A pitaya (pron.: //) or pitahaya (//) is the fruit of several cactus species. "Pitaya" usually refers to fruit of the genus Stenocereus, while "Pitahaya" or "Dragonfruit" always refers to fruit of the genus Hylocereus.
Vernacular names of Hylocereus 
These fruits are commonly known as "dragon fruit" as in the Cambodian language Sror Kaa Neark--"dragon scale", in the Chinese huǒ lóng guǒ, "fire dragon fruit", and lóng zhū guǒ, "dragon pearl fruit". The Vietnamese thanh long meaning "green dragon", the Malay buah naga, the Lao mark mang gohn, and the Thai kaeo mangkon or "dragon crystal". Other vernacular names are strawberry pear or nanettika fruit.
The vine-like epiphytic pitahaya-producing cacti of the genus Hylocereus are native to Mexico, Central America, and South America. Currently, they are also cultivated in East Asian and Southeast Asian countries such as Cambodia, Thailand, Taiwan, Malaysia, Vietnam, Sri Lanka, the Philippines, Indonesia and more recentlyBangladesh. They are also found in Okinawa, Hawaii, Israel, northern Australia, southern China and in Cyprus.
The fruit was probably introduced by Europeans who brought it from the New World. In the case of Taiwan, the fruit was brought in by the Dutch.
Hylocereus blooms only at night; the large white fragrant flowers of the typical cactus flower shape are among those called "moonflower" or "Queen of the Night". Sweet pitahayas have a creamy pulp and a delicate aroma. It is also grown as an Ornamental plant, used in gardens as a flowering vine and a house plant indoors.
Pitaya varieties 
Stenocereus fruit (sour pitayas) are a variety that is commonly eaten in the arid regions of the Americas. They are more sour and refreshing, with juicier flesh and a stronger taste. The sour pitaya or pitaya agria (S. gummosus) in the Sonoran Desert has been an important food source for Native Americans. The Seri people of northwestern Mexico still harvest the fruit, and call the plant ziix is ccapxl – "thing whose fruit is sour". The fruit of related species, such as S. queretaroensis and the dagger cactus (S. griseus), are also locally important food. The Organ Pipe Cactus (S. thurberi) fruit (called ool by the Seris) is the pitaya dulce ("sweet pitaya"). It still has a more tart aroma than Hylocereus fruit, described as somewhat reminiscent of watermelon; it has some uses in folk medicine.
Fruits of some other columnar cacti (mainly Cereeae) are also called "pitayas" – for example those of the Peruvian Apple Cactus (Cereus repandus), which are very rare.
Pitahaya varieties 
Sweet pitahayas come in three types, all with leathery, slightly leafy skin:
- Hylocereus undatus (Pitahaya blanca or White-fleshed Pitahaya) has red-skinned fruit with white flesh. This is the most commonly seen "dragon fruit".
- Hylocereus costaricensis (Pitahaya roja or Red-fleshed Pitahaya, also known as Hylocereus polyrhizus) has red-skinned fruit with red flesh.
- Hylocereus megalanthus (Pitahaya 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 latter is probably the red pitahaya.
The fruit can weigh from 150 to 600 grams; some may reach one kilogram.
After thorough cleaning of the seeds from the pulp of the fruit, the seeds may be stored when dried. Ideally, the fruit must be unblemished and overripe. Seeds grow well in a compost or potting soil mix - even as a potted indoor plant. Pitahaya cacti usually germinate between 11 and 14 days after shallow planting. As they are cacti, overwatering is a concern for home growers. As their growth continues, these climbing plants will find something to climb on, which can involve putting aerial roots down from the branches in addition to the basal roots. Once the plant reaches a mature 10 pounds in weight, the plant may flower.[clarification needed]
Pitahaya flowers bloom overnight and usually wilt by the morning. They rely on nocturnal pollinators such as bats or moths for fertilization. Self-fertilization will not produce fruit in some species, and while cross-breeding has resulted in several "Self-Fertile" varieties, cross-pollinating with a second plant species generally increases fruit set and quality. This limits the capability of home growers to produce the fruit. However, the plants can flower between three and six times in a year depending on growing conditions. Like other cacti, if a healthy piece of the stem is broken off, it may take root in soil and become its own plant.
The plants can handle temperatures up to 40 °C (104 °F) and very short periods of frost, but will not survive long exposure to freezing temperatures. The cacti thrive most in USDA zones 10-11, but may survive outdoors in zone 9a or 9b.
Hylocereus has adapted to live in dry tropical climates with a moderate amount of rain. The dragon fruit sets on the cactus-like trees 30–50 days after flowering and can sometimes have 5-6 cycles of harvests per year. There are some farms in Vietnam that produce 30 tons of fruit per hectare every year.
Pests and diseases 
Overwatering or excessive rainfall can cause the flowers to drop and fruit to rot. Also, extended over-watering can cause maturing fruit to split on the branch. Birds can be a nuisance. The bacterium Xanthomonas campestris causes the stems to rot. Dothiorella fungi can cause brown spots on the fruit, but this is not common.
To prepare a pitaya for consumption, the fruit is cut open to expose the flesh. The fruit's texture is sometimes likened to that of the kiwifruit because of its black, crunchy seeds. The flesh, which is eaten raw, is mildly sweet and low in calories. The seeds are eaten together with the flesh, have a nutty taste and are rich in lipids, but they are indigestible unless chewed. The fruit is also converted into juice or wine, or used to flavour other beverages. The flowers can be eaten or steeped as tea. The skin is not eaten, and in farm-grown fruit it may be polluted with pesticides.
Ingestion of significant amounts of red-fleshed dragon fruit (such as Costa Rican Pitahaya) may result in a harmless reddish coloration of the urine (pseudohematuria) and of the faeces.
Several of the Padres who missionized Baja California recorded an unusual form of consumption of pitaya that is also shared in some O'odham stories from southern Arizona. It is called the "second harvest" of pitaya seeds. With the scarcity of fruits in their lands, the pitaya was such a prized fruit that once it was eaten, the natives would wait for their own excrement to dry, then break it apart separating the pitaya seeds. These seeds would be ground into a flour and eaten again, giving the pitaya's "second harvest" its name. Interestingly, the O'odham name for the Milky Way translates as "the second harvest of pitaya."
The mild taste of pitahaya flesh is often remarked upon, as it stands in stark contrast to the vibrant exterior. The taste has been described as being "very bland... like a melon or kiwi," with a "mild sweetness."
Nutritional information 
The edible parts of raw pitahaya consist of mostly water and carbohydrates, with some protein and fat content. Pitayas contain slight amounts ofcalcium, iron, phosphorus, and other nutrients.
The fatty acid compositions of two pitaya seed oils were determined as follows:
|Hylocereus polyrhizus (Red-fleshed pitahaya)||Hylocereus undatus (White-fleshed pitahaya)|
- Particularly red-skinned pitayas are a good source of vitamin C.
- Pitayas are rich in fiber and minerals, notably phosphorus and calcium. Red pitayas seem to be richer in the former, yellow ones in the latter.
- The seeds are rich in polyunsaturated fatty acids, and in particular Red Pitayas contain very little saturated fat.
- Pitahayas also contain significant quantities of phytoalbumin antioxidants
- In Taiwan, diabetics use the fruit as a food substitute for rice and as a source of dietary fiber.