Rubia
(from ruber, red; alluding to the dye which is extracted from the plant). Madder. ORD. Rubiaceae. A genus comprising about thirty species of mostly hardy herbs, sometimes shrubby at the base, inhabiting mostly temperate regions. Flowers small or minute, in axillary and terminal cymes. Leaves in whorls of four or rarely six, very rarely opposite and stipuled, sessile or petiolate. The species are of no particular horticultural value. P. peregrina is a British evergreen. R. tinctorum is the species which furnishes the valuable dye.