Everything you need to know about cultivating date palm! Learn about: 1. Botany of Date Palm Plant 2. Origin of Date Palm 3. Climate and Soil 4. Orchard Cultural Practices 5. Propagation Techniques 6. Planting Operation 7. Flowering and Fruiting 8. Pruning 9. Harvesting and Handling.
Botany of Date Palm Plant:
The cultivated date palm is botanically known as Phoenix dactylifera L. and belongs to the family Palmae. The genus Phoenix is distinguished from other genera of pinnate leaved palms by the upward and lengthwise folding of the pinnae and the peculiarly furrowed seeds. About 12 species of genus Phoenix are identified which are native to tropical or subtropical parts of Africa and Southern Asia. In India, another species Phoenix sylvestris (L.) Roxb is cultivated as a rich source of sugar. Phoenix dactylifera is distinguished from this species by the production of-off shoots or suckers.
All species are dioecious, male (staminate) and female (pistillate) flowers are produced in clusters on separate palms in the axils of leaves of the previous year’s growth. The inflorescence or flower cluster is a branched spadix and is enclosed before maturity in a protecting sheath or spathe. Leaves of date palm are 3 to 6 metres long and have a normal life of 3-7 years. Old and dead leaves are not shed but they are removed under cultivation. Phoenix dactylifera has 36 chromosomes (n=18, 2n=36).
Origin of Date Palm:
The date (Phoenix dactylifera) is one of the oldest fruits and was known to man many thousand years before Christ. It originated in the Mesopotamian basin in Arabia where the culture of mankind originated. The date-palm is a monocotyledonous plant like the banana. Therefore, its stem is un-branched and it does not grow in thickness with age.
Dried dates are one of the most nourishing foods in the world. They contain about 70 per cent sugars, 2 per cent protein, 2.5 per cent fats and some minerals. One kilogram of fully ripe fresh date fruits provide approximately 3150 calories being very rich in carbohydrates.
It is the staple food of the Arabs. Large quantities of dates are imported by India from the Arabian countries. Wild date-palms are seen growing even upto an altitude of 1500 metres. Of course, they do not fruit at this altitude every year. A species, Phoenix Silvestris, with inferior, but edible fruits is native to India and large clusters of these palms are found naturally occurring along streams, etc., all over the country.
A raw sugar and a fermented drink today are prepared from the sap of this palm. The cultivated date- palm is believed to have originated from this species. It is curious that in spite of all this, dates are not cultivated commercially in India. The reason for this is that it ripens in India in July when the monsoon rains have started. The fruits, therefore, rot.
Fully ripe fruits known as ‘Pind-Khajoor’ are eaten for relief in constipation and anaemia. Fruits having little or no astringency are also eaten at doka (hard ripe) stage. Full doka fruits are boiled and dehydrated to prepare dry dates (chhuhara).
Date palm trees are found growing in Kachchha district of Gujarat and are mostly seedlings. Western districts of Rajasthan, such as Jaisalmer, Barmer, Bikaner and Jodhpur being extremely dry have the highest potential for its cultivation. Nagaur, Churu and Sri Ganganagar districts and some parts of Sirsa and Sikar and parts of Saurashtra also have the potential for date palm cultivation.
The date-palm is a fruit of the deserts of the Middle East. It is said that it likes to have its head in fire and its feet iii water. This is undoubtedly an over statement. However, it needs a great deal of heat for ripening and also needs irrigation. It is very deep-rooted and can draw moisture from great depths of the sub-soil. It can tolerate pH 8 to 10 and alkalinity upto 3-4 per cent in the soil. However for normal root activity the alkalinity should not be more than 1 per cent.
An interesting thing about the date-palm is that there are male palms and female palms. A 10 per cent population of males is necessary for good fruiting. Natural pollination takes place by wind and insects. The Arabs often insert a few strands of flowers from the male trees into the female flowering clusters. The palms for planting have to be of a known sex and are propagated by removing the suckers (off-shoots) along with their roots from the base of the mother-palms.
The date varieties such as Barhee, Halawy, Khalas and Khunezi have a little or no astringency and thus suitable for eating raw. Varieties such as Medjool, Zahidi, Shamran and Khadrawy are astringent at ‘doka’ stage and can be used to prepare dry dates (chhuhara) and soft dates (pind khajoor)
Date palm bears for 40 to 50 years. A planting distance of 8 m apart facilitates inter cultural operations and proper growth of the plants.
On irrigation 15 days before flowering is essential and afterwards moisture is to be retained for proper fruit set, development and ripening. Water deficit may cause pre- harvest fruit drop. Mulching with locally available weed ‘bui’ (Aerva persica) or black alkathene has been found beneficial.
Fully grown date palms should be given 20 to 40 kg FYM during September-December, beside, 0.5 to 1.0 kg each of nitrogen and phosphorus and 0.25 to 0.50 kg of potash. Total quantity of phosphorus and potash and half the dose of nitrogen should be given three weeks before flowering and the remaining dose of nitrogen during March-April.
Climate and Soil Required for Date Palm Cultivation:
The date palm as a tree flourishes well under varied sets of climate. However, for proper maturity of fruit, the date requires prolonged summer heat without
rain or high humidity during the ripening period. A light shower with prolonged periods of cloudy weather and high humidity may cause more damage than a heavy rain followed by clear weather and drying winds. The mean temperature between the period of flowering and ripening of the fruit should be above 21 °C rising to 27°C or higher for at least one month. For successful fruit maturation, nearly 3000 heat units are required. The heat units available in most of the north-western districts of India, counted from the time of flowering, i.e. end February to July, and indicate that these are suitable for date palm cultivation.
It is a general quotation about date palm that their heads in fire and feet in water are essentialities for successful cultivation. Taking into this consideration, parts of Rajasthan extending from Sri Ganganagar to Anupgarh, Jaisalmer and Barmer and Kutch district of Gujarat will be suitable for date cultivation. The climate of Abohar (Punjab) should be considered marginal because of rainfall (30 cm) and high humidity at the time of ripening (July-August) being the limiting factor.
In Mediterranean region no rain occurs during February to September and thus its fruit matures up to pind or tamar stage in about 180 days. In India, no such location is available which could meet this requirement although fairly dry conditions are available in northwestern India. In different parts of India, fruit development period is cut short to 122-170 days and the fruit yet not full mature is harvested early before rains to avoid heavy fruit spoilage.
The date palm can be grown in soils containing more alkali or salts. It can tolerate such condition better than many other fruit plants. In view of the large investment required to bring a date garden into bearing and maintain it on profitable production, sandy loam soil, 2 or 3 metres deep with good water holding capacity and drainage is most desirable. Date palm can tolerate high soil salinity. In the soil having 4 per cent salt concentration, dates can survive well provided the root system does not come in contact with a stratum of soil where the sodictiy is more than 1 per cent.
Orchard Cultural Practices for Cultivating Date Palm:
i. Irrigation:
There is a proverb for date irrigation, that it should have its head in fire and feet in water. Date palm is known as drought resistant fruit tree and is able to survive for long periods without irrigation. However, continuous drought condition retards the growth of the plant. If water is available, date palm used it lavishly. Date palm is highly tolerant to excessive irrigation and floods. Continuous stagnation of water or waterlogged conditions are injurious for its growth. To maintain maximum growth, the root zone up to 2-3 m should be kept moist and not allowed to dry. Light but frequent irrigation should be given after planting.
The full grown trees on the lighter soils are usually irrigated 7 to 10 days during midsummer and every 15 to 30 days during winter. Such soils require 2.75 to 3.75 acre-meters of water per year and 30 to 45 acre-centimeters per month is needed during summer. On heavy soils, half the amount may be enough. Each irrigation of 10-15 acre-centimeters is usually sufficient. Irrigation is withheld when ripening starts to facilitate harvesting, hasten fruit ripening and to reduce fruit drop caused by high humidity.
ii. Intercropping:
Intercropping in date palm with suitable crops bring good income and also improves the fertility of the soil. During the first few years, intercropping can be practised with no shortage of irrigation. Intercrops such as gram, peas, mash, moong, moth, senji and lentil can be sown during summer. Intercropping of some vegetables in plantation located near the cities, can be practised if, sufficient irrigation and manuring facilities are available. The filler trees like grapes can be tried with good success.
iii. Manuring and Fertilization:
Generally the farmers do not apply manure to the date palm. The trees certainly respond to manuring as indicated by increased vigour and growth. The results of studies conducted at Abohar shows that 25 to 50 kg of farmyard manure and 1 to 2 kg ammonium sulphate per palm should be added. The quantities may be reduced if some leguminous crop has been grown in the date palm. Farmyard manure is applied during December-January. The nitrogen dose should be given a fortnight before flowering i.e. in the first week of February.
To get better yield a full grown date palm tree should be given 20-40 kg FYM, 500-1000 g N, 250 – 500 g P2O5 and K2O each annually. Farmyard manure should be applied after monsoon in September to December. The whole quantity of phosphorus and potassium and 60 per cent nitrogen should be given three weeks before flowering. The remaining 40 per cent nitrogen should be applied during fruit development period in March – April.
Propagation Techniques for Date Palm:
Dates can be grown either from seeds or from suckers (offshoots). When grown from seeds, approximately half of the palm will be male and produce only pollen. Its sex will be known only when it comes into flowering after four or five years. In this case, most of the female plants are inferior (not true-to-type) to the mother palm. For breeding purpose, propagation through seed provides an ideal material, or sometimes seedling palm appears outstanding and then this can be further propagated from offshoots.
The date palms are always propagated through suckers (offshoots) for commercial plantation. The suckers usually arise near the ground around the trunk. The offshoots arising at a higher level from the ground on tree trunk and with no roots give very poor survival. These are separated from the mother palms during March or August-September. The leaves are trimmed off 4-5 days before their detachment.
The inner leaves should be cut back by one-half and the outer ones by two-thirds’. The tender young unopened leaves near the central bud and parts of the bare stalks of the old leaves necessary to protect it, should be kept on the offshoot. The outer whirl of leaves may be fastened to afford protection from heat and cold to the central bud also facilitate detachment and transport.
The suckers weighing approximately 25 to 30 kg and are well rooted should be removed. Expose the point of detachment and set a chisel (12 cm wide and 19 cm long) sharpened at the face and welded to a 150 cm long handle of 4 cm diameter. Drive in the chisel by hammering at the other end. It is very important that no injury is caused to the mother palm. Cut surface should be coated with some suitable material immediately and earthed up.
Date palm is usually propagated through its offshoots which are a slow and laborious task due to limited number of offshoots produced during its life cycle. Mass production of date palm plants with tissue culture is possible to produce uniform date plants with proliferation but no callus formation or through somatic embryogenesis from a proliferating callus. Tissue culture raised plants yields the highest quality of dates. This technique provides best quality planting material i.e. true to type, healthy and disease free plants.
Planting Operation for Date Palm Cultivation:
The offshoots are planted 6 to 7 metres apart in the already prepared pits of 1 x 1 x 1 m size immediately after detachment. In this way 202 to 275 plants/hectare will be accommodated. If transported from long distance, the offshoot may be kept in the nursery for one season. The maximum diameter should be in level with the soil and top straight. The soil around the offshoots should be pressed firmly. The field is irrigated immediately after planting. Thereafter, frequent light irrigations are given to keep the soil always moist. At Abohar, the offshoots removed in March survived better in direct field planting than those removed in August-September. However, the separation could be done both in February-March and August-September.
The date palm plantation can be made at 8m x 8m accommodate 156 plants per hectare. In certain areas date palm is also planted at 6m x 6m having 275 plants per hectare.
Flowering and Fruiting in Date Palm Trees:
In date palm, male and female flowers are borne on separate trees being a dioecious plant. Therefore, hand pollination is necessary for production of commercial crop. A female palm usually carries 6 to 12 clusters but the actual number may vary according to the variety and season. A cluster may carry 50-100 strands with 16-30 set fruits on each. The female flowers are pollinated as and when they emerge out of the spathe. This is accomplished by smearing the flower buds with cotton plug dusted with pollen grains and then placing 1 to 3 strands of freshly opened male inflorescence in an inverted position into the female inflorescence.
A twine or a thread pulled from the leaflet is tied with a slipknot around the pollinated cluster about 10 cm from the outer end to hold the male flowers in place. As the cluster develops, the knot slips to leave the cluster open. To avoid re-visits, female spathe about to rupture is cracked open and pollinated. It has been observed that one male palm is enough for about 20 females. If pollen is in short supply, it may be mixed with talc. If the time of opening of male and female spathes does not synchronize, the pollen can be stored dry at room temperature till the completion of pollination.
The date-palm fruit can be divided into four stages on the basis of fruit development and ripening. The Arabic names for these four stages are Kimri, Khalal, Rutab and Tamar. In Punjab these stages are termed as gandora, doka, dang and pind, respectively. Kimri or gandora is a stage when the fruit has grown a little and attains a clear apple green colour. The second stage Khalal or doka is marked by the turning of the colour of the fruit skin from green to yellow to chrome or to yellow, finally spotted with having characteristic of its variety. In this stage, the fruit has attained the full size.
The third stage known as Rutab or dang characterized by the date becoming more or less translucent and softening starts from distal end by darkening of the skin from yellow, chrome or scarlet to brown or to nearly black. The final stage in the ripening of date is called Tamar or pind, when the fruits get fully mature and has lost much of its water, enough to make the sugar to water proportion sufficient high to prevent fermentation. This stage is equivalent to that of raisin in the grape.
Pruning of Date Palm:
One hundred leaves should be retained on the tree for good fruiting. The pruning of leaves is done during January-February before the emergence of flowering spathes. At this time, the leaf stalks adjoining crown and the emerging spathes should be dehorned to facilitate operations such as pollination, bending, harvesting etc. The leaf stalk should be removed close to the trunk to provide smooth trunk surface.
False smut or Graphiola leaf spot (Graphiola phoericis) is most common disease of date palm in humid season. Brown spots appear on both side of leaves followed with drying of leaves. Spray of copper oxychloride (2 g/litre water) or Bordeaux mixture (4:4:50) controls it. Fruit rotting occurs due to poor air circulation inside the bunches and heavy rains at the time of ripening.
Bunch thinning and sulphur dust checks the incidence. The damage caused by termites is controlled with application of 2-3 ml chloripyriphos in each basin with irrigation. Birds damage the fruits at doka, dang and pind stages. Birds scaring, covering the fruits with perforated polythene bags or nylon nets etc. reduces the damage.
Harvesting and Handling of Date Palms:
Harvesting of dates generally depends upon the weather conditions. The rain and high humidity in the atmosphere at the ripening time is a limiting factor in its cultivation. When the climate is favourable, it is preferable to leave the fruit of most varieties on the palm until it reaches the stage of maturity at which it is to be consumed or stored. The changes associated with ripening and the period during which the fruit may be consumed extend from the peak of the khalal stage, when the fruit has its most intense red or yellow colour and maximum weight, to the final tamar stage, when it has lost the greater part of its moisture content and will keep without special attention to storage.
Most of the people like to eat the fruit in khalal stage. At least two varieties of dates-Hillawi and Barhee, are liked most for eating in khalal stage. Dates are hand-picked at the stage of maturity. All the dates in the same bunch do not ripen at the same time; it has been the practice to make several pickings to harvest the fruit during a season. Sometimes, when the season is favourable and more than 70 per cent fruit is ripe, the entire bunch is harvested.
The research conducted on curing of dates at Abohar have revealed that the rain and high humidity in the atmosphere at the time of ripening (July and August) do not allow the ripening process on the tree to proceed satisfactorily beyond doka stage. If the fruit is retained on the tree, there is checking, splitting and rotting. High humidity and rainfall also cause the fruit to drop. Therefore, the crop has to be harvested at doka stage. Though in comparatively drier seasons partial crop on some trees may become dang (mellow and soft) but the quantity of such fruit is limited. The berries are removed and graded manually on the basis of size and colour.
At Abohar (Punjab) a technique has developed to transform satisfactorily the date fruit at doka stage into dry dates (Chhuhara) of good quality. At least four varieties Hillawi, Khadrawi, Shamran and Medjool have yielded very good product. Chhuhara obtained from Medjool, which is a large-sized variety, compare very well with the high quality Chhuhara imported from Middle East counties. The technique developed involves immersion of fruit at doka stage in boiling water for 6 to 8 minutes and then drying either in temperature-controlled oven (air-circulation type) for 80 to 120 hours at 48 to 50°C or in the sun for 10-15 days if weather is dry. Thus, an average of 45 per cent fruit product is obtained.
Fruits at advanced doka stage or when they attain one-fourth, one-half or full dang (the berries become mellow and soft starting from the distal end) can be converted into soft dates (khazoor) of good quality by drying either in the oven at 40°C or in the sun. Thus, for soft dates, only drying the berries at partial or full dang stage is required with no other treatment and this way a final product of soft Khazoor ranging from 50-60 per cent is obtained.
Hillawi and Barhee yielded 50-100 kg fruit per palm at doka stage. The average yield from Khadrawi and Shamran is obtained 40-70 kg fruit per palm. The yield from Medjool palm is upto 50 kg but its fruits are very large in size.
Artificial ripening of fruit at doka stage to transform it into dang stage was also attempted at Abohar. For these studies, berries were treated with 0.5 per cent to 2.0 per cent common salt (sodium chloride) and similar concentrations of acetic acid in combination with 1.0 per cent salt. The fruits to be treated with salt were spread on polythene sheet and requisite quantity of salt was applied by rubbing and smearing uniformly on the berries. The fruits which were given acetic acid plus salt treatments were first dipped in solutions of desired acetic acid concentrations for 2 minutes followed by salt application by the method described above. Each treated lot was packed into wooden boxes lined with old newspapers and packed in laboratory at room temperature.
The boxes were opened after 24 hours. From these studies, it was found that with 2 per cent salt, 60 to 70 per cent of the doka fruit were transformed into dang. However, the dang obtained by this treatment was not as good in taste as that of naturally ripened on the tree, but still it was edible and generally acceptable on account of its having lost the astringency. But such product cannot be stored more than 24 hours and, as such, should be consumed to as early as possible.
Low energy X-ray irradiation can be used as a potential commercial treatment for retaining the quality and ensuring the safety of dates.
Storage:
The shelf life of fresh dates can be enhanced for two weeks in cold storage (5-7°C temp, and 85-90% RH). Fresh dates at Khalal stage can be stored up to two months at 0-1 °C. Dried dates (Chhuharas) can be stored for one year at ambient conditions after packing in gunny bags.