|Fruit of Hylocereus undatus|
(Haworth) Britton & Rose
Hylocereus undatus (White-fleshed Pitahaya) is a species of 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 Dragonfruit. The native origin of the species has never been resolved.
Common names 
- English: Pitahaya, Dragonfruit, Night blooming Cereus, Strawberry Pear, Belle of the Night, Conderella Plant
- Estonian: maasik-metskaktus
- French: fruit du dragon, cierge-lézard, poire de chardon
- German: Drachenfrucht, Distelbirne
- Hawaiian: panini-o-ka-puna-hou ("Punahou cactus") - a famous specimen still grows at Punahou School
- Portuguese: pitaia, cato-barse, cardo-ananaz, rainha da noite
- Spanish: pitahaya blanca (Colombia, Mexico, Venezuela); flor de caliz, pitajava (Puerto Rico); junco, junco tapatio, pitahaya orejona, reina de la noche, tasajo (Mexico)
- Swedish: skogskaktus, röd pitahaya
- Vietnamese: thanh long
- Thai: แก้วมังกร (kaeo mangkon)
- Malay: buah naga. pronounce:boo-ah naa-gaa
- Chinese: 火龙果 （huǒlóngguǒ）
H. undatus is named for its undulate or wavy margins of the ribs.
In 1836, Mrs. Bingham planted the hedge of Hylocereus undatus, the famed cactus known in Hawaii as panini o kapunahou. Its exotic blossoms still bloom during the closing summer months on the Punahou walls. The hedge is on two sides of the school and about three hundred meters long.
From July to as late as October the hedge blooms and several times there is a wall of white flowers hundreds of yards long. Supposedly all the H. undatus in Hawaii came from the wall of Punahou School. People used to come in the evenings from all over the island to see them blooming and "borrow" some cuttings so that now they have this species all over the islands.
Origin and habitat 
Lithophytic or hemiepiphytic. Widely distributed through the tropics in cultivation, it originates in Makassar, Indonesia
This species is closely related to H. ocamponis and H. escuintlensis.
An easily cultivated, fast growing epiphyte or xerophyte. Needs a compost containing plenty of humus and sufficient moisture in summer. Should not be kept under 10°C (50°F) in winter. Can be grown in semi-shade or full sun. Extra light in the early spring will stimulate budding. Flowers in summer or autumn.
Stems scandent, creeping, sprawling or clambering, branching profusely, 4-7,5 (-10) m long or more, joints to 30–120 cm long or more, 10–12 cm thick; ribs generally 3; margins corneous in age, undulate; areoles 2 mm in diameter; internodes 1–4 cm; spines on adult branches 1-3, 2–4 mm long, acicular to subconic, grayish brown to black, spreading; epidermis deep green. Flowers 25–30 cm long, 15–17 cm wide, nocturnal, scented; pericarpel 2,5–5 cm long, ca 2,5 cm thick, bracteoles ovate, acute, to 2,5 (-4 ) cm long; receptacle ca 3 cm thick, bracteoles linear-lanceolate, 3–8 cm long; outer tepals lanceolate-linear to linear, acuminate, 10–15 cm long, 10–15 mm wide mucronate, greenish yellow or whitish, rarely tinged rose; inner tepals lanceolate to oblanceolate, to 10–15 cm long ca 40 mm wide at widest point, mucronate, entire, acute to acuminate, white; stamens 5–10 cm long, declinate, inserted in one continuous zone from throat to 35 mm above pericarpel, cream; style to 17,5-24.5 cm long, stout, 6–8 mm thick, cream, stigma lobes to 26, entire or sometimes cleft at apex, cream, ca 25 mm long. Nectar chambers 30 mm long. Fruit oblong to ovoid, to 6–12 cm long, 4–9 cm thick, red with large bracteoles, pulp white, edible; seeds black.
Dragonfruit cost about £1-2 each in the UK, PHP 90/kg in Indang, Philippines. In Taiwan they are about 45 NT each, and depending on season, can be found in Hong Kong for 10 HKD for 3 (3.33HKD/per).
See also 
- Staples, G.W. & Herbst, D.R. 2005. A tropical garden flora. Bishop Museum Press,Honolulu. 908 pp
- Donald Fitzgerald, 1991. Pearl Harbor, the Army Corps of Engineers, and Punahou's Cereus Hedge., The Hawaiian Journal of History, vol. 25
- Anderson, E. F. 2001. The cactus family. Timber Press, Portland, Oregon, USA.
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