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Phoenix dactylifera L.

Arecaceae
Date palm

Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.

  1. Uses
  2. Folk Medicine
  3. Chemistry
  4. Description
  5. Germplasm
  6. Distribution
  7. Ecology
  8. Cultivation
  9. Harvesting
  10. Yields and Economics
  11. Energy
  12. Biotic Factors
  13. References

Uses

The Arabs say that there are as many uses for dates as there are days in the year. Cultivated primarily for fruit eaten fresh or dried, being a high energy food of high sugar content, as well as a good source of iron and potassium. A date diet is low in fats and proteins; hence the Arabs eat them habitually with some form of milk (Tackholm and Drar, 1973). Fruits often preserved by drying or pressing them together into large cakes. Other products include date honey, made from juice of fresh fruit; date sugar; date sap, often made into a fermented beverage; date palm flour, made from pith of tree; the palm heart, eaten as a salad; oil from seeds; the kernels are ground up or soaked in water for days and used for animal food; seeds are also strung as beads; both wine and honey are derived from the date; in medevial days, the palm was thought to prevent sunstroke, avert lightening, cure fevers, and drive away mice and fleas. Mats are woven from the leaves, while the fibers provide thread and rigging for boats. The leaf midribs are used for fencing and roofing. There is sap in the palm tree which, after fermentation, is used as a liquor. Sap, collected in the morning, may contain 4–5% alcohol by evening. Seed oil used for soap manufacture. The wood from the trunk is cut into planks, used for doors, beams, and rafters.

Folk Medicine

Regarded as aphrodisiac, contraceptive, demulcent, diuretic, emollient, estrogenic, expectorant, laxative, pectoral, purgative, refrigerant, the date is listed in folk remedies for ague, anemia, asthma, bronchitis, cancer, catarrh, chest, condylomata, cough, diarrhea, eyes, fatigue, fever, flu, gonorrhea, endurations, longevity, piles, pterygia, splenitis, sterility, stomachache, thirst, toothache, tuberculosis, urogenital ailments, vaginitis, virility, warts, and whitlows (Duke and Wain, 1981). Hartwell (1967–1971) mentions cancers, indurations or tumors of the abdomen, gum, liver, mouth, parotids, spleen, stomach, testicle, throat, uterus, and viscera. Medicinally, fresh juice is cooling and laxative; gum useful in treatment of diarrhea and diseases of gentio-urinary system; fruit is deculcent, expectorant, anti-scorbutic, nutrient, laxative, aphrodisiac, and is prescribed in asthma, chest complaints and cough, fever, and gonorrhea. A plaster of the nuts or of the bark is a folk remedy for whitlows, hardnesses, and scirrhi. Tackholm and Drar (1973) report on one "superstition" that may have a scientific rational behind it. "The pollen of a male date palm mixed with water is a charm against childlessness. If you consult the chemistry paragraph, you will see that the pollen contains estrogenic hormones. Egyptians also believe that to swallow one, two, or three date stones will prevent child-bearing for many years.

Chemistry

Pollen, containing cholesterol and estrone, exhibits gonadotrophic activity on immature rats. Per 100 g, the fruit pulp is reported to contain 317 calories, 15.3 g H2O, 2.5 g protein, 0.4 g fat, 75.8 g carbohydrate, 3.9 g fiber, 2.1 g ash, 120 mg Ca, 50 mg P, 7.3 mg Fe, 26 mg b-carotene equivalent, 0.01 mg thiamine, 0.02 mg riboflavin, 0.9 mg niacin, and 3 mg ascorbic acid (C.S.I.R., 1948-1976). The Wealth of India also reports the mineral composition of exotic dried dates 754 mg K/100 g, 68 mg Ca, 58 mg Mg, 1.6 mg Fe, 0.21 mg Cu, 64 mg P, and 51 mg S/100 g. Zinc, arsenic, and 6.3 mg I/100 g were also reported. On the other hand, Vandercook et al. (1980) tabulate data of importance to those interested in higher potassium—lower sodium diet.

Inorganic constituents of dates
(mg/ 100 g dry weight)
Element Halawy Sayer
Potassium 716.0 657.0
Sodium 37.0 38.0
Calcium 65.0 97.0
Magnesium 71.0 79.0
Phosphorus 84.0 63.0
Iron 3.7 3.1
Aluminum 5.1 --
Copper 0.2 0.2
Sulfur 52.0 59.0
Manganese 3.3 4.6
Silicon 66.0 66.0
Chlorine 27.0 31.0
High potassium diets recently were shown to retard or prevent the development of gastric ulcers in experimental rats. According to Kikuchi and Miki (1978) the sarocarp contains cholesterol, campesterol, stigmasterol, b-sitosterol, and isofucosterol. The dry date seed contains 7.9% moisture, 5.2% protein, 6.8% fat, 65.5% carbohydrates, 13.6% fiber, and 0.89% ash. The fatty acid composition of the seed oil is 8% lauric, 4% myristic, 25% palmitic, 10% stearic, 45% oleic, and 10% linoleic with some capric and caprylic acids as well. Jaggery, made from the sap of the tree boils down to 9.6% moisture, 86.1% carbohydrates, 1.5% protein, 0.3% fat, 2.6% minerals, 0.36% Ca, and 0.06% P. Leaves, used for manure, contain 0.4–0.66% N, 0.025–0.062 P, 0.33–0.66 K, and 10.0–16.4% ash. Fruit stalks contain 0.28–0.42% N, 0.017–0.04% P, 3.46–4.94% K, and 7.7–9.88% ash (C.S.I.R., 1948–1976). One unexpected compound in date tissue is serotonin at levels of 850 mg per 100 g. Acetaldehyde is the major volatile aldehyde in date. Chlorophyll in Iranian green Shahani dates drops from 410 mg/g fresh date to 0 in ripe brown dates (Vandercook, et al, 1980). Traces of coumarin occur in the leaves and leaf stalk. Leaves contain luteolin-7-glucoside, luteolin-7-rutinoside, and glycosylapigenin. Pollen contains cholesterol and rutin. The hemicellulose of the pollen contains 46% arabinose, 25% galactose, 18% xylose, 9% rhamnose, and 2% uronic acid. Seeds contain cholesterol estrones, polysaccharide A (with 10:1 D-mannose:D-galactose) polysaccharide B, and xylose. The fruit pulp also contains leucanthocyanins, pipecolic acid, 5-oxypipecolic acid, (C6H11NO3) and the piperidine derivative baikiain (C6H9NO2) as well as tannin.

Description

Dioecious tree (rarely monoecious) to 30 m tall. Leaves pinnate, 4–8 m long, with pointed enduplicate leaflets, with persistent leaf bases and a terminal crown of 100–120 leaves. Flowers small, white, on a richly branched spadix, surrounded by a solitary, large spathe. Calyx cup-shaped, 3-toothed, petals 3, in female flowers twice as long as the calyx. Stamens 6 with linear dorsifixed anthers. Ovaries 3, only one developing into fruit. Fruit usually cylindrical, occasionally rounded or ovoid, 2.5–7.5 cm long, with fleshy, sugary pericarp, yellowish to reddish brown (Takholm and Drar, 1973; Purseglove, 1972).

Germplasm

Reported from the African Center of Diversity, date, or cvs thereof, is reported to tolerate alkali, drought, frost, heat, heavy soil, high pH, salt, sand, slope, smog, and waterlogging for brief periods (Duke, 1978). Barrett (1973) lists the following sources for desirable characters in a date breeding program:

Table 1. Source of some desirable characters used in the date-breeding program
Variety Desirable Characters
Abbada Attractiveness, glossy black-fruit with frost-like bloom, midseason maturity.
Amir Hajj High quality, little spoilage of fruit in wet weather.
Barhee High quality, heavy yield, late maturity, low tannin in khalal stage.
Bedraya Large fruit, firm texture, midseason maturity.
Dayri High quality, distinctive rich flavor, moisture tolerance, good size, semidry texture.
Deglet Beida Light-colored fruit, smooth skin, very firm texture, early maturity.
Deglet Noor Superior quality, distinctive rich flavor, semidry texture, long fruitstalks.
Empress High quality, attractiveness, good size, distinctive rich flavor.
Halawy High quality, distinctive rich flavor, moisture tolerance, early maturity.
Horra Good size, very firm texture, long fruitstalks, midseason maturity.
Khadrawy High quality, dwarf stature, moisture tolerance, precocious flowering, sparse spines,early maturity.
Kush Zebda Superior fruit quality, distinctive rich flavor, long fruitstalks.
Medjool Large fruit, moisture tolerance, early maturity, good quality.
Tadala Large fruit, moderate moisture tolerance, attractiveness, early maturity.
Thoory Light-colored fruit, moderately large fruit, very firm, moisture tolerance, late maturity.
Tackholm and Drar discuss many of the Egyptian cvs. and Knight (1980) some of the American grown cvs. "Since 1913 the largest collection of date-palm varieties ever made from the chief growing centres in the East was tried in Arizona and California...". (2n = 28, 36)

Distribution

Not known in the wild state, cultivated and subspontaneous throughout the desert regions between 15° and 35° N, from the Canaries and Morocco in the west to India in the east. Recorded from all the inner and littoral parts of N. Africa, from the southern parts of Balkan Peninsula and Asia Minor, from Syria, Palestine, Transjordania, Iraq, Arabia, Iran, Baluchistan. Cultivated as an ornamental in S. Europe, but seldom matures fruit except in extreme southern parts of Italy and Spain. Cultivated in Arizona and California, USA, and Queensland, Australia. There is evidence of date usage 8000 years ago in W. India as well as its cultivation in Sumeria and the ancient Egyptian empire (Knight, 1980).

Ecology

Ranging from Tropical Desert to moist through Warm Temperate Thorn (with mild frost) to Dry Forest Life Zones, date palm is reported to tolerate annual precipitation of 3.1 to 40.3 dm (mean of 16 cases = 11.1), annual temperature of 12.7 to 27.5°C (mean of 16 cases = 22.2), and pH of 5.0 to 8.2 (mean of 12 cases = 6.5) (Duke, 1978, 1979). A full bearing orchard requires the equivalent of 23 dm rainfall (Knight, 1980). Some of the date palm's peculiar ecological whims include: It is very tolerant of alkali soils and can grow in soils containing 3–4% white alkali; but to bear well, the palm's roots must be in a stratum with less than 1% of alkali silts. Grown ideally where the permanent water table is within of the soil surface. At least 8 to 9 acre feet of irrigation water per year is necessary for good production on bearing palms. Daytime temperatures of 50°C are tolerated. For proper ripening of fruit, the mean temperature between the period of flowering and ripening should be above 21.2°C rising to 26.7°, for at least a month. Finest date varieties require 3300 units of heat, a unit being defined as degree above a daily mean of 64.4°F between the flowering, fruit development, and ripening periods. Israelis blame some of their problems on inability to control the flowering date. (It takes 6 months for the fruit to ripen.) There can be some control by withholding irrigation during fall and winter. There must be no rain during flowering time. An average temperature of 30°C is good for proper ripening. Winter temperatures below -8°C (ca 17°F) are harmful. Any good soil that is not too heavy will do. In clean soil, a little hard water is OK; in alkaline soil, clean water is OK; but the combo of alkaline soil and salty water is too much. Dates do well even where there is a crust of salt on the surface. If in the top 2–2.5 m there is a 30-cm layer or strata with 1% alkalinity, the date roots will "find" the strata and flare out there.

Cultivation

Propagated by seed or off-shoots. Seedlings are first planted in nursery rows and later transplanted to their permanent location. Sometimes planted around Aswan, they plant several seedlings in the same hole to insure the presence of females. Normal healthy trees may produce 10–30 or more offshoots. These will root if their bases are encased in soil. In Egypt they say it takes 8 years for an offshoot to yield economically. Elsewhere they are planted ca 9 m apart with one male per 50 or more females. Arabs tend to space them at 5.8 x 5.8 m. Offshoots are buried firmly up to their maximum diameter, taking care that the crown remains 10–15 cm above the soil so that irrigation water does not touch it. They need protective wrapping or shelter against cold, heat, and wind. In early stages, manuring is productive and palms may be intercropped with low crops like barley, pulses, and wheat. When the palms are taller, apricots, figs, grapes, oranges, peaches, pomegranates, etc. are intercropped. Pruning of the leaves, artificial pollination (described in Ur ca 2,300 BC), and thinning of the fruits also recommended. Pollination is helped along by placing cut portions of the male flower spikes in the receptive female inflorescence. Recent breakthroughs in tissue culture propagation (Tisserat, 1979) bode well for the expansion of date production.

Harvesting

In Egypt, dates usually flower in February and March, ripening in August and September. Precocious trees may start fruiting at 2–3 years, but full crops are not usual until 5–8 years old. Tackholm and Drar relate a peculiar type of rejuvenation used with date palm: Old or damaged trees are rejuvenated by making a horizontal hole 4 m below the summit. A wooden cylinder is pushed into the hole, and the place surrounded by earth kept in baskets. Roots are soon produced at this spot. Later, it is possible to cut off the trunk below the wooden cylinder and transplant the summit. It will start carrying fruit again. There are known cases where such operations have been successfully performed on the same tree 4 times (Tackholm and Drar, 1973). Trees may bear for a century or more.

Yields and Economics

In Egypt, palms yield 5–30 bunches, averaging 12, each bunch containing 5–15 kg dates, suggesting average yields of 120 kg date/tree/yr (Tackholm and Drar, 1973). According to Duke (1977b), "A single date palm may yield 120–280 liters of toddy and 40–80 kg of dates, or 7–10 MT of dried dates per hectare." World exports averaged around 350,000 MT in 1975. Iraq accounting for more than 75%, Iran less than 10%. Algeria accounted for ca 3.3%, Tunisia, 1.4%. During this same period, the US produced more than 20,000 MT (since declined), importing ca 14,000 MT and exporting ca 6,500 MT.

Energy

Yields as high as 250 kg per tree are recorded in California and Arizona, but a farmer with 50 kg per tree should be satisfied. Israelis reported 15–66 kg per tree in various experiments. With 125 trees per ha, that suggests that yields of 1,000 kg/ha would be considered low and yields of 5,000 kg/ha high, with 8,000 kg/ha quite high, but theoretically possible. Natural fruit drop amounts to 25% so thinnings of 25% are practiced, and the thinnings could be counted among the residues. The chaff factor of 0.2 accounts for the seed. In Egypt and the Sudan, the trees are pruned back to 40 or 50 leaves. Excess leaves may be pulped or treated as biomass. Midribs are sometimes used in making crates. Annual production of leaves is ca 12–20 per tree per year. Offshoots should be pruned, and may constitute a sizeable residue. Alcohol may be made by fermenting the sap; a tree yielding ca 5 liters toddy per day for 6 to 8 weeks (C.S.I.R., 1948–1976). Alcohol could also be made, of course, from the sugars. Perhaps optimistically, Samarawira estimates a sucrose production potential of 7.2 MT/ha/yr, comparing it to the world average of 6.6 for cane sugar and 5.6 for sugar beet in Europe. Samarawirals optimistic numbers are derived by multiplying the fruit yield potential of 12 MT/ha by 60%, the sucrose percentage of the DM of the mesocarp of the Khalal and early Rutab stages of fruit development. Certainly if these numbers are real, this has energetic implications for the arid tropics when the oil runs out (Samarawira, 1983). To me, it looks as though the date palm should be as productive of biomass as the oil palm in frost free irrigated situations. Oil palm is reported to have an annual productivity of 37 MT/ha/yr in Zaire (Duke, 1981b).

Biotic Factors

Ag Handbook 165 lists the following diseases affecting the date palm: Alternaria sp. (leaf spot), Alternaria citri (brown spot of fruit), Alternaria stemphylioides (fruit spoilage), Aspergillus niger (calyx-end rot), Auerswaldia palmicola (on leaves), Catenularia fuliginea (fruit rot), Ceratostomella radicicola (root rot), Colletotrichum gloeosporioides (on leaves), Diplodia phoenicum (leafstalk rot, shoot blight, fruit rot), Endoconidiophora paradoxa (black scorch, heart bud rot), Fusarium spp. (inflorescence blight, fruit rot), Graphiola phoenicis (leaf spot, false smut), Meliola furcata (black mildew), Meloidogyne spp. (root knot nematodes), Omphalia pigmentata (decline disease), Omphalia tralucida (decline disease), Penicillum roseum (fruit rot), Pestalotia sp. (leaf spot), Phomopsis phoenicola (fruit rot), Phymatotrichum omnivorum (on roots), Pleospora herbarum (fruit rot, mold), and Poria spp. (wood rot). Popenoe (1920) assesses the percent damage caused by some of the major insect pests. Tackholm and Drar give a good account of Egyptian diseases and pests.

References

Complete list of references for Duke, Handbook of Energy Crops
Last update Wednesday, January 7, 1998 by aw