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.[1]
Like all true cacti, the genus originates in the Americas,S. undatus is originates from Mexico to Honduras;[2] it may be a hybrid. It is most frequently attributed to the island of Martinique in the West Indies[3]
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.[1]
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.[1]
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; These outer tepals, or sepals are about 65 in number, and bring the flower to a total width of up to fourteen inches (35 centimeters).[4] 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.[1]
The fruit is oblong to oval, long, thick, red with large bracteoles, with white, or more uncommonly, pink pulp and edible black seeds.[1]
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.
This species is closely related to S. ocamponis and S. escuintlensis. Selenicereus undatus was described by (Haw.) Britton & Rose and published in Flora of Bermuda 256. 1918. In 2017, D. R. Hunt groups the genus Hylocereus within the genus Selenicereus. This has been supported by a phylogenetic analysis of the Hylocereeae tribe (Korotkova, et al., 2017), therefore this species is consigned under the name Selenicereus undatus[5]
The species's epithet undatus in Latin means "wavy" from unda "wave",[6] referring to the wavy edges of its branches' ribs.