In regard to soil, the species is not exacting but it is considered to succeed best on deep, rather heavy, loams. It is on soils of this type that the excellent pomegranates of Mesopotamia are grown. A small amount of alkali is not injurious, nor does excessive moisture seem as detrimental to the pomegranate as to many other fruit-trees. George C. Roeding remarks: "I have used the pomegranate for a number of years in depressions in my vineyard where the ground was so damp for a good part of the year that grape vines invariably died. The pomegranate luxuriates in these spots."
When planted in orchard form, the bushes should be set 12 to 18 feet apart. Pomegranates are often planted in hedgerows, and under such conditions are ordinarily not more than 6 or 8 feet apart; but close planting and the permitting of development of suckers from the base of the plant naturally are detrimental to fruit-production.
Cultural practices in California have been described by Robert W. Hodgson, in "The Pomegranate." 1 The following extracts are taken from his publication:
"Pomegranate trees should be planted as early in the spring as the ground can readily be worked and is not too wet. However, as the pomegranate starts growth comparatively late in the spring, late planting is not accompanied by such disastrous effects as with the stone fruits. The best results seem to be obtained by planting in February and March.
"If the soil is in good condition, little care other than irrigation and two or three cultivations during the season is needed after planting. In older orchards the soil should be stirred at least once a month during the growing season.
"Some growers irrigate but little, while others apply as much as they give their citrus orchards. ... If we set the water requirements of orange trees at fifty inches, including the rainfall, we may consider that the pomegranate requires thirty-five to forty inches. Some of this water comes as rain in the winter season. The rest is usually applied in two to five irrigations, distributed through the growing season. Some growers irrigate until July only. Others apply water once a month until September. The furrow system is used almost universally.
"To prune intelligently, one must consider the fruiting habit, and habit of growth of the tree. The pomegranate is a vigorous grower, sending up each year a number of shoots from the root which gives the plant a bush form unless otherwise trained. The fruit is borne terminally on short spurs produced on slow-growing mature wood. This wood bears for several years, but as the tree increases in size this wood loses its fruiting habit, which is assumed by the younger growth. Little or no fruit is produced in the interior of the tree.
"Bearing this in mind, it can clearly be seen that a heavy pruning, especially shortening in of the older wood, will greatly reduce the crop for the next two or three years.
"When the tree is planted it should be cut back to a whip at about 24 to 30 inches from the ground. As the buds put out and shoots are produced, these should be selected and thinned out to three or five or more scaffold branches which should be pinched back to make them stocky. These should be spaced some distance apart, - the lowest at least eight or ten inches from the ground, - and symmetrically arranged on the stem. The following winter the scaffold branches should be shortened to about three-fifths of their length. In the spring the new shoots arising from the scaffold branches (primary branches) should be restricted to two or three per limb. The main stem and frame limbs should be kept free from suckers at all times. The aim in pruning while the tree is young is to induce the formation of a stocky, compact framework. This should be accomplished by the end of the second or third year.
1 Bull. 276, Calif. Agr. Exp. Sta.
"After the framework is established all the growth is left and the tree comes into bearing. From this time to the age of 15 or 20 years, the tree increases slowly in size and yield. Pruning after the third year should be confined to a regular removal of all sucker growth arising from the root, and interfering branches as well as dead brush, and an annual thinning out or removal of some of the older branches. This should be done after the leaves fall in winter."
Propagation of the pomegranate is effected by means of seeds, cuttings, and layers. Seeds can be grown readily, but named varieties cannot be reproduced in this manner. Hodgson writes:
"The only method of propagation used commercially is by hardwood cuttings. These will grow in the open ground about as readily as willow cuttings. The stand obtained is very satisfactory and the method used very simple. In February or March hardwood cuttings ten to twelve inches long and one-quarter to a half inch in diameter are cut, usually from the shoots or suckers, and are planted in the open ground in nursery rows. These rows are ordinarily three feet apart and the cuttings spaced eight to ten inches in the row. The cuttings should be thrust almost their entire length into the earth, leaving only the top eye exposed. This eye is forced out and grows into the tree. Cuttings of this sort grow thriftily and are often ready for transplanting to the orchard or hedge by the following spring, although they are frequently left in the nursery row two seasons. Hardwood cuttings are sometimes cut in the fall and callused in sand over winter, then set out in early spring. This may result in a little earlier growth and consequently a larger tree that season, but is not necessary to insure striking root."
When grown under good cultural conditions, the plants come into bearing at three or four years of age. The yield is influenced by the character of soil and the method of pruning followed. On sandy soils light crops must be expected; and if suckers are allowed to develop unhindered, or if the mature plant is pruned of its fruit-bearing wood, little fruit can be produced. It is necessary to emphasize the importance of pruning in connection with pomegranate culture. A properly grown tree of mature size may yield 200 to 400 pounds of fruit annually, but one which has been subjected to incorrect pruning, or has a number of primary shoots growing from the base instead of a single trunk with laterals rising from it, will certainly give no such results.