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usually Cephalocereus senilis, a columnar species of cactus (family Cactaceae), native to central Mexico. Because of the wisps of whitish hair along its stem, it is a popular potted plant. It grows well outdoors in Mediterranean climates. C. senilis usually attains 6 metres (about 20 feet) before flowering and can grow to twice that height. Other attractive forms such as yellow old man, or woolly torch (C. palmeri), flower at about 60 cm (2 feet). The flat-faced flowers are produced from a mass of long wool and bristles that cap the stem or form a beard on one side of it, depending on the species. Flowers are night-blooming in C. senilis, pink outside and white within