Hylocereus undatus (dragon fruit)

The name Hylocereus undatus (Haw.) Britton & Rose was originally published in Britton’s Flora of Bermuda in 1918 (Britton, 1918). H. undatus is a climbing vine cactus species of the family Cactaceae. It is one of 15 accepted Hylocereus species native to Central and South America (while many of these species have ornamental value because of their flowers, only five are important as fruit producers).

The names of numerous genera in the Cactaceae end with the suffix ‘cereus’ as the genus Cereus was one of the first cactus genera to be described. Its name is derived from the Greek word keros or Latin cereus meaning 'wax taper', referring to the columnar habit of species in the genus. The name Hylocereus was subsequently given to the genus of similar cacti growing in woodlands, the prefix deriving from the Greek word hyle meaning a wood or forest. The specific epithet undatus is from the Latin for wavy, referring to the margins of the ribs of the plant’s stem (Eggli and Newton, 2004).

Common names such as 'dragon fruit', 'pitaya' and 'pitahaya' are generic terms which include several species of columnar and climbing cacti belonging to the Cactaceae family; they are is often applied to species other than H. undatus, and usually refer to the fruits rather than the plant.

The dragon fruit or pitahaya, Hylocereus undatus (Haworth) Britton & Rose (Cactaceae), is the second most important commercial cactus species with respect to fruit production after Opuntia ficus-indica. It is a hemiepiphyte (a plant that can grow anchored on trees or directly in soil) with a vine-like climbing tendency; its exact native range is uncertain, but believed to be in tropical regions of Mexico and Central America. The fruits, which have many names, have a delicate texture and delicious taste. They are extremely attractive visually. The flesh has high nutritional value, including high contents of vitamin C, calcium, potassium and fibre. Fruits have red or yellow peels and red as well as white pulp; the seeds are small and digestible. The plants are often trained onto trellises or arbours, similar to those used for grapevines, or a few plants may be associated with a post about 2 m tall with arms at the top from which the vines drape, allowing the fruit to develop at a convenient height for picking. Orchards can become profitable about 4 years after planting stem cuttings of about 40 cm in length. Fruit can be harvested from 25 to 45 days after flowering. The storage life is about 14 days at 10°C. The popularity of dragon fruit as an exotic fresh fruit has been increasing, particularly in non-traditional markets and where large Asian populations are established. Dragon fruit has potential as a health food due to its high levels of vitamin C, polyphenols and antioxidants.

Principal sources:  Janick and Paull (2008)

Hylocereus undatus is a vine-like cactus that is often grown as a night-flowering ornamental plant and as a fruit crop. The fruit is highly decorative, with a bright red skin, studded with green scales. The flesh is white, juicy and delicious in flavour, with tiny black seeds. Its exact native range is uncertain but is considered to be in Central America. Since the late twentieth century it has been widely planted on a commercial scale as a fruit crop in many tropical regions, particularly in Vietnam and other South-East Asian countries, and has escaped widely from cultivation, become naturalized and in many instances become an invasive weed, sometimes threatening native plants and habitats. Currently it is listed as invasive in China, Australia, South Africa, Cuba, and on many islands in the Pacific Ocean (Oviedo Prieto et al., 2012; PIER, 2016; Queensland Government, 2016).

Hylocereus undatus is a fast growing, epiphytic or xerophytic, vine-like cactus. Stems are triangular, 3-sided, although sometimes 4- or 5-sided, green, fleshy, jointed, many branched. Each stem segment has 3 flat wavy ribs and corneous margins may be spineless or have 1-3 small spines. Stems scandent, creeping, sprawling or clambering, up to 10 m long. Aerial roots, which are able to absorb water, are produced on the underside of stems and provide anchorage for stems on vertical surfaces. Flowers are 25-30 cm long, 15-17 cm wide, nocturnal, scented and hermaphroditic; however, some cultivars are self-compatible. Flowers are typically white in colour and bell shaped, stamens and lobed stigmas are cream coloured. Fruit is a fleshy berry, oblong to ovoid, up to 6-12 cm long, 4-9 cm thick, red with large bracteoles, pulp white, edible, embedded with many small black seeds. Average fruit weight is 350-400 g, although may weigh up to 900 g (Merten, 2002). 

In Vietnam and many other cultivation regions, fruit flies are a major pest and can prevent the export of fruit to many countries. Oriental fruit fly (Bactrocera dorsalis) and guava fruit fly (Bactrocera correcta) are species that both lay eggs in dragon fruit and the larvae can develop successfully even when the fruits are too green to eat (Lo and Waddell, 2001). This means that the fruits must undergo postharvest disinfestations before they can be exported to fruit fly-free countries for distribution and sale. Hot water disinfestation treatments are typically used, although they have the potential to damage the fruit and reduce shelf life.

The main insect pests reported are the stem-borer beetle Cotinus mutabilis; the sap sucker Leptoglossus zonatus (a chinch bug); the adult and larval forms of Metamasius fabrei striatoforatus; cutting and black ants (Atta and Solenopsis spp.) that attack the flower; and Photinus scintillans, a sucking insect that causes flower drop. Fruit flies (Bactrocera spp.) and others have been reported to be hosted by dragon fruit. Nematodes such as Meloidogyne, Helicotylenchus, Pratylenchus and Radopholus have been reported in Colombia (Paull and Duarte, 2012).

Aphids may infest flowers or fruit in some regions and young plants can be vulnerable to slugs and snails under damp conditions. Rabbits, squirrels, possums and similar pests have been known to feed on the lower stems, and mice, rats and birds will eat ripe fruit. Pest damage can be prevented with the use of wire screens around the base of the plant. Gophers may also create extensive damage if not kept under control (Merten, 2002).

The most important diseases affecting dragon fruit are anthracnose caused by Colletotrichum gloeosporioides [Glomerella cingulata]; basal rot caused by Fusarium oxysporum; ‘fish-eye disease’ caused by Dothiorella species; and stem necrotic lesions caused by Curvularia lunata [Cochliobolus lunatus]. Bacteria such as Erwinia carotovora can cause moist stem necrosis with a strong odour and Xanthomonas campestris can cause stem rot. Some viral diseases can also attack the plants. The use of clean planting material, clean tools, preventive and timely sprays, and elimination and burning of damaged material helps (Paull and Duarte, 2012). Viruses like Cactus virus X (CVX) have been reported on dragon fruit, causing symptoms such as stunted, malformed and mottled growth (Fudi-Allah et al., 1983). In Taiwan, CVX was found to be widespread in dragon fruit orchards, with infection rates of 60-90% in many regions (Liao et al., 2003). A strain of Fusicoccum has also been isolated from dragon fruit stems (Valencia-Botin et al., 2005).

Physiological disorders of dragon fruit include bleaching of the stems under high light which is exacerbated by water stress. Blistering and blackening of the stems can also result from extremes of temperature, poor fertility, over irrigation and other stresses.

The native range of Hylocereus undatus is uncertain, mainly because it has been widely commercialized and cultivated across tropical regions of the world. Currently, it is considered native to southern Mexico, the Pacific coast of Guatemala, Costa Rica, and El Salvador (IUCN, 2016). It is now commercially cultivated and widely distributed throughout the tropics and some temperate regions, including South-East Asia, China, Israel, Africa, Australia, North America, tropical South America and the West Indies (see Distribution table for details).

In pre-Columbian times, Hylocereus undatus became widespread in many tropical regions of the Americas and the Caribbean through dispersal by birds and by people propagating and cultivating the species for its edible fruits. It was first introduced into the Philippines by the Spanish in the sixteenth century; in China it was first introduced in 1645 (Flora of China, 2015); and it was introduced into Indochina by the French in the 19th century (around 1860). It later became an important fruit crop throughout South-East Asia and is now cultivated widely in the tropics and subtropics (Ortiz-Hernández, 1999; Nerd et al., 2002b; Nobel, 2002). 

In many situations where it has been planted it has escaped from cultivation to become a weed and in some regions an invasive.

In South Africa, where H. undatus, which was originally introduced as an ornamental, it has category 2 invasive status, i.e., it can be grown in gardens but only with a permit (which is granted under very few circumstances). Infestations, which tend to be limited and localized, and originate mainly from escapes from homestead gardens, impact native plant communities and the local ecology (Walters et al., 2011; Invasive Species South Africa, 2015).

In Brazil, it was introduced as a garden plant and sometimes escaped into roadside areas and maritime scrub, occurring in 11 states (Taylor and Zappi, 2004; Flora do Brasil, 2019).

In Hawaii, H. undatus was introduced in 1830 apparently in a shipment from Mexico of plants bound for China; most of the plants were being discarded because they were dead, but as the H. undatus plants were still alive they were planted out. They flourished and the species was soon commonly cultivated throughout the islands as an ornamental (Morton, 1987). Nowadays, H. undatus is regarded as invasive on the islands of Hawaii, Kahoolawe, Kauai, Lanai, Maui, Molokai, Niihau and Oahu (Wagner et al., 1999). Naturalized populations are well established in leeward areas of Oahu and Kauai (Staples and Herbst, 2005).

In Florida, USA, H. undatus has become a weed of disturbed areas in the south and centre of the state. Although the earliest specimen was vouchered in 1962, the species was probably introduced much earlier. In the Florida Keys it is classed as a category II invasive (increasing in abundance but has not yet altered plant communities by displacing native species). Manual removal is the only control method mentioned (Hadden et al., 2005).

H. undatus is becoming widely naturalized in eastern Australia where it is regarded as an environmental weed of open woodlands, dry rainforest, riparian areas and coastal vegetation in the warmer areas. It has been recorded in south-eastern and central Queensland and in the coastal districts of northern New South Wales; it appears on local weed lists in Byron Shire in northern New South Wales and Redland Shire in south-eastern Queensland. It is usually found growing on trees as a climber or epiphyte, and can even climb up into the canopy of very tall trees where it can form massive colonies; the weight of its succulent stems can eventually bring trees down (Queensland Government, 2011).

H. undatus is cited as invasive in numerous other regions throughout the world, including: Isla Más a Tierra (Robinson Crusoe Island) off the coast of Chile (Rachel Atkinson and John Sawyer, pers. observation, 2011); Cuba (Oviedo Prieto et al., 2012); the island of Île Grand Terre in New Caledonia (MacKee, 1994); the island of Niue (Space et al., 2004); and Réunion in the Indian Ocean (Lavergne, 2006). It has been found naturalized on the Canary Islands (Global Compendium of Weeds, 2015), as well as in Andalusia in mainland Spain (Dana et al., 2005).

The risk of introduction of Hylocerus undatus is high, mainly because it continues to be introduced as a commercial fruit crop. For example, it was recently (1997) introduced to Sri Lanka for this reason (Gunasena et al., 2007). Wherever it is grown as a fruit crop or ornamental there is the likelihood of escape from cultivation, either through seed dispersal by birds or, because of its ability to reproduce vegetatively, through distribution or disposal of plant material. On Niue, for example, H. undatus infestations were observed mainly along roadsides, apparently planted for ornamental purposes or resulting from the dumping of viable plant material (Space et al., 2004).

H. undatus is one of many alien species in Florida threatening the endangered plant species Chromolaena frustrata, Consolea corallicola and Harrisia aboriginum (US Fish and Wildlife Service, 2013).

Hylocereus ocamponis (Salm-Dyck) Britton & Rose is a similar cactus to H. undatus and is cultivated in Guatemala, Colombia, Bolivia and Puerto Rico. It has more deeply undulate wings bordered with brown and longer spines. The fruit is wine-red outside and inside, and the flesh is sweet (Morton, 1987). Other dragon-fruit-type Hylocereus species producing sweet fruits include H. costaricensis (red skin, red flesh) and H. megalanthus (yellow skin, white flesh).

Other climbing cactus species grown for their edible fruit include H. lemairei, producing fruits with red skin and red flesh dotted with edible black seeds, and Selenicereus megalanthus, the pitaya amarillo or yellow pitaya, producing fruits with yellow skin and clear to white flesh containing edible black seeds (Luders and McMahon, 2006).

Hylocereus undatus is a lithophyte or hemi-epiphyte tolerant of shade and, due to crassulacean acid metabolism, resistant to drought (Andrade et al., 2007a). It grows primarily in tropical dry forests and lowland tropical deciduous forest. Naturalized populations are found in tropical deciduous forest, tropical semideciduous forest, riparian vegetation, coastal forests, thorn scrub, and thorn forest (Arias Montes et al., 1997; Pérez-García et al., 2001). It is also found in disturbed areas, rocky areas, roadsides and maritime scrub (Taylor and Zappi, 2004; Flora of China Editorial Committee, 2015). In Mexico it has been found in highly heterogeneous environments, ranging from 2 to 2750 m above sea level, with annual rainfall ranging from 340 to 3500 mm and annual mean temperature ranging from 13° to 29°C (Cálix de Dios, 2004). In eastern Australia it can be found invading open woodlands, dry rainforest, riparian areas and coastal vegetation in the warmer areas (Queensland Government, 2011). In South Africa it can be found particularly in mesic, low-lying areas of KwaZulu-Natal, but also Mpumalanga and the Eastern Cape.

In Vietnam and many other dragon fruit cultivation regions, fruit flies are a major pest affecting fruit quality. Oriental fruit fly (Bactrocera dorsalis) and guava fruit fly (B. correcta) are species that both lay eggs in fruits and the larvae can develop successfully even when the fruits are too green to eat (Lo and Waddell, 2001). Hylocereus undatus is also a host for Anastrepha and Ceratitis spp. fruit flies (Invasive.org, 2015). Aphids may infest flowers or fruits in some regions and young plants can be vulnerable to slugs and snails under damp conditions. Rabbits, squirrels, possums and similar pests have been known to feed on the lower stems and mice, rats and birds will eat ripe fruits (Merten, 2002). 

Few diseases are reported on H. undatus, although stem rot caused by Xanthomonas campestris and brown spots on fruits caused by Dothiorella occur in some production areas (Zee et al., 2004). Viruses such as Cactus virus X (CVX) have been reported on dragon fruit plants, causing symptoms such as stunted, malformed and mottled growth (Fudi-Allah et al., 1983). In Taiwan, CVX is widespread in dragon fruit orchards, with infection rates of 60-90% in many regions (Liao et al., 2003). A strain of Fusicoccum has been isolated from stems (Valencia-Botin et al., 2005), and H. undatus is also a host to a quarantine-significant rust, Aecidium sp., known from Mexico (Invasive.org, 2015).

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Cropping systems

In high radiation regions, such as in Israel, dragon fruits are produced under shading provided by net houses, which also assist in reducing temperatures (Raveh et al., 1993). Dragon fruit crops also require some form of support as they are considered to be a vine-type cactus and can weigh over 50 kg at maturity. There are many different types of trellis structure in use for dragon fruit crops. Asian countries often incorporate use of a large diameter vertical pipe which encloses the central stem to a height of 2 m. The plant is permitted to branch at the top and the stems hang down around the sides of the central pipe where fruit are produced. Other countries use a standard fruit trellis system of posts and wires set at different heights. Plants are grown up to the top wire with branches trained downwards supported by lower wires, this system allows for easy access to the plants for pruning and harvesting operations. Between row spacing varies but is usually at least 2 m to allow access by machinery. Within the trellised row, plant spacing is usually between 1.5 and 3 m between plants. Higher densities give a plantation which produces higher yields more rapidly; however, the plants are likely to become overcrowded much sooner and require regular pruning or thinning. Some growers in South-East Asia grow dragon fruit as a secondary crop on live betel palm (Zee et al., 2004), whereas others utilise single wooden or cement pillars.

Dragon fruit plantations have been established on a wide range of soil types; however, well drained sites are preferred as the plants are prone to rotting under waterlogged conditions. The crop thrives on soil high in organic matter or where compost and manure have been added.

Propagation

Dragon fruit are easily propagated from both seed and stem cuttings. Most commercial plantations use cuttings as the preferred method of propagation which ensures uniformity of planting stock and prevents the genetic variation that can occur from seed-grown plants.

Dragon fruit plants tend to produce a large number of side shoots which can be removed and used as cutting material. Cuttings are selected from healthy stems of well hardened growth and removed by slicing through the flesh creating an 8-12 cm section. Cuttings are best selected as soon as the segmentation of the stems has occurred (Andrade et al., 2007b). A slanted cut on the stem will improve root formation. The cut stem must then be allowed to dry and callus over for a few days before planting into a damp, coarse, free draining media. Hormone rooting powder or gels can also be applied to speed up the rate of root formation. IBA has been shown to consistently improve rooting percentage, root number and root length (El-Obeidy, 2006). The optimal concentration of IBA for maximum rooting rate has been reported to be 500 mg IBA/L (Zhao et al., 2005). Propagation from cuttings is usually carried out in spring or summer or with use of heated greenhouse facilities in winter.

Production from seed is a much slower process. Cuttings will root within 2-3 weeks whereas seedlings can take up to 2 years longer than cuttings to begin fruit production due to the much longer juvenility period. The small black seeds are germinated by sowing into a fine, sterile growing medium such as vermiculite or potting mix and covered with plastic to maintain moisture. Warmth is required for rapid germination and propagation heat pads in greenhouse facilities are often used. Ideal germination temperatures range between 24 and 28°C (El-Obeidy, 2006). Germination usually occurs within 7-10 days under ideal conditions; however, young seedlings are slow to develop and require protected conditions for many months after germination has occurred.

Micropropagation of dragon fruit has also been examined as a way of rapidly bulking up new cultivars for commercial production. Explants are excised from young joints of mature plants and cultured on MS medium containing 0.5 µM naphthaleneacetic acid and 0.5 µM thidiazuron (Mohamed-Yasseen, 2002).

Planting

There are a number of named cultivars of dragon fruit with many of the newer, self compatible varieties originating from breeding programs in Vietnam and Asia. Many varieties have originated from seed although commercial plantations have also imported cuttings of selected cultivars from Asia and South America. Fruit quality varies between varieties as does the degree of self compatibility of the flowers.

Plantations are usually established from planting stock which originated as cuttings and have been grown on in a protected area for several months before planting out. Young plants need protection from excessive sunlight and regular irrigation to establish a well developed root system. Young plants should not be planted out until they have sufficient height to reach the trellis supports. Young plants need to be trained and pruned so that lateral stems are removed from the main stem which is tied to the trellis post. When plants reach the top of the trellis or support system the tips are cut back to induce branching and new laterals are then trained and tied to the trellis. If pruning is not carried out, the plant will naturally produce a dense mass of stems which restricts light and air penetration to the stems, makes spray penetration difficult and interferes with harvesting of the fruit. Unpruned plants are also more prone to pest and disease attack. Dragon fruit are vigorous plants and are often pruned several times a year to selectively remove some stems and train and tie remaining stems to the trellis framework.

Flowering, pollination and fruit development

Dragon fruit flowers in waves during the summer with three to four waves or flushes of flowers occurring each season. The flowering season is from May through to November in California, from June to October in Hawaii, and from June to October in Taiwan (Zee et al., 2004). During the flowering phase, three to five buds emerge from the stem tips, with two to three developing into flowers. The flower buds are typically large (20 cm in diameter) at the stage when anthesis occurs. Flower opening takes place in the early evening with flower petals closing again completely by dawn. Flowers may open earlier in the day in warm, low light conditions and later in the evening under cooler temperatures (Zee et al., 2004).

Flowers are pollinated by bats or moths; however, hand pollination is also used with self-incompatible varieties to ensure good fruit set and fruit size. This requires considerable labour input and many new commercial operations are utilising new cultivars which are self-fertile to avoid the cost of hand pollination. Many of the varieties bred in Asia are now self-compatible and will set fruit relatively easily without requiring hand pollination. The main disadvantage with many of the self-compatible varieties of dragon fruit is that the fruit is often smaller than if the flowers were cross-pollinated with pollen from a different clone or different species (Merten, 2002). This may be due to fruit weight which is positively corrected with the number of viable seeds and dependent on pollination. A number of studies have shown both fruit set and fruit weight have been shown to be lower with open pollination rather than hand pollination in dragon fruit (Weiss et al., 1994).

Hand pollination is carried out by removing the anthers from one flower and brushing them against the stigma of another or by collecting the pollen and using a small brush to pollinate many flowers. Commercial growers have to determine if it is worthwhile hand pollinating flowers in order to obtain a greater fruit weight, given the cost of labour and returns received for larger fruit. Often the first wave of flowers will not set fruit in self-incompatible varieties; however, a process has been developed for long-term storage of pollen which allows hand pollination whenever it is required. Pollen collected from dragon fruit flowers can be stored after drying to a moisture content of 5-10% and stored at below freezing temperatures. Pollen can be stored in this way for 9 months and used to pollinate the first blooms of the season resulting in an earlier and larger crop (Metz et al., 2000).

Commercial dragon fruit growers in Taiwan use supplemental night break lighting to increase the flowering period after the normal period of flowering has finished. Flowering is induced by breaking the dark period with lighting between 22:00 and 02:00 h, allowing off-season production from November to April (Zee et al., 2004). These fruit produced in the off-season often receive premium prices as they are larger and sweeter then those produced from summer crops. The recommended lighting uses incandescent light bulbs (100 W) at 4-5 foot spacings suspended 6 feet above the ground (Zee et al., 2004).

Growing conditions and husbandry

Dragon fruit, while being a type of cactus, perform poorly under extremes of temperature and cannot tolerate high light and temperature. Dragon fruit plantations must be sited in frost-free areas or incorporate some form of frost protection such as greenhouse production for cooler winter climates. Dragon fruit plants will show damage at temperatures of below 0°C and also above 40-45°C as they were originally adapted to shade canopy environments, and are not a desert species (Merten, 2002). In high radiation areas overhead shading is often installed which also helps reduce extremely high temperatures which can limit flowering and fruit set. High radiation levels cause the plants to become bleached in appearance caused by the destruction of chlorophyll in the stems, growth will also be retarded and plants may eventually die. However, under heavy shade the plants may become etiolated with reduced flowering and production levels. Recommendations for shading are to apply the minimal amount of shade required to prevent bleaching of the stems and ensure the plants are not water stressed as this reduces the crops resistance to high light damage.

Most high yielding commercial dragon fruit plantations use irrigation to maintain regular growth and prevent water stress. Dragon fruit have a shallow fibrous root system and require more water than a typical desert cacti having originated in areas with high levels of rainfall and humidity. The amount and frequency of irrigation is highly dependent on the soil type, climate and stage of crop development and has been reported to be an average of 5 L per plant per week in the summer season and 2.5 L per plant per week in the winter (Nerd et al., 1999). Careful irrigation management is required during the fruit formation stages as irregular watering and uneven soil moisture levels can result in fruit splitting.

Commercial growers may also use sprays of gibberellic acid and naphthalene acetic acid applied to fruit at approximately 11 days after flowering to increase fruit weight, total soluble solids and bract firmness (Van To et al., 2002). The growth regulator CPPU can be use to promote precocious flowering, and early fruit production (Khaimov and Mizrahi, 2006).

Nutrition

Little information exists on the fertilizer requirements of dragon fruit plantations although the crop does respond to small amounts of fertilizer which can be supplied via the irrigation system. Recommendations for fertilizer application state that 35 ppm of N supplied via the irrigation system is suitable and that care should be taken to avoid fertilizer burn of the shallow root system (Mizrahi and Nerd, 1999). Plantations in Taiwan have been reported to apply well decomposed cow manure at 9 pounds per plant every four months, supplemented with small amounts of commercial 13:13:13 fertilizer (Zee et al., 2004).

Harvest

Harvest timing has a considerable effect on final fruit quality as the soluble solids percentage increases from 5% on day 19 after flowering up to 16% or higher on day 43; indicating that a later harvest date will produce a better quality fruit. Consumers generally prefer dragon fruit with a total soluble solids/titratable acidity (TSS/TA) ratio of 40 and fruit for export should be harvested based on the TSS/TA ratio as this gives the best indication of flavour (Van To et al., 2002).

In Israel and Vietnam, the optimal time to harvest dragon fruit has been reported to be 28 to 30 days after flowering at full colour development (Nerd et al., 1999; Van To et al., 2002). However a longer developmental time is reported in California with harvesting recommended at 40-45 days post flowering. This typically corresponds to a Brix reading of 13-16% on average which corresponds to an acceptable level of sweetness for most consumers. Fruit which is harvested prematurely tends to be low in sugar and of poor quality, and be more prone to chilling injury, which will lead to a negative perception by those trying the fruit for the first time.

Fruit firmness decreases with maturity level in the period from 16 to 25 days after flowering. Soft fruit are difficult to handle and transport without damage; therefore fruit firmness should be taken into account when assessing harvest dates. Eating quality of the fruit flesh has shown to be most favoured by consumers when harvested at 28-43 days after flowering when sweetness levels are also highest.

Yield

Dragon fruit begin to produce economic yields within 2 to 3 years of planting, with full production reached in years 4 to 5. Vietnamese orchards are typically high yielding, possibly due to the selection of well bred cultivars, with many producing over 30 tons of fruit per hectare (Mizrahi et al., 1997). Plantings in Nicaragua have been reported to yield 10-12 tons per hectare in the fifth year of production (Jacobs, 1999). Commercial plantations may crop the same plants for up to 20 years before replacement with fresh stock. Plantations in Israel have reported yields of 28 -34 tonnes per hectare by year 5 (Nerd et al., 2002a).

(See Production and Trade section)

The fruit can be sold as ready to eat after peeling and/or slicing and put into microperforated polyethylene bags. Pulp can be frozen at -20°C and exported, although it is difficult to separate the seeds from the pulp. Dried slices can also be produced, but their water loss and shrinkage is great and prolonged exposure to heat affects the quality.

Fruit can be held at 6°C, although chilling injury can occur after 3 weeks and deterioration is rapid on return to room temperature. Modified-atmosphere packaging in polyethylene bags extends the fruit life to up to 35 days at 10°C.

Principal sources:  Janick and Paull (2008); Paull and Duarte (2012)

Dragon fruit have a chromosome number of 2n = 22 (Lichtenzveig et al., 2000). Hybrids have been produced between H. undatus and H. costaricensis to overcome self-incompatibility. Molecular markers that have been used to categorise Mexican and Colombian varieties showed 92.54% polymorphism among, within and between populations. The Colombian selection is related to most of the Mexican selections, suggesting a common origin (Paull and Duarte, 2012).

Recent breeding and selection in Taiwan and Vietnam has produced many self-fertile and productive dragon fruit varieties, including selections such as 'Vietnam No. 1' which produces large, pink fruits with white flesh and high levels of total soluble solids (Zee et al., 2004). One of the major problems with breeding of the self-compatible cultivars is that these still tend to produce smaller fruits than when cross pollination is carried out, and breeding work is aimed at solving this problem. Further breeding work to develop varieties that can withstand a wider range of climatic conditions, including frost and high temperatures, may be a future focus.

There are many types of red dragon fruit based on selections made by farmers according to a special characteristic of the plant, not necessarily yield or fruit quality. In Nicaragua, three varieties are asexually propagated for the export market: ‘Lisa,’ ‘Rosa’ and ‘Cebra’. These same varieties are produced in Costa Rica. In many cases different species are involved, often with natural crosses among or between them. The market distinguishes dragon fruit only by the colour of the fruit (yellow or red) and the flesh (white or red).

There are a number of named cultivars of dragon fruit, with many of the newer, self-compatible varieties originating from breeding programmes in Vietnam and Asia. Many varieties have originated from seed, although commercial plantations have also imported cuttings of selected cultivars from Asia and South America. Fruit quality varies between varieties, as does the degree of self-compatibility of the flowers.

Principal sources: Paull and Duarte (2012)

The fruits of H. undatus have a delicate texture and delicious taste. The edible pulp of yellow dragon fruit is sweeter because of a higher sugar content. Dragon fruit are extremely attractive visually and do not have the spines or the annoying glochids of cactus pears (Opuntia ficus-indica), and the much smaller seeds (similar in size and texture to those in kiwifruits) are readily swallowed. The fruits can be relatively large, often exceeding 500 g, with yellow or red peels and pulps varying from white to yellow to red to deep purple.

The flesh has high nutritional value, including high contents of vitamin C, calcium, potassium and fibre. The pH is generally 4-6. The red colour of the pulp is caused by betalains, natural pigments that replace anthocyanins and have high antiradical activity. Eating the fruits is claimed to reduce cholesterol, help the digestive system and prevent cancer.

Principal sources: Janick and Paull (2008), Paull and Duarte (2012)

History of cultivation

Dragon fruit is commonly cultivated throughout the tropical American lowlands (Zee et al., 2004) and has become a commercially important crop in many countries elsewhere. It has been cultivated in Vietnam for over 100 years, having been originally introduced to this region by the French, and initially it was grown exclusively for the king and royal family and later for wealthy families (Lo and Waddell, 2001). Vietnam until recently was the only country in Asia producing dragon fruits on a commercial scale, exporting to Hong Kong, Singapore, Malaysia, China, Taiwan, Japan and the EU. Main production areas in Vietnam are Binh Thuan, Lon An and Tien Giang provinces. Some 6000 ha in total are planted to the crop.  Total production in Vietnam is estimated to be 70,000 tonnes per year of which 15,000 tonnes is exported. In Mexico, another large dragon fruit producer, there are about 2000 ha planted to the crop, about half being in the Yucatan peninsula (Van To et al., 2002; Janick and Paull, 2008; Paull and Duarte, 2012).

Dragon fruit is also commercially produced on a limited scale in the Philippines, Malaysia, Taiwan, southern China, Nicaragua, Colombia, Israel, Australia and the USA. In 2002, it was reported that only 10-15 hectares of dragon fruit were planted commercially on the US mainland, all in southern California, with additional commercial plantings in Hawaii (Merten, 2002). Since 2002 dragon fruit plantations have been established in Florida. In total over 20 countries have established dragon fruit plantations to date (Nobel, 2006).

Postharvest handling

Dragon fruits are non-climateric and have a low rate of respiration when mature. Harvested fruits usually maintain acceptable quality for at least two weeks after harvest when stored at 14°C (Nerd et al., 1999). Fruits stored at room temperature typically only last 10 days, whereas those stored in perforated plastic bags at 5°C will maintain quality for as long as 25-30 days (Zee et al., 2004). High temperatures in summer tend to accelerate the ripening and senescence of dragon fruit and fruits harvested during this season benefit from pre-cooling and storage at low temperatures (Wu et al., 1997).

The main postharvest problems seen with dragon fruit are often due to harvesting pre-maturity and incorrect use of growth regulator sprays which leads to misshapen fruits with unacceptable colour and green spots (Van To et al., 2002). Some fruit will require postharvest disinfestation treatment for fruit fly before export is permitted to many countries. Methods of postharvest disinfestation include heat treatment to a core fruit temperature of 46.5°C for 20 minutes, which does not appear to affect the storage quality of the fruit (Hoa et al., 2006).

Shelf life of ripe dragon fruit can be extended with use of modified atmosphere packaging (MAP) using polyethylene bags with an oxygen transmission rate of 4 L/m²/hour at 10°C. (Van To et al., 2002). One study has reported that intermittent heating (4 weeks with 2 days at 20°C) during refrigeration reduced damage and increased shelf life up to 30 days (Gongora et al., 2004). Hydrothermic preconditioning has also been proven to prolong shelf life. Fruits placed in permeable plastic bags and immersed in water at 40°C for 3 minutes were shown to have reduced cold damage when stored at 8°C for 25 days (Camara et al., 2004).

Dragon fruit may be peeled before shipment to export markets, as this has been shown to not accelerate deterioration of the fruit, although slicing had a negative effect on keeping quality (Goldman et al., 2005).

The popularity of dragon fruit as an exotic fresh fruit has been increasing, particularly in non-traditional markets and where large Asian populations are established. However, imports of dragon fruit from some regions where fruit fly infestations are a problem may restrict production unless reliable disinfestation methods are used. Dragon fruit has potential as a health food due to its high levels of vitamin C, polyphenols and antioxidants, which have shown promise in the treatment of melanoma (Wu et al., 2006).