool regions. In general, bluegrasses are perennial with fine-leaved foliage that is bluish green in some species. One of the best known and most important is the sod-forming Kentucky bluegrass, or June grass (P. pratensis), believed to have been introduced from the Old World and now widely naturalized in the United States; Kentucky is known as the Bluegrass State because this species is so prevalent there. Others are rough bluegrass (P. trivialis), used for shady lawns; Sandberg bluegrass (P. secunda), the most common native species; and big bluegrass (P. ampla), an important range grass. Bluegrass is classified in the division Magnoliophyta, class Liliopsida, order Cyperales, family Gramineae.

In music, a country-music style that emerged after World War II. It is a direct descendant of the string-band music played by groups such as the Carter Family. Bluegrass is distinguished from its predecessors by its more syncopated rhythm, its high-pitched tenor (lead) vocals, its tight harmonies, its driving rhythms, and a strong influence of jazz and blues. A very prominent place is given to the banjo, always played in the unique three-finger style developed by Earl Scruggs (see Lester Flatt). Mandolin and fiddle are generally featured, and traditional square-dance tunes, religious songs, and ballads furnish much of the repertory. Bluegrass was originated by and got its name from Bill Monroe and his Blue Grass Boys. From the late 1940s on, it continued to grow in popularity; from the 1970s an influx of younger musicians brought some influence from rock music.

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