Origin and distribution
Native to Guangdong, Guangxi, Yunnan and other provinces (autonomous regions) and northern Vietnam. According to the records of Sanfu Huang Tu and Qunfangpu, China has a cultivation history of at least 2,000 years. The cultivation history of Sichuan is about 2000 years, and 1600 years ago was introduced to Fujian. At present, Fujian has the largest longan cultivation area and output, followed by Taiwan Province, Guangdong and Guangxi, and Sichuan, Yunnan and Guizhou have less output. Longan planting countries in the world are mainly distributed in South Asia. Besides China, there are Thailand, India, Viet Nam, the Philippines and other countries. However, some tropical and subtropical areas in America, Africa and Oceania were gradually introduced after 19 century, and most of them were in the stage of introduction and trial planting.
Features and characteristics
Longan is a long-lived fruit tree with a normal fruiting period of nearly a hundred years. The height of the tree is 6 ~ 10 meter. The crown is almost round. The root system is deep and wide, the vertical root is buried 2 ~ 3 meters deep, the horizontal root spread is 1 ~ 3 times larger than the crown, and the absorbed roots are mostly concentrated in the soil layer above 40 ~ 50 cm. With mycorrhiza, mycorrhiza is bigger than absorption root, and there is no root hair. The trunk is thick and the epidermis is longitudinally cracked. Strong branch top advantage, few branches, firm quality, hard and brittle. Most of the leaves are even pinnate compound leaves, with 3-6 pairs of leaflets, opposite or alternate, mostly rectangular, all leathery, 10-20 cm long and 3-6 cm wide. The leaf surface is green, the back is light green and the veins are obvious. Inflorescence is a cyme, a mixed inflorescence arranged conically, with hundreds to two or three thousand flowers. The flowers are small and dense, yellow and white, hairy and slightly fragrant, mainly male and female, but also a few bisexual and deformed flowers. The fruit is drupe-shaped, oblate or spherical, and the single fruit weight is 10 ~ 15g. The peel is yellowish brown, thin and smooth, the edible part is aril, milky white or pale white, and the meat is crisp and sweet. The seeds are round to oblate, dark black or reddish brown, smooth and shiny (see figure).
The annual cycle of root growth has 3 ~ 4 peaks, and the growth of new roots and shoots alternates with each other. It is hot and humid from June to August, and the root system grows the most. Shoot 3 ~ 4 times a year, that is, spring and autumn 1 time and summer 1 ~ 2 times (sometimes 3 times in summer). Most of the new buds come out from the terminal buds of complete branches, and some are drawn from short branches or adventitious buds. Longan belongs to the type of flowering and fruiting in the year of flower bud differentiation. Flower buds differentiate in February-April and bloom in April-May. The flowering period of a single plant is about 30-45 days, and the male and female flowers in a single flower cluster alternate or alternate. The fruit setting rate is about 10 ~ 20% of that of female flowers. Fruit drop of longan is the first physiological fruit drop from 3 to 20 days after pollination, and the second physiological fruit drop from mid-June to mid-July, and it is less until maturity. There are three growth peaks in fruit growth, and the fastest growth is in the middle and late period (after early July). The general maturity period is from August to September.
Longan likes temperature, the average annual temperature is 20 ~ 22℃, and it is not suitable for cultivation in areas with absolute low temperature below -5℃ in winter. Flower bud differentiation needs a period of relatively low temperature, and the average temperature in Leng Yue is about 65438 02℃, which is relatively drought-tolerant. The annual rainfall in the subtropical region of South China can usually meet the needs of its growth and fruiting, but it often leads to flowers and fruits falling in flowering and young fruit, so it should be drained in time. Pay attention to typhoon prevention during fruit ripening. Longan has strong adaptability to soil, but loam with deep soil layer and pH value of 4.5 ~ 6.5 is the best.
principal item
China is rich in longan variety resources, among which Fujian Province is the largest, followed by Taiwan Province Province, Guangdong and Guangxi. The most cultivated variety in Fujian is ① Yanfu. This variety has strong adaptability, high yield, large fruit, thin skin and medium quality, and is suitable for canning, fresh eating and baking. ② Wulongling. It is an important main cultivated variety in Fujian, with high yield, large fruit, high sugar content, medium quality and high baking rate. ③ East wall. It is a famous rare and fine variety with high yield, big fruit, thick meat, crisp quality, sweet flavor, high sugar content and good quality. It is an excellent fresh food. In addition, Red Shell, Shuizhang, Youtangben, Puming 'an, Buron, Habitat, Banana Eye, Red Kernel are also important varieties in Fujian. The most important variety in Guangdong is Shijie, with high yield, medium-sized fruit, thin skin, high sugar content, thick and crisp meat and excellent quality, which is suitable for fresh eating and drying. The more important varieties are crisp meat, black circle, Shuang Mu, big eye, grass seed, autumn wind seed, top circle and big circle. The main varieties in Taiwan Province Province are Qilinkeng Zaosheng, Round Pink Shell, Black Pink Shell, Pineapple Flavor, October Longan, Baiba Zaosheng, Lombok and Niulan. The main varieties in Guangxi are Dayuyuan, Xiadui Longan, Rock Sugar Meat, Yan Guang and Bobai Longan. Due to the long-term use of seedlings in various places, there are still many excellent types or strains.
Key points of cultivation techniques
The main breeding methods are high-pressure strip and grafting. Fujian has a long history of high-pressure transmission. Seedling has the characteristics of pure variety, fast growth and early fruiting, but its propagation coefficient is low. Grafting methods mainly include high tongue grafting, cutting grafting and butt grafting, and the grafting survival rate is high. In recent years, seedling grafting methods such as bud grafting and long branch abdominal grafting have been widely used in various places, with good results and can improve the propagation coefficient of seedlings.
Longan orchard should be south, and horizontal terraces should be built in hilly and mountainous areas, with row spacing of 5 ~ 8 meters. Generally, it is planted in spring and autumn, and it is suitable to plant in spring in areas with serious frost damage. Young orchards can be interplanted with fast-growing short-term fruit trees, leguminous crops or other cash crops. The suitable height of young tree trunk is 60 ~ 100 cm: 3 ~ 4 branches with vigorous growth and uniform distribution are selected as main branches to cultivate a circular crown. Fertilize adult trees five times a year: before heading; After ear thinning to before flowering; After fruit thinning; Rapid expansion stage of pulp; After picking the fruit. Generally, the fertilization amount is 50 ~ 100 kg per fruit, and pure nitrogen (N) 1 ~ 2 kg, phosphorus (P2O5) 0.5 ~ 1 kg and potassium (K2O) 1 ~ 1.5 kg are applied throughout the year. Adult orchards are ploughed shallowly 3-4 times a year, ploughed in August-September and 65438+10-February, and deeply ploughed after picking fruits, with about 0.5 tons of soil for each plant. When there is drought in summer and autumn, water the fruit trees to increase the yield and promote the germination of autumn shoots. Pruning of adult trees should be carried out in spring, summer and autumn to remove over-dense, over-weak, insect pests and disorderly branches based on the principle of keeping the trees strong and cultivating excellent fruiting mother branches.
Longan bears fruit in different years. For plants with many flowers and fruits, some ears and fruits should be thinned in a timely and appropriate manner to promote a certain number of robust summer shoots to sprout as the mother branches of flowers and fruits in the next year. The suitable thinning time is 12 ~ 15 cm, and the first and middle days of April are suitable in Fujian. The thinning amount of ear is about 50 ~ 70%, and the thinning principle is: "leave less at the top of the tree, more at the lower layer, less at the periphery and more at the inner side." Remove the dragon and leave the vice (the dragon is the leading ear, which is the flower ear protruding from the top of the outer branch of the crown; The attachment is the second strongest side spike), which is left after folding. " At the same time, the diseased ear, weak ear and flowering ear with poor leaf development should be thinned out. The remaining nails must be evenly distributed. Fruit thinning is mostly carried out in June, with dense fruit, mixed fruit, diseased fruit and deformed fruit.
The main pests of longan are stinkbug litchi, Lepidoptera, leaf roller moth, peach moth, Lychee grey butterfly and other fruit moths. Witches' broom disease is the main dangerous disease, which has great influence on production, followed by leaf spot disease, coal disease, fruit rot disease and root disease.
economic value
Longan is a famous specialty fruit in the south subtropical zone of China. The sugar content of pulp is as high as 12 ~ 23%, and the contents of vitamin C and vitamin K are also high. Every100g of pulp contains vitamin C43.1~163.7mg, and vitamin K196.5mg. Dried longan can not only be eaten fresh, but also be roasted, which has the effects of nourishing the heart, strengthening the spleen, nourishing blood and calming the nerves. It is welcomed by consumers at home and abroad and is an important export commodity, which sells well in Southeast Asia. Fruits can also be processed into canned sugar water and longan sauce. Stone contains high starch content and can be used for wine making. Wood is hard, durable and fine-grained, and it is a high-grade material.