How a tree connected Rome, India, and Arabia

The tree does not look like what it has done to the world. 

This is the frankincense tree. It is small — rarely above five meters, often less. It grows out of bare rock on the limestone cliffs of the Dhofar mountains in southern Oman, in conditions that would kill most plants: intense heat, minimal soil, long months of complete aridity broken by the Khareef, the monsoon that rolls inland from the Indian Ocean between June and September and transforms the mountains into a landscape of startling green. Boswellia sacra has evolved to exploit that specific combination — drought stress before the Khareef triggers resin production, which makes the tree economically significant. Scarcity is the mechanism. The tree produces its most valuable substance in response to the conditions that would defeat anything less specifically adapted to them.

Cut the bark with a metal tool in the right season, in the right place, at the right depth, and the resin exudes. It hardens in the air into what the trade calls tears — small translucent lumps ranging from pale yellow to silver-white, depending on the grade and the elevation of the tree. The highest grade, Hojari, comes from trees growing on the mountain slopes above Salalah. The lowest, Sha’abi, comes from trees in the wadis and coastal plains. Between them sit half a dozen intermediate grades, each with a specific character, a specific price, and a specific history of application.

The frankincense from these trees has been burned in the Temple of Baal in Babylon, used by Cleopatra’s physicians, and traded across a network that was, for five centuries, the most significant commercial infrastructure in the ancient world. It is still being harvested on the same cliffs. The trees do not know this.

THE GEOGRAPHY THAT MADE THE TRADE POSSIBLE

The Dhofar mountains rise abruptly from the Arabian Sea coastline to approximately 2,100 meters above sea level. The southward-facing slopes catch the Khareef; the northward slopes face the Empty Quarter, the largest continuous sand desert in the world. The Boswellia sacra tree grows on the escarpment between them — in the wadis and on the cliff faces, where the specific combination of moisture, heat, and minimal competition from other plant life provides the conditions it requires.

The most important single site is Wadi Dawkah, a protected valley 45 minutes’ drive from Salalah, where thousands of frankincense trees have been growing for centuries. In 2000, Wadi Dawkah was designated part of the Land of Frankincense UNESCO World Heritage Site — one of four sites that collectively document the full extent of the ancient trade, from the tree groves through the caravan cities to the port at Khor Rori, where the resin was loaded onto ships for the journey to Mesopotamia, Egypt, and India.

The trees at Wadi Dawkah are not managed in any conventional agricultural sense. They are tended. The harvesters — predominantly from the Dhofari tribes whose families have worked the same groves for generations — know each tree individually, know its yield history, know which cuts are sustainable and which will damage it. The knowledge is not written down. It is demonstrated, from father to child, across the face of the same cliff.

The Boswellia sacra tree is listed as Near Threatened on the IUCN Red List. The primary threats are not deforestation but over-tapping: harvesters making too many cuts, too deep, too frequently, in response to global demand that has grown faster than sustainable harvesting can support. A global wellness market is pressuring the tree that survived Babylon and Rome, which it has never heard of.

WHAT THE TRADE ROUTE BUILT

The Incense Trade Route thrived between the 3rd century BCE and the 2nd century CE. Known today as the Frankincense Route, it moved one of the ancient world’s most valuable commodities from southern Arabia to the Mediterranean, Mesopotamia, Persia, and India. It was not a single road but a system of routes connecting Dhofar and Yemen to the Nile Valley, Mesopotamia, Persia, Greece, and Rome — making use of more than two dozen Arabian communities, caravanserai, forts, and the sophisticated irrigation systems that allowed caravan cities to exist in terrain that should not have been able to support permanent settlement.

The Nabataeans were the system’s most significant operators. Based in Petra in what is now southern Jordan, they controlled the northern termini of the frankincense routes and grew wealthy by taxing every caravan that passed through their territory. The tomb facades at Petra, carved from rose-red sandstone and decorated with Greek and Roman architectural details, are material evidence of what frankincense money built. A city of extraordinary architectural ambition, in a desert canyon, funded by a tax on a tree growing 2,000 kilometers to the south.

The route east went from Dhofar along the Arabian Gulf coast to Mesopotamia, where Gerrhean merchants transferred the cargo to the networks connecting it to Babylon and, eventually, to the Silk Road. The Temple of Baal in Babylon burned an estimated 2.5 tons of frankincense per year, according to ancient records. Pliny the Elder recorded that Emperor Nero, upon the death of his wife, Poppaea, burned an entire year’s worth of frankincense from Arabia at her funeral. These are not figures of speech. They are the scale of an economy.

The ancient port of Khor Rori — known as Sumhuram in antiquity — lies 40 kilometers east of Salalah on the Omani coast, at the mouth of Wadi Darbat. Active from the 4th century BCE to the 5th century CE, it was the primary maritime hub for the frankincense trade, the point where overland caravans ended, and ships began. The ruins are accessible today: stone walls, the remains of a temple and a palace, the harbor silted over but still visible from the ridge above. It is a place that requires effort to reach and rewards the effort with the specific quality of silence that belongs to places that were once very loud.

THE GRADES AND WHAT THEY TELL YOU

The resin is not a single substance. It is a spectrum, and the spectrum is geographical.

Hojari, the highest grade, comes from trees growing on the mountain slopes of Dhofar at an altitude. Its tears are large, pale, and translucent — the texture of old ivory, the color of diluted honey. When burned, it produces a clean white smoke and a scent that is simultaneously resinous and fresh, with a citrus quality that distinguishes it from resin produced elsewhere. Hojari was the grade that reached Rome. It was the grade that the Magi brought. Whether the attribution is literal or not, the detail is accurate: this specific resin, from this specific geography, was the most valued aromatic substance in the ancient world.

Najdi, harvested from trees growing on the plateau above the mountains, produces a slightly darker tear with a warmer, more earthy character. Sha’abi, from the coastal wadis, is the most abundant and the least expensive: larger tears, more yellow, a heavier scent. A Dhofari trader handling the three grades simultaneously can identify each by touch, by smell, and by the way the tear breaks when pressed between the fingers. The knowledge is not specialist knowledge in Dhofar. It is the general literacy of a society that has lived with this tree for three thousand years.

The grading system is being formalized as the commercial market grows. Amouage, the Omani luxury fragrance house, signed a partnership with Oman’s Ministry of Heritage and Tourism in 2022 to develop sustainable harvesting practices at Wadi Dawkah, investing in the local workforce and the long-term health of the grove. The house uses Boswellia sacra as a central ingredient in its perfumes. It is, in a direct line, doing what the ancient trade route did: connecting a tree on a Dhofari cliff to markets in cities around the world, through a system of relationships, knowledge, and commerce that the tree itself knows nothing about.

WHAT SURVIVES

The caravan cities are ruins. The ships that left Khor Rori have been gone for fifteen centuries. The Nabataean trading empire that taxed the route from Petra was absorbed by Rome in 106 CE and exists now only in its stone facades and the memory of a city that should not have been there.

What survives is the tree and the knowledge of how to tend it.

In the Dhofar mountains, the families who have harvested the same groves for generations continue to do so. The tools are the same — a metal implement called a mingaf, used to make the specific incisions that release the resin without killing the branch. The reading of the tree — knowing when it has recovered from the previous harvest, knowing which incision sites are productive and which are stressed, knowing the difference between a tree that can sustain three tapping seasons per year and one that can sustain one — is the same knowledge that was operational when Sumhuram was a working port.

The threat is real. Boswellia sacra is listed as Near Threatened on the Red List, with threats including habitat destruction, insect infestation, overgrazing, particularly by camels, and over-tapping for trade. The global wellness market’s rediscovery of frankincense as a therapeutic ingredient has driven demand faster than sustainable harvesting can keep pace with. A conservation study published in August 2025 confirmed complex threats and population patterns across the Omani groves, with the picture varying significantly between sites. The trees at Wadi Dawkah, under UNESCO protection and formal management, are in better condition than those in the unmanaged wadis.

Neal’s Yard Remedies has been running a nursery to cultivate Boswellia sacra seedlings in partnership with the Environment Society of Oman since 2017, distributing approximately 1,000 seedlings per year to local communities as a conservation measure. This is not a solution to a structural problem. It is a holding action against the speed at which the problem is developing.

WHAT THE VISITOR FINDS

Salalah is a two-hour flight from Dubai or Muscat. The Dhofar mountains are green during the Khareef from June to September — the specific Omani version of a cool, misty highland summer that draws visitors from the Gulf who have not seen clouds in months. Outside the Khareef, the mountains are arid, the light is harsh, and the landscape is closer to what it looked like when the caravans moved through it.

Wadi Dawkah is open to visitors and requires no permit. The grove of Boswellia sacra trees is signposted from the main road between Salalah and the Empty Quarter. Walk into the wadi in the early morning, before the heat has fully arrived, and the trees are immediately legible as the specific objects they are: small, gnarled, with peeling, papery bark and branches that produce, from each point of incision, a small amber bead of resin. Pick one up from the ground — fallen tears are everywhere — and hold it. The scent is faint until it warms in the hand. Then it is unmistakable.

The ruins at Khor Rori are 40 kilometers east of Salalah on the coast road. The site is UNESCO-protected and has a small visitor center. The harbor entrance, where frankincense-laden ships once cleared for Mesopotamia, is visible from the ruins above. Allow two hours. The drive back along the Dhofar coast road at sunset, with the mountains inland and the Arabian Sea to the right, is the specific geography that made frankincense trade possible: the proximity of the tree groves to deep-water anchorages, the relationship between the mountains and the sea that no other frankincense-producing region in the world shares at this scale.

The Salalah souqs sell frankincense in every grade, including Hojari, at prices that make clear the distance between what the grove receives and what the market charges. Buy the Hojari. Burn it on a small charcoal disk. The scent that fills the room is the scent that filled the Temple of Baal in Babylon, the scent that Nero burned at his wife’s funeral, the scent that the Magi carried across a desert that has not changed as much as the cities they were heading toward.

The tree does not know any of this. It simply produces its resin in the mountains above the Arabian Sea in the specific conditions that make it possible. It has been doing this for longer than most of what the resin paid for has survived. It will still be doing it if the harvesters, the conservationists, and the market can find a way to let it, long after the current economy it serves has been replaced by whatever comes next.