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Growing Dates: Phoenix dactylifera

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Overview
Phoenix dactylifera, the true date palm, is a member of Arecaceae, the date palm family. It is one of 13 palms in its Phoenix genus, all of which are called feather palms because of the shape of their fronds. This is the only date palm grown for its edible fruit, and it has hundreds of cultivated varieties throughout the world. The number of cultivars is uncertain because many have different names in different countries and even in different provinces and towns.

Description
Form: Palm.
Lifespan: While this palm may live and be productive for 150 years, its maximum productivity declines after 35 years. Some commercial operations cut down the palm at 40-50 years of age, when it is about 50-65' high.
Leaf retention: Evergreen.
Growth rate: Slow. Medjool palms are the fastest growing cultivar at 12-18" per year.
Mature Size: 100-120' high.
Flowers: Tiny, in large clusters, three sepals and three petals, male are white and female yellow-green. Male and female flowers grow on different plants. Both clustered inflorescences are covered with a hard, fibrous sheath (the spathe) which cracks when pollination is to begin. Female palms are naturally pollinated by wind, and one male palm may be grown for 40-50 females. Hand pollination is performed in commercial production and produces significantly higher yields. However, if fruit thinning is not done after hand pollination, the palm will switch to alternate bearing, heavy one year, light the next.
Bloom: Usually mid to late winter.
Self-fruitful: Can produce fruit without pollination, but unpollinated dates will have no sugar and be considered tasteless and inedible.
Years before fruiting: 3-8, depending on cultivar. They are in full production after 15-20 years. Depending on climate and cultivation practices, a mature Deglet Noor can produce 200-300 pounds of fruit per year while a mature Medjool can produce 150-225 pounds.
Fruit: Fleshy, with a thin skin and a single seed. Each palm produces 5-10 bunches, with each bunch capable of having more than 1000 dates. The fruit go through four stages of ripening from immature green (kimri), to mature full-colored but astringent (khalal), to soft with full size and weight (rutab), and finally, hard, much more dry, and less astringent (tamar). Natural fruit drop may occur twice, at about 25-35 days and 100 days after female spathe cracking.
Months for fruit to ripen: 8-10 months.
Storage after harvest: Up to one year after fully ripened when humidity is under 20% and the fruit are properly packaged. Some dates in each bunch do not ripen past the third stage and must be picked and exposed to heat, but not sun, to finish ripening.
Leaves: Green to blue-green fronds, up to 15' long, 2' wide, slightly curved, v-shaped central stalk with long, narrow, folded leaflets growing along both edges. The life expectancy of a frond is 3-7 years, although some may live longer.
Stems: The trunk has a diamond pattern from cut fronds, can be up to 2' in diameter, and may be wider at the bottom. Each frond stalk has 4-6" long sharp spines along both edges. Commercial growers remove the spines.
Roots: Finely branching roots with no tap root. Roots are normally encouraged to grow out 15' from the trunk in commercial production.
Cultivars of Note:
'Deglet Noor' long, thin, somewhat chewy, moderately sweet. Originated in Algeria. Widely grown in California, grown in Nevada, unsuccessful in Arizona.
'Medjool' large, soft, very sweet. Originated in Morocco. A high quality date. Grown in Arizona and California.
'Black Sphinx' Smaller, sweeter, thinner skin than Medjool. Originated in Phoenix as a mutation of 'Hamlin'. Low crop yield. Ripens during late summer rains which cause mold and rotting.
Wildlife: Does not attract pollinating insects or birds.
Toxic / Danger: No. Sharp spines at the base of each frond may cause severe injury unless removed.
Origin: North Africa or the Middle east. The date palm has been domesticated for at least 8000 years, obscuring its origins.

Cultivation and Uses
USDA hardiness zones: 8b-11.
Chill hours: None.
Heat tolerant: Over 120°F. Needs heat to pollinate and ripen fruit.
Sun: Full sun.
Drought and rain tolerance: Drought tolerant, but needs substantial irrigation to produce a good fruit crop. Summer rain and humidity harm ripening fruit. Medjool is fairly tolerant of summer rain and humidity, Deglet Noor is not.
Water after becoming established: Once a month. Once a week during fruiting. Use a ring dike around trunk for irrigation. Commercial growers irrigate an area 15' in radius around the trunk, often using low overhead sprinklers to better control water distribution.
Soil: Well drained, sandy, 3-5' deep, pH 6.6-7.5 (neutral). Date palms are salt tolerant. The location must not be subject to standing water. Medjool is more tolerant of clay soils than Deglet Noor.
Fertilize: Composted manure, or use a palm fertilizer according to directions on the package.
Mulch: Not needed.
Spacing: 20-40' apart.
Planting: Palm offshoots should be planted between late spring and early summer. Date palms do poorly in containers.
First Year Care: The roots on offshoots must not be allowed to dry out; offshoots should be planted in the field immediately with their fronds tied up for the first year. The new offshoot needs constantly moist, well-draining soil. Protect from wind and cold and provide part shade all day. Palms are slow to establish after planting.
Pollination: Once the hard, fibrous sheath (spathe) has cracked on the male plant, it is tied with a string to hold it together and removed. The spathe is then hung upside down to dry. When dried, the fine pollen powder is sifted into storage jars. The pollen of any Phoenix species, such as that of the Canary Islands palm, can be used to pollinate the true date palm.
When the female spathe begins to crack and open, it is removed to expose the flower strands. Some center strands are discarded to thin the fruit crop and make pollination easier. Pollen-infused cotton balls are inserted at the top center of the flower strands and the strands tied together just below that point. Wind dispenses the pollen to the flowers.
Pruning and fruit management: Two-thirds to three-fourths of the small green dates must be removed. In Medjool date cultivation, green dates are thinned along the strand so that those remaining have more space around them to grow larger and get better air flow. In Deglet Noor cultivation, the bottom two-thirds to three-fourths of all fruiting strands, or some entire strands are cut off. These techniques do not reduce the total weight of the fruit crop. Thinning is necessary to prevent the tree from going into alternate bearing mode, where it has a heavy crop one year and a very light crop the next. Fruit bunches are bagged after thinning to protect them from humidity, rain, sunburn and bird predation.
Cut off flower clusters as soon as they fully open if fruit is not wanted, but be careful not to cut green fronds. Cut off brown and yellow fronds, leaving green fronds to supply energy to the roots. Removing flower clusters provides the palm with more energy to grow additional fronds.
Keep grass and other vegetation at least 6' from the trunk.
Remove offshoots at the base of the trunk unless you want them for growing additional palms, then keep only a few.
Litter: Moderate: flowers, dates, dead fronds.
Propagation: Offshoots, growing from the base of the trunk, are removed when they develop their own roots and possibly flowers, after 3-5 years. Offshoots are clones and true to the parent.
Seed does not breed true, partly because of genetic variability and partly because palms hybridize easily with other palms. There is no way to tell a male seed from a female until the plant has grown for several years and begins to flower. Seedling-derived palms are inferior to offshoots in quantity and quality of fruit production.
Uses: Fruit, ornamental.

Comments
Rain and high humidity can ruin pollinated fruit when it is in the second to fourth stage of ripeness. Enclosing the fruit bunch with a small-hole-perforated bag after thinning may protect it. If rain occurs and the bunch is not bagged, consider harvesting the fruit and exposing it to heat, not sun, possibly in a hot, dark, ventilated shed, to finish ripening over many weeks.



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Phoenix dactylifera



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