Horticultural writers have asserted that the mangosteen can be grown only within four or five degrees of the equator. Experience has shown that such a statement is not warranted by facts. It is true that the tree is strictly tropical in its requirements and that its demands in regard to soil conditions are definite. There is no reason, however, to assume that it will not be possible to grow mangosteens successfully throughout the tropics wherever these conditions can be met. Fair-child considers that the unduly limited distribution of the tree is due to the difficulty which young plants have in establishing themselves, and he believes that a vast extension of mangosteen culture will take place when the root-system of this tree is thoroughly understood. "This may come about through the use of stocks which are less particular in their soil requirements. George Oliver's experiments have proved that the mangosteen can successfully be inarched upon a number of the related species of the same genus." Thus, on Garcinia xanthochymus, a vigorous and hardy species, it has done remarkably well. Since more than 150 species of Garcinia are known, there should be excellent possibilities of obtaining a stock-plant which will produce robust mangosteen trees on soils where they will not grow successfully on their own roots.
1 Die Pflanzenstoffe.
The mangosteen does not withstand frost, but the behavior of trees in Cuba and elsewhere shows that it is not injured by merely cool weather; that is, the constantly high temperatures of the equatorial belt are not essential to its success. Like the breadfruit and a few other strictly tropical species, it does not like temperatures below 40° or thereabouts. In Ceylon and Singapore the best orchards are on soils having a high clay-content, combined with plenty of coarse material and a small amount of silt, and where the water-table stands about six feet below the surface. "The impression is current," says Fairchild, "that the mangosteen requires a wet but well-drained soil and a very humid atmosphere. While the former statement appears to be true, the latter is not so, for the tree which has fruited on the island of Kauai (Hawaii) is in a dry but irrigated part of the island, with only six inches of rainfall, where it has to be irrigated twice a month."
The observations made by Fairchild during his studies of mangosteen culture in the Orient are of such importance that it is worth while to reproduce some of them here. He writes of his visit to W. H. Wright at Mirigama, Ceylon:
"His orchard consisted, at the time of my visit in 1902, of 23 trees and was then probably the largest in the colony. It was from eight to ten years old, having been planted with two-year-old trees which were sent him as a present from the Malay peninsula. The selection of a site for his orchard was a very happy one; a moist spot in his coconut plantation, a part of which had at one time been used as a rice field. The ground was so moist that open drains were cut through it to carry off the superfluous water and these are still kept in order. The soil of the squares on which the trees are growing is so moist and soft that, were it not for a layer of coconut husks, one's feet would sink in up to the ankle as he walks across them. The roots, under these circumstances, are bathed continually in fresh, not stagnant, moisture. Mr. Wright attributes his success in growing mangosteens to the fact that he has planted them on soil that never dries out, but has, at a few feet from the surface, a continual supply of fresh moisture. The water in his well, near by, is six feet from the surface of the ground. H. L. Daniel, who has been for 15 years trying to grow this fruit, and who, during that time, has planted over a hundred young trees, assures me that this is one of the secrets of the culture of this difficult fruit, and gives Mr. Wright credit for first finding it out.
"Another important detail relates to the matter of transplanting the young seedlings. Mr. Daniel plants the seeds in a small pot or coconut husk, and keeps them well watered and slightly shaded with a coarse matting of coconut leaves. He transplants them from this small pot to a larger one when the roots have filled it; and in removing he cuts off the tap-root if the latter is exposed. For two years these young plants are kept in pots and grow to a height of two to two and a half feet. It is useless to transplant them before they are at least two feet high, for the check given them, if too young, by the transplanting is so great that they refuse to grow.
" When transplanted, the plants are set in a hole three feet cube in size. Stiff soil is best but is not absolutely necessary, as they will grow in a light soil if the subsoil is a good paddy mud. From the first the young trees should be shaded with a matting of coconut leaves, which is suspended two feet or so above the top of the plant. This is to prevent wilting and subsequent death of the two red, partly developed leaves, which first appear from the seed, and which must be kept alive if the plant is to make a rapid growth. If these precautions of potting, shading, and selection of soil are followed, trees should come into bearing seven years from seed, producing a small crop of a hundred fruits or so. The subsequent treatment of the mangosteen orchard seems to be very simple, - no pruning of any kind is commonly practiced, although it might be advisable to prune; and little cultivating is done. A mulch of coconut husks about the base of the tree to keep the surface soil continually moist, and the application of a small amount of earth from the poultry-yard, sprinkled about underneath the trees each year, are the only attentions given them. Whether or not artificial fertilizers could be employed with profitable effect is a question that has not been answered."
In the same article 1 Fairchild writes of mangosteen culture in another region:
"In Singapore there are some small mangosteen orchards, that is, mangosteens mixed with other fruits. One which is easily accessible lies on the well-known road to the Botanic Gardens, some two miles from the Raffles Hotel. The land is low and wet and several drainage canals cut it up into large, square blocks. The soil is clay and evidently saturated with moisture. About each tree is a circular bit of cultivated soil, the rest being in grass, and scattered over the bare soil under the trees is a mulch of leaves and coconut husks. I do not know how old the orchard is, but it is presumably about 30 years of age. . . . Dr. Ridley, then Director of the Botanic Gardens in Singapore, remarked that though apparently in excellent condition this orchard was not productive. It was his belief that it needed pruning and his experience with a tree in Government House Gardens bears out his belief. He cut out the innermost branches from one of the lot of old mangosteen trees there, which had not borne well for years, and as a consequence it produced, the next year, an abundance of fruit. His opinion is that the trees should regularly be pruned of all the small inner branches."
Regarding the behavior of the mangosteen in Hawaii, Fair-child says: "Francis Gay, who planted the tree at Makaweli, Kauai, wrote that where the tree is growing the water is about six feet below the surface of the soil, that the tree is irrigated twice or three times a month, and that the rainfall of the region is six to seven inches a year. This tree of Mr. Gay's is about 25 years old, fruited first when ten years old and now bears only a few fruits per year. ... It stands about 15 feet above sea-level in a spot well-protected from the winds by windbreaks and is growing on a sandy, alluvial soil."
1 Journal of Heredity, Aug., 1915.