” A pitaya /pɪˈtaɪ.ə/ or pitahaya /ˌpɪtəˈhaɪ.ə/ is the fruit of several cactus species indigenous to the Americas. Pitaya usually refers to the fruit of the genus Stenocereus, while pitahaya or dragon fruit refers to the fruit of the genus Hylocereus. These fruits are commonly known in English as “dragon fruit”, reflecting its vernacular Asian names. The names pitahaya and pitaya derives from Mexico, and pitaya Roja in Central America and northern South America, possibly relating to pitahaya for names of tall cacti species with flowering fruit. In China, the fruit is referred to as huǒ lóng guǒ.
Dragon fruit Hylocereus
Ripe dragon fruit, Vietnam
Sweet pitahayas come in three types, all with leathery, slightly leafy skin:
- Hylocereus undatus (Pitaya Blanca or white-fleshed pitahaya) has pink-skinned fruit with white flesh. This is the most commonly seen “dragon fruit”.
- Hylocereus costaricensis (Pitaya Roja or red-fleshed pitahaya, also known as Hylocereus polyrhizus) has red-skinned fruit with red flesh.
- Hylocereus megalanthus (Pitaya Amarilla or yellow pitahaya, also known as Selenicereus megalanthus) has yellow-skinned fruit with white flesh.
Early imports from Colombia to Australia were designated Hylocereus ocampensis (supposedly red fruit) and Cereus triangularis (supposedly yellow fruit). It is not quite certain to which species these taxa refer, though the former is probably the red pitaya.
The fruit normally weighs from 150 to 600 grams (5.3 to 21.2 oz); some may reach 1 kilogram (2.2 lb).” https://en.wikipedia.org/wiki/Pitaya