In general it must be considered that the litchi is tropical in its requirements. It likes a moist atmosphere, abundant rainfall, and freedom from frosts. It can be grown in subtropical regions, however, where the climate is moist or if abundant water is supplied, and where severe frosts are not commonly experienced.
Young plants will not withstand temperatures below the freezing point. In regions subject to frost they should, therefore, be given careful protection during the winter. The mature tree is not seriously injured by several degrees of frost, but at Miami, Florida, plants six feet high were killed by a temperature of 26° above zero.
Rev. William N. Brewster of Hinghua, Fukien, China, describing the conditions under which the trees are cultivated in that country, says: "They will not flourish north of the frost line. They are particularly sensitive to cold when young. It is the custom here to wrap the trees with straw to protect them from the cold. After the trees are five or six years old they are less sensitive, and it takes quite a heavy frost to injure them."
Regarding soil, G. W. Groff of the Canton Christian College writes : "The litchi seems to do best on dykes of low land where its roots can always secure all the water needed, and where they are even subjected to periods of immersion. In some places they grow on high land but not nearly so successfully." The Rev. Mr. Brewster says on this subject: "The trees flourish in a soft, moist black soil; alluvium seems best. Near by or on the bank of a stream or irrigation canal is best, though this is not essential. Where there is no stream the trees should be watered so frequently that the ground below the surface is always moist; about twice a week when rain is not abundant should be enough. After the young trees are well started, about two or three years old, the irrigations may be less fre-quent."
These authorities are quoted to show the conditions under which the litchi is grown in China. Experience in other countries has shown the tree to be reasonably adaptable in regard to both climate and soil. While it prefers a humid atmosphere, it has succeeded in the relatively dry climate of Santa Barbara, California, without more frequent irrigation than other fruit-trees. On the plains of northern India, where the atmosphere is comparatively dry and the annual rainfall about 40 inches, it is cultivated on a commercial scale. Although the best soil may be a rich alluvial loam, it has done well in Florida on light sandy loam. It has not been successful, however, on the rocky lands of southeastern Florida. Whether these lands are too dry, or whether the litchi dislikes the large amounts of lime which they contain, cannot be stated definitely. In undertaking to grow this tree, four desiderata should be kept in mind : first, freedom from injurious frosts; second, a humid atmosphere ; third, a deep loamy soil; and fourth, an abundance of soil-moisture. When one or more of these is naturally lacking, efforts must be made to correct the deficiency in so far as possible. Frost-injury can be lessened by protecting the trees; low atmospheric humidity is not badly prejudicial if the soil is abundantly moist; sandy soils may be made more suitable by adding humus-forming material; and a soil naturally dry may be irrigated regularly and frequently.
In regions where the litchi tree grows to large size, it is not advisable to space the plants closer than 30 feet apart, and 40 feet is considered better. In Florida they can be set more closely without harm; 25 feet will probably be a suitable distance. In localities where frost protection must be given, it may be desirable to plant the trees under sheds, and in this case economy will demand that they be crowded as much as possible. At Oneco, near Bradentown, Florida, E. N. Reasoner has fruited the litchi very successfully in a region usually considered too cold for it, by growing it in a shed covered during the winter with thin muslin to keep off frost, and opened in the summer. If it is commercially profitable to erect sheds over pineapple-fields, - and it has proved so in certain parts of Florida, -there seems to be no reason why it should not be much more profitable to grow the litchi in this way, in regions where protection from frost is necessary.
The trees should be planted in holes previously prepared by excavating to a depth of several feet, and incorporating with the soil a liberal amount of leaf-mold, well-rotted manure, rich loam, or other material which will increase the amount of humus. This is, of course, more important where the soil is light and sandy, as it is in many parts of Florida, than where the humuscontent is high. Basins may be formed around the trees to hold water.
Bonavia writes: "As the trees grow, their thalas or water-saucers should be enlarged and on no account should the fallen leaves be removed from them, but allowed to decay there and form a surface layer of leaf-mold. . . . Every hot weather thin layers of about two or three inches of any other dried leaves should be spread over the thalas, and allowed to decay there, to be renewed when they crumple up and decay." This corresponds to the mulching generally practiced in western countries. It has been remarked by several writers that the litchi is a shallow-rooted tree, with most of its feeding roots close to the surface. If this really is the case, mulching will probably be an essential practice, and deep tilling of the soil will have to be avoided.
Rev. Mr. Brewster says: "Fertilization is important. Guano is probably as good as anything. The Chinese use night soil. They dig a shallow trench around the tree at the end of the roots and fill it with liquid manure of some sort. This is done about once in three months." J.E. Higgins, 1 in his bulletin "The Litchi in Hawaii," notes that "Some growers prefer to put the manure on as a top dressing and cover it with a heavy mulch because of the tendency of the litchi to form surface roots."
The tree requires little pruning. Higgins says : "The customary manner of gathering the fruit, by breaking with it branches 10 to 12 inches long, provides in itself a form of pruning which some growers insist is necessary for the continued productivity of the tree." But a thorough study has yet to be made of this subject in the Occident.
Hand-in-hand with the development of litchi-growing in the American tropics and subtropics will come the development of new cultural methods. The information at present available is meager, and too apt to be characterized by the generalities of the Hindu horticulturist: "Too much manure should not be applied to newly planted or small trees. As the tree flourishes, more and more manure should be applied," writes one of them, in a treatise on litchi-culture. The literature of tropical pomology is burdened with information of this nature, and the need is for more specific data based on experience.
1Bull 44, Hawaii Agri. Exp. Sta., 1917.