Rubia(redirected from Rubiá)
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(madder), a genus of plants of the family Rubiaceae. They are perennial grasses, subshrubs, or low shrubs. The leaves are simple and decussate, with interpetiolate stipules that resemble leaves. The small flowers are in axillary or terminal cymes, which are frequently gathered in paniculate or, less frequently, racemose inflorescences. There are about 55 species in the temperate zones of Asia and the Mediterranean region. A few species are found in Central Europe and in Africa, and about 15 species are encountered in Central and South America. There are 20 species in the USSR, primarily in Middle Asia. The underground organs of certain species yield dyes. Madder (Rubia tinctorum) has been cultivated since antiquity for its bright and durable color, which, depending on its processing, can dye fabrics red, violet, orange, canary yellow, or other colors. Since the discovery in the 1860’s of synthetic alizarin, madder has been cultivated only in a few Asian countries, where it is used to dye carpets.