Longan looks like lychee, is much sweeter and yields twice as much as the best lychee tree. Its fruit is smaller than lychee, and has brown smooth skin and therefore is called “Little Brother of Lychee”.
It is very popular in South-East Asia where from large quantities are exported to Europe and so why shouldn’t Pakistan take advantage? Logan is new to Pakistan. There are a few trees at the Ayub Agriculture Research Institute at Faisalabad, but some six new varieties are at my farm, being grown there for past eight years. The first commercial crop was sold in 2003.
The 2004 crop brought excellent prices of Rs50 per kg at the Karachi Sabzi Mandi Market against Rs100 for early lychee harvested in last fortnight of May, due to its being very early in the whole South-Asia.
It can be grown in Sindh possibly up to Rahim Yar Khan as per climatic data available. May be it can be extended up to Khanpur but not further.
The climatic requirements are that young trees are killed at -1C and frosts being common above Sadiqabad, losses during the first three years will be heavy. Mature plants can be killed at -4øC and so once established there is little chance of their being killed.
It flowers after 200 hours of chill and flowers early in January in the Punjab but its flowers are also killed at 0øC, and freezes do occur at end of January and early February and therefore it does not fruit there. One favourable factor for southern Sindh is the resistant of tree to normal summer wind velocities sometimes reaching 40km daily, but most of time these are below 30km i.e., from April 15 to September 15.
However, cyclone winds can cause splitting of branches, fruit drop and even tree loss, especially in morcotts with small shallow roots. Wind breaks, therefore, will be essential in lower Sindh from Sakrand-Nawabshah down south to the coast.
They need full sunlight for maximum yield and fruit does not show sun burns or sun scald. Cloudy weather leads to 50 per cent reduction in yield. Since flowering is spread to 6-8 weeks, bad weather i.e., winter rains which cause flower drop, spare at least half of crop even in bad years. It does not stand drought and weekly irrigation in summer, 10-day interval in autumn and spring, and 15-day in winter is essential. Its moisture requirement is same as of sugarcane and lychee, about 80 inches in Sindh, more than that of mango which needs about 65-70 inches.
Fruiting in Sindh is from mid-July to mid August. In the rainy season, over-cast weather prior to harvest causes fruit drop. However rainfall occurs only on average of seven days in July-August in Sindh and so the losses are limited. Problem is severe in areas north of Rahim Yar Khan.
Its chill requirements are lower than lychee and needs only 2-3 months of temperatures less than 15-22øC. Even mild coastal areas of Sindh have temperatures lower than this from December to February. Low temperatures less than 10øC for eight weeks or more produce no flowering which is the main hurdle in its expansion in Punjab. As Sindh have low temperatures than needed for flowering, such temperature produce higher percentage of female flowers in longan and therefore a better crop and high yield.
Soils of irrigated areas of Sindh and Punjab are suitable for this crop, except that high water table is counter-productive and therefore in rice area it is grown on mounds of about 0.5m high along the tree rows. Excess water can kill the trees. It can tolerate medium saline soils and second class ground water which lychee and mango do not.
Fruits are smaller than lychee about 1.5 to 3cm in diameter, globes to round in shape. It is less acidic than lychee has more sugar and mild flavour. Its Brix content can reach 22 to 240. Its seeds are similar to lychee but as they do not belong to same species. All attempts to bud and graft each others rootstocks have failed.
Propagation by seed is possible, but it would yield first crop after seven to eight years and commercial crop two years later, where as marcotts yield in year three and commercial crop in year four, but success of morcotts is low at about 15-20 per cent. Grafts are successful but only on own rootstock.
Propagation by grafting is successful, but all attempts to graft except approach grafting have failed in Pakistan due to lack of experience among the nurserymen. These factors have come in the way of large-scale propagation in South-Asia though it is common fruit tree in many countries.
Different varieties have different sized trees. Dwarf varieties can be planted to about 218 trees per acre. Moderate density is 174 plants per acre against low density of 70 plants. Its fertiliser requirement are also low and half as much as mango, lychee or citrus. Fruiting age is 2-4 years for asexual, 2-3 years for marcotts, 3-4 years for grafts and 7-8 years for seedlings.
A yield of 10 tons/acre is possible, though in Thailand it is six tons per acre in year nine: High yield can make tree biennial and we remove 50 per cent flowers in the “on year”. The net result is 75 per cent crop each year. This can hit 10 tons/acre in year 12-13.
Yield per tree varies with management and it varies between 70-110kg for medium management and 135-225kg for well managed orchards in Florida. Under good management yield in Pakistan can be 15-30kg in year five. Some varieties can produce 75kg in year six. In general yield can be 10kg per tree, per year life as a thumb rule.
For export to any place in the world after post-harvest treatment, it can be kept for 30-90 days. It can be used as fresh fruit for table use or dried in 20 days and moisture reduced by 66 per cent. Dried longan is considered highly delicious. Even seeds are used as shampoo as they contain shampnish. It can be canned and is superior to canned lychee. It can easily be frozen in airtight containers and on thawing it can be used as freshly picked fruit during the season.
For export hydrocooled at 5øC and stored, it can last for 40-45 days and at 10øC for 20 days, but relative humidity of 85-90 per cent is needed. At ambient temperature of 25-31øC in August in Karachi, its life will be 4-5 days. For export, of 15-20 gram size is preferred against 21-24 grams for lychee. Preference between lychee and longan is the acquired taste. Thailand produces more fruit than China and 12-15 tithes more than lychee due to local demand. For, marketing bunches with two leaves attached to stem and 300-500 grains punnets are also used.
In term of nutrition, it has 18-24 per cent sugar, in edible portion of 66-78 per cent, seed and skin accounting for the rest. It is rich in vitamins A, B1, B2, Niacin and C with iron as mineral. It has more calories i.e., 4.58 kilo calories against four of sugar. As leaves contain quercetin and quercetrin, they are used in medicines, flowers as herbs and seeds for shampoos: In brief it has very high economic potential.
