On this page:

• Soils and climate
• Windbreaks
• Cultivars
• Propagation and land preparation
• Fertilising
• Pruning
• Harvesting and post-harvest storage
• Economics and market

Soils and climate

Mangosteen is a lowland humid tropical forest tree. An equatorial climate, a high even temperature with high humidity, is ideal. A temperature range from 20°C to 33°C is desirable. The northern Queensland environment is suitable for mangosteen production. However, the cool temperatures experienced during the July/August months in northern Queensland will limit the areas where mangosteen can be grown. They can only be grown at elevations below 500 m.

Temperatures below 5°C will kill mangosteen trees, especially juvenile trees, and growth is significantly reduced below 20°C. Leaves become scorched at temperatures above 35°C, but older trees seem to be more tolerant to extremes in temperature. Providing abundant soil moisture is available, the above ground conditions do not significantly impact on mangosteen growth. Irrigation is essential during the dry season.

Mangosteen will grow on a wide range of soils provided it has good water holding capacity. However, it will not tolerate waterlogged areas. Trees can recover from temporary waterlogging and prefer a high water table, 1.5-2 m below the surface. A slightly acid soil in the range of pH 5 to 6 with moderate clay content and a high amount of organic matter is preferable (e.g. a heavy clay alluvial loam). Liming is not recommended when pH is above 6.5.

Permanently moist soils appear to be the most desirable as this condition maximises growth, yield and fruit quality. Except for a short period during the dry season (July), moisture stress can be detrimental to growth. The short period of moisture stress during the dry season induces flower initiation, which is beneficial. Supplementary irrigation may have to be applied in months with less than 150 mm rainfall. Although moisture stressed trees may still crop well initially, the size of the fruit will decrease and subsequent cropping will be reduced until the trees recover.

Because it is an understorey species in tropical rainforests, the mangosteen requires shading during early growth and development, and shelter throughout its life. Juvenile trees need to be shaded or else their growth rates will be substantially reduced and the trees may die. Shading of 30-50% with Sarlon type cloth rather than with other tree species is recommended for the first four years. Excessive shading (i.e. more than 50%) produces tall and skinny trees, which subsequently leads to poor and thin bearing surfaces. On the other hand, seedlings kept under full sunlight experience:

• stunted growth
• burnt leaves
• reduced leaf size
• reduced flushing frequency
• death.

Shading using other tree species has proven too difficult to maintain. At four years, shade can be removed between May and June and followed by foliage spray with very dilute flat plastic paint (1 paint: 20 water) or bentonite.

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Windbreaks

Flowering and fruit set can be severely limited by exposure to wind and low humidity. Planting of windbreaks is necessary in the wet tropics because of the cold south-easterlies during the cool dry period. Suitable windbreaks are jambolan (Eugenia cuminii), Pinus caribeae variety hondurensis and Casuarina species. However, the windbreaks will provide little protection from strong cyclonic winds. Inquire with your local forestry service for other suitable species.

The benefits of establishing windbreaks out-weigh the initial set-up costs. They improve yields, particularly during drought, and minimise leaf burn and fruit rub.

Cultivars

There are no identified varieties. No pollen is produced and the fruit is formed parthenocarpically - directly from the maternal tissue of the flower, like in mango fruit. Hence the seedling progeny are identical to the parent. Effectively, the mangosteen reproduces itself vegetatively. However, different types have apparently been found in different countries, but this is unlikely as tree and fruit characteristics may vary slightly with different environments. Distinction between the different types is based on fruit size, acidity and flavour.

There are two distinct fruit types or shapes: the more commonly planted is a round fruit and the other is ovoid or egg-shaped. Seed of the round type are currently preferred. There is little information on the production characteristics of the egg-shaped mangosteens.The yellow mangosteens are much easier trees to grow and bring to fruiting than the purple mangosteen. However, yellow mangosteens are frequently sour, but when cooked with plenty of sugar, they make an excellent pie filling. There are several species of yellow mangosteen:

• cv. mundu (G. dulcis)
• cv. kochin goroka (G. xanthochymus)
• cv. assam gelugur (G. atroviridis).

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Propagation and land preparation

Plant seed as soon as possible after extraction. Make sure all the pulp is removed from the seed. Larger seeds (greater than1.0 g) are generally preferred. Smaller seeds appear to produce variable germination and are slower growing. Seedling raising mix may be made up of peat and sand (pasteurised) in a 1:1 mixture. Lay the seed on the side and cover over with peat. 50 mm peat shell pots are recommended for individual seeds as there is no transplanting shock. As root bending may occur, place the peat pots on soil and not on a hard surface.

Re-pot from peat pots when roots begin to penetrate the base. Pots used are usually 250-400 mm deep and the soil mixture can be made up of peat, loam topsoil, and coarse sand using the ratio 1:1:2 (e.g.1 peat : 1 loam topsoil : 2 coarse sand). For community pots, when plants are hard mature or around 2 years, they can be transplanted. The addition of a slow release fertiliser, such as Osmocote Plus, improves the growth and vigour of the seedling. Seedlings will need regular fertilising, probably with a complete foliar nutrient spray. Field plant the seedlings when they are about 50 cm tall. Field planting should be done at the start of the wet season and watering commenced soon after planting to remove air pockets.

Deep ripping is recommended if the soil is compacted and to improve root penetration. In areas where waterlogging or ponding may occur, mounding is recommended. Bird manure, compost, and straw may be incorporated into the planting sites 6-9 months prior to planting.

Planting holes should be larger than the size of the plant containers in which the seedlings are nursed, usually 0.5 m deep and 0.5 m wide, and the trees should be at least 2 years from seed and 50 cm tall. Because fruits are formed on the periphery of the trees, plant or tree density will depend on:

• soil depth and quality
• topography
• plant variety
• irrigation.

Transplant seedling trees just before the wet season in a non-flushing state when they are around 18 months and about 600 mm height. Mangosteen seedlings can be planted at a density of 200-280 trees/ha. Minimum distances of 6 m between plants in the row and 6-8 m between rows are generally used, giving a total of 280 trees per hectare. Trees are later thinned to 12 m betweent plants in the row and 16 m between rows or hedgerows, leaving every second row. Some growers interplant with carambola (for short term yields) when spacings of 12 m by 16 m are used.

Shade must be provided immediately after planting, ensuring foliage is not exposed to full sunlight for any period. The shade enclosure should be 1.2-2 m above ground level.

Seedling trees and grafted trees are used for commercial plantings. Although there are some reports of increased growth using G.tinctoria and G.xanthochymus as nurse stocks, there is still no information proving that earlier or superior production can be achieved from grafted trees. Grafting has been shown in other tree species to provide precocity, desirable dwarfness and economy for picking and pruning. However, most Garcinia species are not compatible with mangosteens. Mangosteen is compatible when grafted on its own species, but the resulting tree appears extremely stunted and suckers profusely from just below the graft. The tree is not vigorous, needs to be staked upright and cannot support regular crops.

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Fertilising

Mangosteen are low maintenance trees. The fertiliser requirements are low for young trees. Mature bearing trees will need greater fertiliser inputs to ensure high yields. It is recommended that you get a soil and leaf analysis done.

Table 1 provides a general guide to fertilising mangosteen trees. The amounts will vary depending on tree age, stage of crop growth and development, and whether the tree is at a bearing age.

Dolomite is applied at the rate of 0.2 kg per tree per year of age and then at a constant rate after year 15. A preplant application of 15 g P as single superphosphate is generally given. Chicken manure may also be applied at the rate of 2 kg per tree per year. This is thought to improve the vigour and colour.

An example of a fertiliser program recommended by the Malaysian Agricultural Research & Development Institute (MARDI) for mangosteen is given in Table 2.

Mulching is generally practised. As mulch breaks down, it improves growth rates by providing nutrients and improving soil structure and soil moisture. Never place mulch against the tree trunk. 100-200 mm of bagasse, straw and compost is often used and is applied from near the trunk to 1 m beyond the canopy for young trees and for mature trees. Mulch can be applied in a 2 m wide band. Mulching is often carried out soon after the wet season and after July for bearing trees.

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Pruning

A general maintenance program, such as slashing and/or use of contact herbicides, to remove competition from surrounding weeds is recommended. During early growth, weeds around the tree trunk should also be controlled, taking care not to damage the young weak trees. Pruning of growing trees to remove dead, diseased, broken and misshapen limbs is good practice. A single trunk to at least 3 m in height is desirable. Dominant side branches and water suckers should be removed in juvenile trees. Following harvesting of fruit, any suckers and dry panicles are removed to promote healthy and vigorous regeneration of the crown. Any large cut surfaces should be treated with a bituminous paint.

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Harvesting and postharvest storage

Fruit colour change from green to red is an indication that the fruit is ready to be picked. The fruit is also quite edible at this stage, but maximum quality and shelf life is obtained from fruit picked at the uniform red stage. Fully purple coloured fruit is over ripe and undesirable as it will damage during packing and transport. Fruit is hand picked and is found on the periphery of the canopy. Pick fruit with the peduncle (fruit stalk) attached. Countries like Malaysia and Indonesia use a harvesting index to assist in determining the appropriate stage for picking (see Table 3).

If the fruit is further handled and processed, fruit should be harvested at colour index 3-5 and at colour index 5 (dark maroon violet) for immediate consumption. When picked at colour index 3-4, the skin is still resistant to mechanical damage during handling and will still develop the desirable maroon violet colour.

Generally fruit can be harvested 13-14 weeks after fruit set. Yields are variable and 400-900 fruit can be expected at each harvest from mature trees. In Malaysia, the mangosteen tree produces a yield of about 900 kg/ha in the first year of production and normally reaches maximum production of 28,000 kg/ha 24 years after planting.

In Queensland, a very heavy crop in a single season is usually followed by a number of smaller crops in the ensuing 2 to 3 years, although there is no apparent reason for this to occur. Whilst the main harvest season is March to June, small crops also come in October to December. A heavier crop in the latter part of the year will often follow a light main crop. The yield is variable and can range anywhere between 200 and 1000 fruit/tree/yr.

Fruit picked at the appropriate stage ("red stage") have a shelf life of 2-3 weeks at ambient or room temperature. After that period, the cortex (shell) hardens and it is difficult to open the fruit. However, the shelf life can be extended to 6 weeks if fruit is stored at 10°C.

Fruits are often cleaned following picking and graded according to the weight of each fruit. Fruit weight of less than 95 g is preferred. Pack only uniform quality red fruit. Fruit is often packed in a single layer in polystyrene or cardboard trays, ranging from 25-28 fruit per tray.

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Economics and market

Market fresh fruit soon after picking. Due to insufficient production data and a firm idea of market prices, the economics for mangosteen production is not established. Indications are that mangosteen production in northern Queensland has about an 8% internal rate of return.

Yields of 5550 kg/ha and a farmgate price of $8/kg used in calculations indicate a breakeven period of 20 years for mangosteen, with an initial investment of $191,100 required to establish a 5 ha orchard and with recurrent costs of $73,333/yr. Short term prospects for mangosteen are poor because of the long period to first fruiting and commercial harvest. Assuming good culture and maintenance of the crop, complete return on investment may be probable by the 15^th year.

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