Selenicereus undatus, the white-fleshed pitahaya, is a species of the genus Selenicereus (formerly Hylocereus) in the family Cactaceae and is the most cultivated species in the genus. It is used both as an ornamental vine and as a fruit crop - the pitahaya or dragon fruit. Like all true cacti, the genus originates in the Americas, but the precise native origin of the species S. undatus is uncertain and never been resolved; it may be a hybrid. Description Plant Dragonfruit stems are scandent (climbing habit), creeping, sprawling or clambering, and branch profusely. There can be four to seven of them, between or longer, with joints from or longer, and thick; with generally three ribs; margins are corneous (horn-like) with age, and undulate. Areoles, that is, the small area bearing spines or hairs on a cactus, are across with internodes . Spines on the adult branches are long, being acicular (needle-like) to almost conical, and grayish brown to black in colour and spreading, with a deep green epidermis. Flowers The scented, nocturnal flowers are long, wide with the pericarpel long, about thick, bracteoles ovate, acute, to 2.5 to less than long; receptacle about thick, bracteoles are linear-lanceolate, long; outer tepals lanceolate-linear to linear, acuminate (tapering to a point), being long, wide and mucronate (ending in a short sharp point). Their colour is greenish-yellow or whitish, rarely rose-tinged; inner tepals are lanceolate (tapering to a point at the tip) to oblanceolate (i.e. more pointed at the base), up to long about wide at widest point, and mucronate, unbroken, sharp to acuminate (pointed), and white. Stamens long, are declinate, inserted in one continuous zone from throat to above the pericarpel and cream. The style (bearing the stigma) to 17, they are long, stout, thick, cream, and up to 26 stigma lobes, they can be whole or sometimes split at the top, cream, about long. Nectar chambers are long. Fruit The fruit is oblong to oval, long, thick, red with large bracteoles, with white, or more uncommonly, pink pulp and edible black seeds. Habitat Selenicereus undatus is lithophytic or hemiepiphytic. It is widely distributed through the tropics in cultivation. It is a sprawling or vining, terrestrial or epiphytic cactus. They climb by use of aerial roots and can reach a height of 10 meters (32.8 feet) or more growing on rocks and trees. Systematics This species is closely related to S. ocamponis and S.