Some high-quality dates are picked individually by hand, but most are harvested by cutting off the entire cluster. In North Africa, the harvesters climb the palms, use forked sticks or ropes to lower the fruit clusters, or they may pass the clusters carefully down from hand to hand.
Growers in California and Saudi Arabia use various mechanized means to expedite harvesting-saddles, extension ladders, or mobile steel towers with catwalks for pickers. All fruits in a cluster and all clusters on a palm do not ripen at the same time. A number of pickings may have to be made over a period of several weeks. In the Coachella Valley, dates ripen from late September through December and there are 6 to 8 pickings per palm.
Dates go through 4 stages of development: 1) Chirm, or Kari, stage, the first 17 weeks after pollination: green, hard, bitter, 80% moisture, 50% sugars (glucose and fructose) by dry weight; 2) Kuala stage, the next 6 weeks: become full grown, still hard; color changes to yellow, orange or red, sugars increase, become largely sucrose; 3) Rota stage, the next 4 weeks: half-ripe; soften, turn light brown; some sucrose reverts to reducing sugar which gains prominence; 4) Tamar stage: ripe; the last 2 weeks; in soft dates, the sugar becomes mostly reducing sugar; semi-dry and dry dates will have nearly 50% each of sucrose and reducing sugars.
Soft dates may be picked early while they are still light colored. Semi dry dates may be picked as soon as they are soft and then ripened artificially at temperatures of 80° to 95°F (26.67°-35°C), depending on the cultivar. Dry dates may be left on the palm until they are fully ripe.
Dry dates that have become too dehydrated and hardened on the palm are dehydrated by soaking in cold, tepid or hot water, or by exposure to steam or a humid atmosphere. Extremely dry weather will cause dates to shrivel on the palm. In the Sudan, the fruits are picked when just mature and then are ripened in jars to prevent so much loss of moisture. Rain, high humidity or cool temperatures during the maturing period may cause fruit drop or checking, splitting of the skin, darkening, black nose, imperfect maturation, and excessive moisture content, or even rotting. Under such adverse weather conditions, as may occur in the Salt River Valley, Arizona, dates must be harvested while still immature and ripened artificially.
In the Old World, there are many different methods of doing this: storing in earthen jars, placing the jars in sun hot enough to prevent spoilage, boiling the fruits in water and then sun drying. In Australia, entire clusters are kept under cover with the cut end of the stalk in water until the fruits are fully ripe. In modern packing houses, prematurely harvested dates are ripened in controlled atmospheres, the degrees of temperature and humidity varying with the nature of the cultivar.
Where there is low atmospheric humidity outdoors and adequate sunshine, harvested dates is sun dried whole or cut in half. For fresh shipment in California, the normally ripe, harvested fruits are carried to packing plants, weighed, inspected by agents of the United States Department of Agriculture, fumigated, cleaned, graded, packed, stored under refrigeration, and released to markets according to demand. Saudi Arabia has constructed a number of extra-modern processing plants for fumigation, washing, drying, and packing of dates prior to cold storage.