Fruit Trees of Vietnam:

The Litchi Tree

The litchi belongs to the family Sapidacceae. Although it is not as important as banana and mango plants as far as crop acreage and output are concerned, they are considered as a specialty of Vietnam. They are highly appreciated in both domestic and foreign markets and will possibly become an important export in the form of fresh fruit when storage and transport methods are improved.

The edible part of the fruit is the fleshy section surrounding the seeds and protected by a skin covering. Litchi is a subtropical fruit most highly appreciated as it is grown only in northern Vietnam, southern China, and India and not on a large scale.

Litchi has male, female and bisexual flowers on the same raceme, however male and female flowers mature in different periods and xeongamic pollination is due to bees, small butterflies and several kinds of flies. Previously, there was propagation by seeding, but due to strong variation in gardens of commercial farming, vegetative propagation is done by aerial layering. In the litchi plantation of Phu Lam (Hai Duong), there are farmer families specializing in litchi aerial layering and in the sale of young plants.

Annual sales income of these young plants is higher than that for fruits. The litchi plant can be grafted, however the grafted tree has a low rate of survival and bears fruit late and this method is rarely applied in litchi production.

Several litchi varieties are suitable to hilly acid soil with a pH level of 5.0-5.5. They grow fairly well in old garden soil where litchi trees have been planted previously due to the favorable influence of mycorhizes. Alluvial and riverside soil are also good for cultivation at distances of 20 yards. In the north, litchi plantations require no watering or irrigation-when the tree needs water (particularly in March-May), it is often raining and there is no need to irrigate.

Litchi has no dangerous pests or diseases, however there is a species of brown bug that sucks the sap of young shoots and fruit, making the fruit fall.

In northern Vietnam, litchi ripens in May-June and the output is about 7-8 tons in a good crop year. Their transport is difficult-they have so much sugar and juice content that when they meet higher air temperatures, they soon rot.

The main difficulties are in appropriate methods of storage, rapid transport, good processing and conservation of the fruit's aroma. A good solution to these problems will give rapid growth to litchi farming.

The Mangosteen

Everyone is familiar with tropical fruit and in tasting it for the first time, one appreciates the aroma-with a proportionately sweet and sour taste. In markets where mangosteen is sold, the price is always ten times higher than that of other fruit.

It is an evergreen tree of beautiful appearance and provides much shade. The mangosteen garden Lai Thieu (close to Ho Chi Minh City) is a much appreciated holiday resort as the fruit are planted on high beds separated by small furrow drains. Water is routed up and down daily and creates a fresh shady microclimate for the fruit and anyone resting under the shade of the trees, especially at midday.

In Vietnam, there are five to six varieties of mangosteens cultivated or growing wild as "Bua." Bua fruit is edible but its quality is inferior to mangosteen. The pulp is used to cook sour soup and the seeds are used for oil pressing. There is no wild mangosteen growing in Vietnam, however it does grow wild in Malaysia and Indonesia.

Ecological growing requirements of mangosteen are strict: a microclimate under tropical rainforest that is humid but has no direct sunlight. There should be no strong, violent winds, especially when the tree is still young. When trees are growing, they shelter one another and require no other shade. They always need a fresh, humid environment, fertile soil, plenty of humus and good drainage. The most suitable temperature is 25-30 C. Because of the above requirements, mangosteen is cultivated only in the La Thieu area (Song Be province) and in some fields among the Mekong Delta where the soil is fertile and not contaminated by salt and where the water has easy drainage such as Ben Tre, Tien Giang and Hau Giang. In red soil area, there are only a few scattered trees growing in the valleys, out of the wind.

A unique phenomenon of this special fruit is that there is only one variety of mangosteen throughout the world. Scientists have hypothesized that the plant has pollen but is not capable of fertilizing ovaries. If a mangosteen has seeds, it is due to the nucleus that is stimulated and developed inside the seed. Therefore, the embryo is similar to the initial (mother) plant. This is a method of vegetative propagation so there is no variation.

Breeding, however, can be done by seeding. Seedlings are similar to the mother plant, but have unusual variations. Mangosteen seed has a very thin skin and loses its germination capacity rapidly and so it must be sown immediately.

Like sapodilla, young mangosteens develop very slowly. Because the root bundle is very weak, it is necessary to intensify cultivation. Fertilizers, weeding and pest and disease controls are necessary and eventually, the trees must be sheltered from both wind and sunlight. Even with these precautions in Lai Thieu, the young plant bears fruit late-from 8-10 years of age, it begins to bear fruit and from the age of 15-20 years, it has an output which begins to make a profit. Mangosteen trees live for over 100 years in spite of the damage of a few pests and diseases. In Lai Thieu, there are thousands of trees that are over 100 years old.

Efforts are made to drive root cuttings into the ground and to graft tree shoots onto other plants of the guttiferae family in the hopes that the newly grafted trees will bear flowers and fruit early.

Harvesting is done when the mangosteen turns from white to red but never when it is deep purple. The fruit can be stored up to seven days; when it is stored longer, the pericarp will oxidize and become hard and the pulp will be rotten to the core.

The Durian

In addition to Vietnam, the southeast Asian specialty, durian, is also grown in Malaysia, India and Thailand. In southern Vietnam, it is the most precious and expensive fruit due to its small quantity of pulp in comparison with the total weight of the fruit. Only gourmets can completely appreciate the qualities of this kind of fruit: sweet, fattened, soft and with a very special aroma. People unfamiliar with durian are often afraid of its strong smell.

Durian is native to rainy tropical forests close to the equator in southeast Asia. Like the mangosteen tree, it requires growth conditions with humidity, fresh foliage, and gentle winds particularly when the plants are young. The durian tree tolerates low temperatures therefore it can be planted in highland areas such a Di Linh and Duc Trong in Lam Dong province at an altitude of 3000-4000 feet. Cultivated low-lying durian is easily infected by root disease. Therefore in Nam Bo (in the south), the crop acreage of durian is narrow and plantation is concentrated in red soil regions. In the Mekong Delta, beds of durian gardens must be higher, however the plant dies easily due to fungal diseases. The durian is completely unsuitable for cultivation in the north due to the cold winter and high humidity.

Due to propagation by seeding and xenogamy, the quality of durian is not homogeneous. There are good durian trees where the ratio of the edible portion of their fruit is about 30-40% with excellent quality. And then there are also durian plants with small fruits where the ratio of edible portion is only 10-15%. Therefore good trees must be chosen and vegetative propagation must be carried out to expand production.

Durian seeds are big and rapidly lose their germination capacity. Seeds taken from the fruit must be sown immediately. For splice grafting, seed will be sown in polyethylene bags containing 1000 grams of soil; a young plant of 3-4 months of age can be bound to the mother plant or grafted onto a middle-aged branch.

Young durian develops slowly with weak roots and dies easily when too many mineral fertilizers are put close to the foot of the tree. The plant will be dwarfish when it is cultivated in a windy place and in strong sunlight. Therefore, from the beginning, young plants should be nursed in polyethylene bags and in a covered place with weak illumination of 30-40%, constant moisture and intensive manuring with a small quantity of fertilizers each time. The fixed planting of durian trees must be done at the beginning of the rainy season and planted at 30 x 30 yards under shaded trees.

To prevent root disease, it is necessary to choose a slight slope, well drained with deep soil and without stones or clay close to the surface of the earth. It is very difficult to determine harvesting time by the color of the fruit. The best way is to wait for the durian to fall down. Due to its rather long thorns that protect its outside, the fruit is rarely bruised. Durian fruit should be processed into foodstuff products that are easily sold in the market.

Source: destinationvietnam.com