The picking process offers no particular problems, although the methods are not the same with all varieties. Usually two persons can pick together conveniently, one holding the basket and the other gathering the dates and placing them in it. Under favorable conditions, some varieties will mature a whole bunch so evenly that it can be removed entire without loss, but in many cases it is necessary to pick out the different "threads" carrying dates, and cut them separately, leaving those whose fruit is not yet mature for another day. It is advisable, with kinds that permit of it, to leave the calyx on the fruit, since if this is pulled off it opens an avenue for the entrance of insects and dirt. Bunches left to ripen on the tree frequently need to be protected by a bag of cheese-cloth or similar material, to keep off birds and insects.
Dates grown for home use need no treatment after picking unless it be a washing to remove the dust. If they are to be kept for some time, they may well be pasteurized to free them of insect eggs and the bacteria of fermentation and decay. Small quantities of fruit can be treated successfully in the oven of a cookstove, pains being taken by regulating; the aperture of the door, to keep the temperature between 180° and 190° for three hours. This may slightly alter the taste; sterilization by exposure overnight to the fumes of carbon bisulfide is easy and causes no change of flavor.
There are many advantages in ripening dates artificially rather than leaving them to mature on the tree; hence some method of artificial ripening has been practiced in most date-growing countries since the time of the earliest written records. Much careful experimentation has been done in this country, first by the Arizona Experiment Station and later by the United States Department of Agriculture. As a result, such simple, satisfactory, and inexpensive methods of maturing dates have been worked out that the commercial grower will do well to rely on them. The exact process differs with the variety and with the conditions under which the dates have to ripen; for the precise technique advisable in his case the grower must either refer to those who have had the experience he needs, or experiment on a few dates for himself, after he has grasped the general principles.
As W. T. Swingle points out, a date is botanically mature, or "tree ripe" as horticulturists say, as soon as it reaches full size and the seed is fully developed. At this stage, however, the date is still astringent and not eatable. Following this comes a process that may be called "ripening for eating," consisting of complex chemical transformations by which the sugars are altered and the tannin deposited in insoluble form in "giant cells." This final ripening is brought about by the combination of heat and a certain degree of humidity.
The principle underlying modern methods of artificial ripening is, therefore, to expose the dates to a constant high temperature, while holding them in the humid atmosphere which is created by the moisture they naturally give off as they dry and wrinkle.
For this purpose the dates are picked when they first begin to soften. Most varieties at this stage show translucent spots while the remainder of the berry is still hard and remains bright red or yellow in color. Dates taken from the tree in this condition will ripen successfully in three or four days if they are packed loosely, stems and all, into a tightly closed box and left at ordinary room temperature, the room being closed at night to keep out cold air. Commercial growers provide a special house, or a room built in the packing-shed for this purpose. This is so constructed as to be air-tight when closed, so that the temperature can be maintained at an even figure, without variation of more than a degree or two, by means of an electric light or a lamp with thermostat attachment such as is used in the incubators of poultrymen. Under such conditions, dates will be brought to a beautiful even maturity and practically without loss by keeping them from twenty-four to seventy-two hours at a temperature of 110° to 120°.
The skillful grower will control further the ripening of his dates by irrigation. In some climates, like that of Upper Egypt and of the Coachella Valley in some seasons, a typically "soft" date like Deglet Nur will mummify on the palm, as it matures, until it becomes a "dry" date. This can be avoided by keeping the palms well irrigated while the dates are ripening. On the other hand, "soft" varieties sometimes "go to pieces" and ferment on the tree, because of too much moisture; in this case the soil must be kept dry during the ripening season.
The packing of dates is a matter for the grower's own taste, or for standardization by the cooperative association to which he may belong. Good dates of standard varieties are usually packed in layers in one-pound cardboard boxes, like sweetmeats. In California, where home-grown dates bring fancy prices, great pains are taken with this finest quality of fruit, which is easily retailed at $1 a pound.
Most dates worth marketing in the United States are worth packing in cartons. In Arizona, berry-boxes have been used. The American standard for bulk shipment is the lug-box of 30 to 40 pounds' capacity. It is important, in any case, that the pack be uniform, both in size and variety; otherwise the grower can expect to receive only "cull" prices.
Many varieties, such as Zahidi, ripen well in the bunch and adhere indefinitely. It is probable that a profitable trade can be developed in marketing entire bunches of these, which the retail dealer can display in his store as he does a bunch of bananas. Dates of inferior quality can be worked up into various by-products, such as "date butter," or sweetmeats, or may be sold to bakers and confectioners. Culls are used in the Orient for the distillation of arrak, or as feed for live-stock. Soft early dates, which in many cases are of a beautiful color as well as delicious flavor but which lack keeping quality, probably could be sold in crates as are berries and be similarly handled as perishable fruits. Marketing should be carried on through a growers' cooperative association, which can guard the interests of all by insisting on proper standards.
For a bearing plantation with fifty palms to the acre, 100 pounds of fruit to a tree each year is a conservative estimate of the yield. This means 5000 pounds of fruit an acre each year, the retail value ranging from 2 cents a pound in the Orient to $1 a pound in the United States. Growers in the Coachella Valley have been able for some years to sell practically all the good dates they produce at 25 cents to 75 cents a pound at the plantation. Such a price is not likely to be maintained, since dates of many varieties can be grown, picked, and packed at a total cost of not more than 5 cents a pound; but there are no present indications of an early decrease in price. If it should fall to an average of 20 cents a pound, this would still allow the satisfactory gross income of $1000 an acre from fruit alone, while the offshoots of good varieties at present prices ($5 to $15 each) are a valuable factor and may be worth almost as much to the orchardist as the fruit. Offshoots, in fact, should more than pay the whole cost of running a young plantation, leaving the entire proceeds from the fruit as clear profit.