Dragon fruit

Dragon fruit, also called pitahaya or pitaya, is the fruit of several species in the cactus genus Selenicereus, particularly Selenicereus undatus.

Dragon fruit is native to the southern regions of Mexico and the Pacific coast of Guatemala, Costa Rica, and El Salvador. In the 21st century, its cultivation has expanded to regions including Vietnam, China, Colombia, and Southeast Asia.

For fruit of the genus Stenocereus, see Pitaya (Stenocereus). For other uses, see Pitahaya (disambiguation).

Description

The dragon fruit is a tough, juicy cactus that is drought resistant. It has long, triangular stems and often twists around nearby trees, taking moisture from their bark. It can climb 8 to 10 metres (26 to 33 ft) without growing into the ground. Its flower is tube-shaped and bisexual. It opens only once at night, and its smell attracts insects. The flower is self-pollinating, but it can also be pollinated by other plants, and bats are a natural pollinator.

The fruit grows from pollination to harvest in 4 to 8 weeks, depending on the temperature. It is oval-shaped, about 10 by 6 centimetres (3.9 by 2.4 in). Before it ripens, the inside is green. It later turns yellow or red, depending on the variety. The pulp contains small black seeds. The skin is covered with bright red or yellow, fleshy, ovate scales. The red and purple colours of some Selenicereus fruits come from betacyanins, a group of pigments that includes betanin. Betanin is also what gives beets, Swiss chard and amaranth their red colour.

Species

Dragon fruit mainly comes in three types. Selenicereus undatus has pink skin and white flesh, and it is the most commonly seen kind. Selenicereus costaricensis has red skin and red flesh. Selenicereus megalanthus has yellow skin and white flesh, and it is often called "yellow dragon fruit."

Each fruit weighs about 150 to 600 grams, and some can reach 1 kilogram. Early imports from Colombia to Australia were named Hylocereus ocampensis (or Cereus repandus, the red fruit) and Cereus triangularis, which was thought to be the yellow fruit.

Cultivation

Seeds are cleaned from the pulp and dried, and the best fruit is unblemished and overripe. The seeds grow in compost or potting soil mix, including in pots indoors. The cacti sprout 11 to 14 days after shallow planting, and they find something to climb on as they grow. Once a plant reaches 4.5 kilograms (10 pounds), it may flower. Commercial plantings use 1,100 to 1,350 plants per hectare (445 to 546 per acre). A plant can take up to 60 months (260 weeks) to reach full commercial production, and yields of 20 to 30 metric tons (22 to 33 short tons) can be expected.

Dragon fruit flowers bloom overnight and usually wilt by evening. They rely on nocturnal pollinators such as bats or moths. Some species cannot make fruit by pollinating themselves, and cross-pollinating with a different plant of the same species usually improves fruit set and quality. The plants can flower three to six times a year. They can survive up to 40 °C (104 °F) and short frosts, but not long freezing. They grow best in USDA zones 10–11 and may survive outdoors in zone 9a or 9b. The plants have adapted to dry tropical areas, and in many places they have escaped cultivation and become a weed, classed as an invasive weed in some countries. Large amounts are grown in Vietnam, China, Mexico, Colombia, Southeast Asia, and Australia, where Vietnam grows Selenicereus undatus.

Stems and fruits can be harmed by diseases caused by fungi, bacteria, nematodes, and viruses. Too much water can make flowers drop and fruit rot. One bacterium, Xanthomonas campestris, causes stems to rot, and Dothiorella fungi can cause brown spots on fruit. Other fungi that infect fruit include Botryosphaeria dothidea, Colletotrichum gloeosporioides, and Bipolaris cactivora.

Nutrition

Raw dragon fruit is mostly water, about 84%, and about 15% of it is carbohydrates. It has very little protein and fat. A 100-gram (3.5 oz) serving gives 57 kilocalories (240 kilojoules) of food energy. It does not contain large amounts of any micronutrients.

Culinary

When cut in half, a raw dragon fruit can be eaten with a spoon. Its juice can flavor and color drinks, pastries, or candy. The flowers can be eaten as a vegetable or steeped as a tea.

Seed oils

The seed oils of Selenicereus costaricensis, also known as Hylocereus costaricensis (red-fleshed pitaya), and Selenicereus undatus, also known as Hylocereus undatus (white-fleshed pitaya), have similar fats. These include palmitic acid, stearic acid, palmitoleic acid, and mainly oleic acid (22%) and linoleic acid (50%).