3. Opuntia monacantha Haworth, Suppl. Pl. Succ. 81. 1819.
单刺仙人掌 dan ci xian ren zhang
Cactus monacanthos Willdenow, Enum. Pl. Suppl. 33. 1814; C. indicus Roxburgh.
Shrubs or treelike, 1.3-4 m tall. Trunk (when present) terete. Larger, terminal joints glossy green, obovate, narrowly so, obovate-oblong, oblong, or oblanceolate, 10-30 × 7.5-12.5 cm, thin, narrowed basally, margin undulate toward apex. Areoles 3-5 mm in diam. Spines sparse on joint 1 or 2(or 3) per areole, but on main trunk to 12 per areole, erect or spreading, grayish, dark brown tipped, acicular, 1-7.5 cm; glochids brownish, 2-3 mm. Leaves conic, 2-4 mm, deciduous. Flowers 5-7.5 cm in diam. Sepaloids with red midrib and yellow margin, obovate or broadly ovate, 0.8-2.5 × 0.8-1.5 cm, apex rounded or emarginate. Petaloids spreading, yellow to orange, or obovate to oblong-obovate, 2.3-4 × 1.2-3 cm, margin subentire, apex rounded, truncate, or muricate. Filaments greenish, ca. 12 mm; anthers pale yellow, ca. 1 mm. Style greenish, 1.2-2 cm; stigmas 6-10, cream, 4.5-6 mm. Fruit reddish purple, obovoid, 5-7.5 × 4-5 cm, umbilicus slightly depressed. Seeds light tan, irregularly elliptic, ca. 4 × 3 mm. Fl. Apr-Aug.
Seashores, slopes; sea level to 2000 m. Fujian, Guangdong, Guangxi, Taiwan, Yunnan [native to Argentina, Brazil, Paraguay, and Uruguay; widely introduced and naturalized in tropical and subtropical regions].
This species was first recorded in China in 1625.
When describing Opuntia monacantha, Haworth based the name on a plant from Barbados, where only O. dillenii is currently recorded as native. Haworth’s name has now been neotypified to maintain its use in the sense employed here and is the earliest name consistently applied to this widely introduced plant, which is native to SE South America. Haworth cited Cactus monacanthos Willdenow 1814 in synonymy with a "?," but this indication of doubt rules out Willdenow’s untypifiable name as a potential basionym for that of Haworth. An earlier name formerly and widely applied to O. monacantha is O. vulgaris Miller. This confused name has now been typified to become a synonym of O. ficus-indica (Linnaeus) Miller (see Leuenberger, Taxon 42: 419-429).