With the approach of spring, an air of expectancy descends on the Oasis. It is nearly time for our date palms to blossom. Unlike most fruit trees, date palms are dioecious (Greek for ‘two households’), which means that every date palm is either male or female. In nature, male and female date palms live side by side in almost equal number. In spring, pollen from male palms is dispersed to female palms. By summer these bear fruit containing the seeds of the next generation of palms.
In nature, however, the male palm must rely on the wind or the wings of a bee to carry his pollen to the flowers of nearby females. This is a hit and miss affair (or courtship). As well as the capricious nature of the wind and pollinators, male flowers often open earlier than the female which risks precious pollen being lost. Even once open, female flowers are receptive to male pollen just briefly.
Enter man. To combat the uncertainty of nature and to select for the tastiest fruit, by 3300 BC in Mesopotamia the ancient Sumerians had perfected the art of pollinating date palms by hand.1 Once they realised that one male palm produced enough pollen to fertilise 50-100 females, they replaced most males in their groves with females and took over the act of pollination themselves. This at once brought economies in land use, water, and fertiliser. It ensured the abundant harvests that allowed the world’s first cities to flourish in the ‘cradle of civilisation’ on the Tigris-Euphrates delta.
An ancient Sumerian wandering into a date grove today would feel immediately at home. In most groves, palms are tended just as they were 6000 years ago. The lethal, long thorns on the palm frond are cut off to avoid injury to the pollinator just as the modified leaves (spathes) containing the flower clusters emerge near the crown of the palms. Green at first, spathes turn brown and leathery in the sun and, when the flowers inside are ready, split open, usually by mid-February.
Male spathes are cut down from the tree and their flowers removed. White and star-shaped, these are packed on short sprigs radiating from a central stem like a feather duster. Each flower has six tiny pollen sacs which open within a few hours. We carefully separate the sprigs from the stem and wait for the female flowers open.
Once the female spathe splits, the outer casing is cut away to release its flowers resembling long strands of pearls. A few sprigs of male flowers are inserted in the middle and the bundle tied to keep the flowers together. Time is of the essence as, once the female flowers open, they are receptive to pollen for only a day or two.
The fertilised flower bunches develop rapidly into large clusters of hard green fruit. The clusters are thinned to encourage fruit to grow bigger (the discarded strands making a welcome treat for the goats). As the dates ripen, they are covered in mesh bags to protect them from wasps and birds.
Given the focus on the productivity of the female date palm, it is tempting to view the male simply as a pollen-donor, valued only for the quantity of pollen he produces. However, studies have identified a ‘metaxenia effect’ of male palm pollen having a direct and obvious effect on the size and ripening of the fruit.
In practice, Omani date farmers have always believed that quality of the male pollen has a direct influence on the quality and quantity of fruit produced.2 Some date-producing communities go further, believing that certain male palms are better suited to certain female varieties than others. 3
An intriguing echo of this tradition comes down to us in a story from a fifteenth-century treatise on natural history which relates that a farmer from Arabia, worried about a female date palm that had stopped producing fruit, called in an expert. After climbing the tree and examining her, the expert declared there was nothing physically wrong, but that she was in love with a male date palm a short distance away. “Pollinate her from him only” he advised. Sure enough, after the farmer did so, the female palm resumed her abundant fruiting. 4
Around AD 77, the great natural historian, Pliny the Elder, wrote, “…it is said that in a natural palm grove …many female trees may be seen surrounding a single male with downcast heads and a foliage that seems to be bowing caressingly towards it.”
While this may sound fanciful to a modern mind, through thousands of years of living side by side with the date palm has given man insight into its many mysteries which modern science still strives to define.