Detailed Explanation of Longan Planting Techniques and Management Methods

Longan, also called guiyuan, is a precious specialty of southern China, rich in nutrients and valued as a tonic. The flesh contains 12.38-22.55% sugar, 3.85-10.16% reducing sugar, 9.59-13.59% invert sugar, 0.096-0.109% acid, and 43.12-163.70 mg of vitamin C per 100 g of flesh. It also contains vitamin K and inorganic salts. It has high medicinal value, with effects of tonifying the heart and spleen and nourishing the blood to calm the mind, and can treat weakness after illness, anemia and sallow complexion, neurasthenia, and blood deficiency after childbirth. Besides being eaten fresh, longan can also be dried, or processed into canned goods, longan paste, and more. Its seeds can be used to make wine.

Selecting Fine Varieties

Varieties in Fujian include Fuyan, Wuqiuben, Jiaoyan, Chike, Wulongling, Youtanben, Pumingyan, Dongbi, Jidan Longan, Honghezi, and others; varieties in Guangdong, Guangxi, Sichuan and other places include Shixia, Wuyuan, Caopuzhong, Zaohe, Daguangyan, Guangyan, Niukouzi, Luyuanqiang, Luyuan No. 6, Luyuan No. 106, Bayuexian, Fuling Huangke Longan, and others.

Longan Seedling Propagation

1. Seedlings

Choose a hillside plot sheltered from wind and frost, with good drainage and irrigation, deep soil, and a loose, fertile texture as the seedling bed. Plow to a depth of 20-33 cm, apply 5000 kg of turf soil, then plow and harrow and apply 2000-2500 kg of barnyard manure, then build beds 20—25 cm high and 1 m wide, with furrows 33-40 cm deep. The ratio of longan nursery to transplant nursery should be 1:6 or 1:7. Longan seeds must be sown immediately after collection. The extracted seeds should immediately be mixed with sand at a ratio of 1:2-3 and piled to germinate; the best germination temperature is 25℃, and the fine sand should have a moisture content of about 5%. When the embryo bud has elongated 0.5-1 cm, they can be sown in the seedbed. Broadcast sowing can be used, with a seed spacing of 8×10 cm and a sowing rate of 115—250 kg per mu; after sowing, cover with 2500-3000 kg of burnt soil or sand, then cover with rice straw, and then introduce water for irrigation and drain immediately after wetting. After emergence, management must be strengthened, such as watering and removing the rice straw. Fertilize to ensure vigorous growth of the seedlings. Transplant during the spring rainy season. When transplanting, prepare the land well and apply fertilizer well, with a spacing of 20×30-33 cm and 7000-8000 plants per mu. Manage promptly after transplanting.

2. Grafting Propagation

Use 5-6-year-old seedlings after field planting as rootstock, and graft by the inlay method. Select 2-year-old strong branches as scions, 1 cm thick and 4—12 cm long; the approach grafting method can also be used, with March to April being the best time, and tongue grafting and bud patch grafting can also be used for grafting propagation.

3. Air Layering Propagation

The method is to select, on strong plants over 15 years old, 3-4-year-old branches with a diameter of 3 cm and 2—3 side branches. Perform girdling 10-20 cm from the branch, about 40-50 cm wide, scrape off the bark, and when tumor-like tissue appears after 10-20 days, wrap with grass and mud, hang a pot and fill with soil, or wrap filler with plastic film as the rooting medium.

4. Cuttage

Take young longan shoots of the current year, cut them into 15-17 cm segments, and insert them into a hotbed at 27—29℃, shading and watering regularly. Before cuttage, first girdle the base of the selected branch, and after 1—2 days, apply 300 g of a mixed coating of 100 parts rice straw ash, 10 parts red mud, and 0.18 parts table salt, then wrap it, and after 2.5 months, cut it off from the mother branch for cuttage.

Longan Planting Techniques

Spring planting can be done in February to March, and winter planting can be done in late October. For planting density, a row spacing of 16 m and a plant spacing of 4.5 m can be used, with 19-20 trees planted per mu. For planting, first dig a planting hole 1 m deep, apply river mud at the bottom. Field soil and burnt soil, and apply decomposed compost, superphosphate and plant ash on top, all of which should be mixed with topsoil. After planting, sufficient irrigation must be given first, then cover with fine soil after irrigation, and thereafter irrigate 1-2 times daily. As for planting depth, the root crown should be level with the ground.

Shaping and Pruning

Use natural open-center shaping; in the 2nd-3rd year after planting, set the trunk at 1.2-1.3 m above the ground, and within 3-4 years cultivate 5-7 main branches, finally removing the central leader. Prune 3 times each year. The first pruning is at the flowering panicle stage, mainly cutting off diseased panicles, shaded branches and obstructing branches. The second is at fruit harvest, mainly cutting off short fruiting branches, water sprouts, diseased branches, dead branches and shaded branches. The third is in winter, mainly cutting off shaded branches, dead branches and diseased branches.

Fertilization

Apply base fertilizer once each year and topdress 3-4 times. The first topdressing is in February to March, applying night soil and ammonium sulfate, etc. The second topdressing is at the young fruit stage after flowers fade, about April to May, mainly applying nitrogen fertilizer, with appropriate phosphorus and potassium fertilizer. The third topdressing is from late June to early July, mainly phosphorus and potassium fertilizer, followed by nitrogen fertilizer. The fourth topdressing is when the fruit is nearly ripe, still mainly nitrogen fertilizer. The fertilization method is to open a ditch 30 cm from the trunk and apply into it. During fertilization, cultivation, weeding, earthing up, and drainage and irrigation can be carried out together.