Scientific: Hylocereus undatus (Haw) Brit. & Rose
English: Dragon fruit
Thai: Kaeo Mangkon, Luk Mangkon
Vietnam: (Cay) Thanh Long
4.5.2 General: The fruits, having very attractive color and shape similar to the eyes of the imaginary animal, the dragon, have been quite popular in Vietnam under the name of ‘dragon’s eyes’ or ‘thanh long’. In addition to its attractive color and shape, the dragon fruits also have a high nutritional value including vitamin C, calcium, potassium and fiber. They are claimed to reduce cholesterol that is the cause of coronary heart disease. As it helps the digestive system and also prevents cancer, the fruit is considered by some as a health fruit. Until recently, Vietnam was the only country in Asia producing dragon fruits on a commercial scale, exporting to Hong Kong, Singapore, Malaysia, China, Taiwan, Japan and EU. Main production areas in Vietnam are: Binh Thuan, Lon An, Tien Giang.
4.5.3 Origin and distribution: Originating in Central America, the dragon fruit plants were brought to Vietnam about 50 years ago. It is commonly cultivated in Vietnam and a few other countries like Southern China and recently in Thailand, Australia and Taiwan.
4.5.4 Description: A plant belonging to the cactus family, resembles other cactus in being three sided, winged with a fragmented viny stem (similar to the fin of the dragon). The plant climbs on any type of support - other trees, walls, a trellis etc.. At each node, there is no leaf (like the other cactus plants), but instead, a group of 4 to 5 spines attached to the stem. The fruit is egg-shaped about 7 to 10 cm wide, 10 to 15 cm long and weighs 300 to 700 g. The skin is leathery, thin (2 to 3 cm), brilliant reddish color with several greenish, soft flat scales protruding out towards the end of the fruit. The flesh is pure white, soft, juicy with numerous small black seeds. Both the flesh and seeds are edible with a pleasant mild sweet/sour taste and characteristic aroma making it pleasant to eat especially during hot weather.
4.5.5 Ecology: Although dragon fruit grows in any soil types and is quite drought resistant, it prefers well-drained soils with pH of 6.3 to 6.8 and soils high in organic matter. It needs bright sunshine. Rainfall should not be more than 2500 mm per year.
4.5.6 Genetics and improvement: Other species of Hylocereus include: H. polyrhizus, H. costariciensis and another unidentified species, all of which produce edible fruits but smaller in size that H. undatus.
4.5.7 Major cultivars in Vietnam: Two cultivars, namely Binh Thuan and Cho Gao, are commonly grown in Vietnam. SOFRI has successfully bred the red-fleshed cultivar with the local ones, resulting in some outstanding clones of red-fleshed dragon fruit. It is expected this red-fleshed cultivar will be released for production within two years.
4.5.8 Propagation: Dragon-fruit plant can be propagated by seed but the most practical method is by cutting. The stem to be used for propagation should be more than one-year old. A cut stem section of 20 cm is inserted in the propagating medium - sand, burned rice husk, or potting soil. Rooting hormone is not necessary as the cutting develops roots easily in about 30 to 45 days and is ready for transplanting.
4.5.9 Planting: To obtain optimal yield and quality, the dragon plant should be grown in fertile soil with irrigation.. A trellis can be constructed in the following manner. Take a 2.5 m long cement post and embed one end 0.5m in the soil. On the top of the post, attach a wooden crosspiece to support the vines of the plant. Normally, four plants are grown at each post, one on each side of the post. Dig each hole for the plant 30 x 30 x 30cm add manure and compost to the soil and plant. Spacing between is 3 x 3 m. In lowland areas, good drainage should be provided during the rainy season since the root system of the dragon plant is susceptible to waterlogging. During the first year, water regularly (about once every five to seven days) but take care not to over-water. Control weeds and apply mulch. Chemical fertilizer at a rate of 15-15-15, 1 kg/post (of four plants), should be split into six applications, during the first year. In years 2 to 3, more manure and/or compost, and fertilizer (15-15-15, 8-24-24, or 19-20-26) should also be applied in order to provide enough nutrient for the growing dragon plants.
4.5.10 Pests and diseases: Dragon-fruit plants do not seem to be susceptible to pests and diseases. Only minor pests are encountered - aphid (Pentalonia nigronervosa), mealy bug (Pseducoccus brevipes) and ants (Solenopsis geminata, Iriidomyrmex humilis and Pheidole megacephala) which can be easily controlled by common insecticides. Collar rot (Phytopthora sp.) and root rots (Fusarium sp., Alternara sp.) are the two main diseases, which can be controlled by fungicides. Weeds are normally controlled manually, and the residue is to be left to cover the hole as mulch.
4.5.11 Fruiting season: Dragon fruit plants produce fruits almost all year round, especially if irrigation and fertilizer are provided. Timing of fruit ripening to satisfy the market demand at particular period can be done by providing additional light during the short-day period to induce flowering at the required period.
4.5.12 Harvesting and yield: Harvesting is done by manually picking each mature fruit. Dragon plant is a high yielder, with a yield of 50 to 80 t/ha, provided good cultural practices are adopted.
4.5.13 Post-harvest operations: Being a delicate fruit, care must be taken in handling the transport of fruits from the farm to the market. Special care is provided in the packing for the export market, where special cartons are used. The fruits keep well in the refrigerator, and in fact, the quality improves after storage. If consumed right after picking, the fruit is a little sour, but sweetens after keeping a few days.
4.5.14 Problems: The fruit is not well known in other countries so the export market is limited. At present, there is an improvement program to develop new cultivars of the dragon fruit as well as an international project for pest and disease identification on this crop. However, the existing dragon fruit cultivars are good, having high quality and accepted by the cosummers; thus this is not a major constraint..
4.5.15 Prospects: Having attractive color and shape, supplemented with high nutritional value and pleasant taste and aroma, dragon fruits have great potential as export commodity to countries like China. At present Vietnam exports dragon fruits to several nearby countries particularly Hong Kong and Singapore. It has great potential to be exported to European markets as its taste is liked by Europeans. It has less sugar content than most popular tropical fruits, and thus is more suitable to diabetics and high blood pressure patients. In very near future, the red-fleshed cultivars having high sweetness, hight vitamin A and self polination of flowering, will be released.