Socotra Pomegranate Tree (Punica protopunica): The Vulnerable Predicament of the "Other Pomegranate"

The French language is the vehicle by which the word pomegranate entered the English language. The Old French word is pomme-grenade. But the Latin language is the ultimate origin of the current English word and the Old French term. In fact, to ancient Roman ways of thinking, the original term required two words: pōmum (“apple”) and grānātus (“seeded,” from Latin grānum,
“grain”).

The seediness of the prized fruit indeed is an unforgettable, hallmark characteristic of pomegranates.

But the word actually may refer to one of two main pomegranates in the world today. One is the expensive, healthy, tasty pomegranate (Punicus granatum), whose devotees cannot wait for the fruit and the juice to become available in stores near them. The other is the Socotran pomegranate (Punica protopunica), whose ecologically vulnerable tree never has fans lining up to pick fruits off the branches or from the ground.

Characteristics of its botanical order:

The Socotran Pomegranate Tree is in  the order Myrtales (Greek: μύρτος, murtos, “myrtle, myrtle tree”), whose general characteristics are the following:

1. Embryonic seed leaves: two in number;

2. Leaves: oppositely paired;

3. Petals: clavate (Latin: clavus, “knot in wood”), or club-like in greater thickness at the tip than at the base;

4. Stipules (Latin: stipula, “straw, stalk”), or basal outgrowths on both sides of the leaf stalk: short;

5. Veins: prominent and strong.

The tree is in the genus Punica, whose name is the feminine form of the Latin adjective punicus. Both the feminine and masculine forms of the Latin adjective literally mean “of or relating to Phoenicia.” The name of the genus therefore honors the Phoenicians, who popularized the fruit’s consumption between the 16th and the 4th centuries B.C.E.

Indeed, according to ancient Greek historian Herodotus ([Greek: Ἡρόδοτος, Hēródotos, “Given to the hero”], c. 484 B.C.E. – c. 425 B.C.E.), the Phoenicians moved to lands along the southeastern Mediterranean from their homeland along the Erythraean Sea (Greek: Ἐρυθρά Θάλασσα, “Red Sea”). The Erythraean Sea is an ancient Greek designation for the combined waters of the Gulf of Persia, the Indian Ocean and the Red Sea. Therefore, the shores of the modern Arabian peninsular Republic of Yemen, which includes as one of its constituent parts the island of Socotra, are the native lands of the Phoenicians.

In fact, punicology is the study of pomegranates. A punicologist is a botanist who specializes in studying pomegranates.

The genus to which the Socotran Pomegranate Tree currently belongs just has two species. One is the species granatum, which is occupied only by the modern pomegranate tree. The other is the species protopunica, which is occupied solely by the Socotran Pomegranate Tree.

The Socotran Pomegranate Tree differs noticeably from the other species:

"In general habit it is not unlike the pomegranate, but its leaves are larger and coarser, and it wants the delicate character of the foliage of  that species. The flowers, too, are somewhat smaller, and their turbinate base is more angular. The fruit is very much less in size." (Sir Balfour, p. 96)

As final and tidy as a scientific classification can look on paper, it can be challenged and changed … or not. Such is the case with the Socotran Pomegranate Tree. For example, Russian scientists Inessa Alexeyevna Shilkina and Gregory Moiseyevich Levin (born January 1933) are dissenting voices regarding pomegranates. They base their arguments upon Socotran Pomegranate Tree wood containing fiber tracheids (Greek: τραχεῖα, tracheia, “windpipe”), which are water conducting cells. They say that this is the tree’s unique characteristic which differentiates it from all the other 10,256 arboreal and botanical varieties of the Myrtales order within which the Socotran Pomegranate Tree currently is classified. They state that this characteristic is not shared even with the modern pomegranate tree. They therefore urge that the Socotran Pomegranate Tree not only be the lone member of its species but also the sole occupant of a new genus, Socotria.

The Socotran Pomegranate Tree grows in central-west Socotra. It is found in moist woodlands on the granite slopes of the Haggeher Mountains, which soar to a maximum elevation of 4,931 feet (1,503) meters, and on Diksam, the island’s limestone plateau, which perches precipitously at 4,986.87 feet (1,520 meters) above sea level. Punica protopunica locates at altitudes between 984 and 3,937 feet (300 and 1,200 meters) above sea level.

The total area which it occupies is estimated at around 38-1/2 square miles (100 square kilometers), or about 1/15 of the island's total area of 1,465.6 square miles (3,796 square kilometers).

Sir Isaac Bayley Balfour FRS FRSE (March 31, 1853-November 30, 1922) is the first known European discoverer of the Socotran Pomegranate Tree. The Scottish botanist discovered the tree during his arboreal and botanical expedition of 1880 to Socotra. He proceeded to describe and name the tree, which intrigued him:

"In Punica protopunica we have a plant which in interest surpasses most of the others in the flora..." (p. xxxvii)

"This is a very distinct and interesting species. . . . A small tree, it grows in abundance over the plateau sloping southwards from the Haghier peaks." (p. 96)

The Socotran Pomegranate Tree matures to a height of 8.20 to 14.76 feet (2.5 to 4.5 meters). It therefore is considered a shrub or small tree. Woody plants less than 30 feet tall (9.14 meters) are called shrubs or small trees. Woody plants over  30 feet (9.14 meters) in height are categorized simply as trees.

But the Socotra Pomegranate Tree actually may assume one of two main shapes. One shape is more horizontal in height and sparser in width. This is the shape of Socotra Pomegranate Trees which grow on the rocky slopes of central Socotra.

The other shape is more vertical in height and width. This is the prostrate shape of Socotra Pomegranate Trees which grow on Diksam, the island's limestone plateau. What with height and width about equal, the tree has the look of a vertically spreading bush.

Bark, branches and trunk:

The bark is reddish brown while the Socotra Pomegranate Tree is young and vigorous. But it fades to a mellow grey as it becomes less fruitful with age.

The tree's branches often have thorns.

Leaves:

The evergreen leaves of the Socotra Pomegranate Tree grow in pairs on opposite sides of the stalk.

Their shape is likely to be elliptical or oblong. But the leaves also may be circular, obovate (Latin: ob-, “against, facing” + ōvātus, “egg-shaped”) or oval. In fact, all five possibilities may be evidenced on one tree and even on one branch.

Each dark green, glossy leaf matures to a length or about 1/25 inches (3 centimeters).

Flowers:

Bright pink, trumpet-shaped flowers appear in December and January and last through the summer. They grow at the ends of the Socotra Pomegranate Tree’s spiny branches. They may show up singly or in floral groups of 2 to 3.

The flower’s crumpled petals call to mind a teardrop when they are obovate, or in a reversed oval shape. They have the look of a heart when they are cordate (Latin: cordi- from cor, “heart” + di-, “like”).

The flowers of the Socotra Pomegranate Tree are considered complete. They have all the parts which are needed for fertilization and pollination to take place. They nevertheless benefit from the frequent visits of honeybees (Apis spp).

Fruits:

The fruits of the Socotra Promegranate Tree vaguely call to mind modified, small tangelos (Citus x tangelo) in their shape. Specifically, they do not lose their floral calyx tube, which is somewhat reminiscent of the tangelo’s nose. They ripen from green to a yellow green which may have muted pink highlights.

A tough skin covers the fruit. The inside of the fruit is made up of spongy tissue, membranes and compartmentalized sacs of pulp and seeds.

Seeds:

There are hundreds of lightweight seeds within each fruit of the Socotran Pomegranate Tree. In fact, 1,000 dry seeds weigh no more than 0.01 pounds (6.81 grams).

Socotran Pomegranate Trees can be cooperative about being cultivated  elsewhere other than on the island of Socotra. But they have certain requirements, from which they will not budge:

1. Temperatures above 60 degrees F (15.55 °C):  This is the preferred lower limit of what the Socotran Pomegranate Tree tolerates in terms of cooler temperatures. In fact, the tree may survive temporary drops to lower temperatures. But it will not be happy. It definitely cannot handle freezing temperatures or frozen ground.

2. Sunlight for about 6 to 8 hours per day, particularly as reflected light inside or from a position of light shade and protection from winds outside when the tree is young;

3. Moisture accumulation of 40 inches (1,000 millimeters) which does not result in pooling or waterlogging, which drains neither too quickly nor too slowly, and which is distributed evenly throughout the year;

4. Humidity no lower than 20% and no greater than 40%;

5. Soils with an alkaline pH level above 7.0 and a calcareous (Latin: calx, “lime, limestone”) or rocky gravel content.

6. Propagation:  In the wild, the Socotran Pomegranate Tree produces seeds which do not germinate. The suspected cause of the lack of regeneration, which is a reason for the tree's vulnerable status on the International Union for Conservation of Nature and Natural Resources (IUCN) Red List of Threatened Species, is the decreased availability of moisture in the air and through the ground. For example, Socotran Pomegranate Tree seed will not germinate if it is dried out from too little moisture or if it is waterlogged from too much.

In cultivation, cutting, grafting and seeding may be options. In fact, Kew Royal Botanic Gardens Herbarium botanist Alan Radcliffe-Smith (1938-August 8, 2007) propagated the Socotran Pomegranate Tree by all three methods. All three methods took, even though cutting and grafting did not result in fruitful varieties.

In terms of the home gardener, seeding or hardwood cuttings are the most convenient and successful means of propagation. Seeding can produce germinated seeds in about 6 to 8 weeks. But seedlings do not come true to type in the quite variable Socotran Pomegranate Tree.

In contrast, cuttings, which come true to type, may be taken any time from late winter to early spring. The cutting length ranges from at least 1/2 inch (1.27 centimeters) in diameter to at least 8 inches (20.32 centimeters) in length. Cuttings should be dusted with rooting hormone on the cut end and planted two-thirds deep in soil.

Either way, it is always a question of respecting Socotran Pomegranate Tree needs for appropriate levels of heat, light and moisture as well as proper rates of drainage.

The Socotran Pomegranate Tree has no currently known use other than an ecological role and an ornamental value as a tree whose foliage and fruit brighten the arid landscape and whose flowers attract honeybees. For example, the tree is not dismembered or felled for construction, drought fodder, or firewood. Neither its foliage nor its fruit is fed to livestock. In fact, islanders refrain from consuming the calcium- and vitamin B-rich fruit other than under circumstances of dire need.

And yet the tree has potential uses. Specifically, the Socotran Pomegranate Tree offers wood which is closely grained, durable, hard and termite resistant. Its bark and roots provide alkaloids and tannins whose presence in other woody plants guarantees their use in traditional and alternative medical treatments. Its flowers, fruits and roots remain untapped sources of dye. Its fruits serve as untested suppliers of jam, jelly and sauce, all three of which generally find their flavor and popularity enhanced by the astringency or bitterness of the main fruity ingredient.

Traditional solution to a modern predicament: An explanation for the disconnect between existence and exploitation can be found in the prescient adjustment of islander culture to island realities. Specifically, the Socotran Pomegranate Tree is vulnerable to the impacts of changing climate conditions and expanding human-made environments on soil health and water availabililty. In such a context, islanders reach the same decision as their insular ancestors: They turn to other activities and give the resource in question a chance to survive.

My special thanks to:

• Talented artists and photographers/concerned organizations who make their fine images available on the Internet;

• Virginia Polytechnic Institute and State University for superior on-campus and on-line resources.

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• Available via Biodiversity Heritage Library at: http://biodiversitylibrary.org/item/80063

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• Available at:  http://www.iucnredlist.org/apps/redlist/details/30404/0

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