Frankincense
Boswellia sacra
Frankincense begins in landscapes where trees seem almost impossible. Across the arid mountains and rocky escarpments of southern Arabia, Boswellia sacra can grow from cracks in limestone with barely enough soil to cover its roots. The trees tend to look as though the landscape has had a hand in shaping them. Trunks swell and twist, roots travel over exposed rock before finding a fracture, and papery bark peels away in thin layers.
Cut that bark and something quite different appears. A milky liquid gathers around the wound, then slowly hardens in the dry air. By the time it reaches a jar, it's almost unrecognisable as something that once seeped from a living tree. These hardened tears are frankincense, and they've been travelling far beyond the places where they formed for thousands of years.
Classification
Kingdom: Plantae
Family: Burseraceae
Genus: Boswellia
Species: Boswellia sacra
Common Names: Frankincense, Olibanum, Frankincense Tree
Where Stone Gives Way to Trees
Boswellia sacra is native to the southern Arabian Peninsula, particularly Oman and Yemen, and also occurs in the Horn of Africa. It grows across dry valleys, exposed slopes and rocky mountain terrain where rainfall is scarce and soil can amount to little more than a pocket caught between stones.
Some trees cling directly to steep limestone faces. Roots follow cracks where seasonal rain, runoff and moisture can collect, while older trunks may become swollen and deeply contorted around the space available to them. During severe dry periods, the tree can shed its leaves and slow its growth.
Frankincense doesn't come from B. sacra alone. Several Boswellia species grow across northeastern Africa, Arabia and India, and their resins enter trade under the same broad name. A packet marked simply frankincense can therefore conceal quite a lot about where it actually began.
A Tree with Paper Bark
Frankincense is a relatively small deciduous tree, generally reaching around two to eight metres. Its pale grey to brown bark peels naturally in thin, papery layers, while clusters of compound leaves gather towards the ends of twisting branches during active growth. Small cream white flowers appear in loose clusters before giving way to seed capsules.
Beneath the bark are ducts containing the material for which the tree is famous. Damage the surface and a sticky white liquid begins to gather. Fresh from the tree, it bears little resemblance to the hard pieces eventually traded as incense.
Left exposed to the air, it gradually firms into rounded droplets and irregular tears. Some dry cloudy cream or pale yellow. Others take on warmer amber tones, and particularly attractive material can carry a faint greenish cast. Even within one harvest, the pieces aren't necessarily uniform.
Tears from the Tree
Harvesting begins with deliberately wounding the bark. Shallow cuts are made and the milky material that emerges is allowed to remain on the tree while it hardens. The dried resin can then be collected, with trees sometimes tapped several times over the course of a season.
Those cuts need some restraint. Too many wounds, cuts made too deeply or repeated heavy harvesting can affect a tree's growth and reproduction. For a species already dealing with drought, grazing and difficult growing conditions, how frankincense is collected matters just as much as how much can be taken.
Flowering follows its own schedule, influenced by rainfall, temperature and locality. When conditions suit, the small blossoms attract insects including bees and flies. In landscapes where vegetation can be sparse, a flush of leaves and flowers after rain makes the tree look rather different from the bare, resin producing form most familiar through photographs.
From Milky Resin to Glassy Tears
Frankincense is often called a resin, which is useful shorthand but doesn't quite describe what's in the jar. More precisely, it's an oleo-gum-resin, containing resinous compounds alongside water soluble gums and aromatic oils.
The terminology is more cumbersome than the material itself. Fresh frankincense is sticky and milky. Dry it and the same material becomes hard enough for the tears to knock against one another like small stones. Apply heat and it changes character again, softening as its aromatic components are released.
Different frankincense resins don't behave or smell identically either. Boswellia sacra, B. papyrifera, B. frereana and B. serrata are among the species encountered in trade. Species, locality, growing conditions and harvest can all contribute to differences in fragrance, colour and chemical composition. Frankincense is a useful name, but it's a surprisingly large umbrella.
Following the Incense Road
People have been collecting and trading frankincense for thousands of years. Resin travelled north through Arabia along overland routes and left producing regions through coastal ports, eventually reaching communities far removed from the trees themselves.
It appears in ancient Egyptian, Greek, Roman and Jewish contexts, and later became important within Christian and Islamic traditions as well. It was burned ceremonially, incorporated into perfumes and aromatic preparations, and used within traditional botanical practices. Those uses weren't identical simply because the material was the same. Frankincense accumulated different meanings as it moved between places, religions and periods.
The better documented Mediterranean markets are only one end of that history. Harvesting began with communities living much closer to Boswellia country, and the resin had already passed through many hands before arriving in distant temples, homes and marketplaces.
Its journey hasn't really ended. Frankincense is still burned in homes and places of worship today.
What's in a Name?
Even frankincense has travelled.
The English word came through Old French, with the name referring to high quality or pure incense rather than identifying one particular Boswellia species. Olibanum, another name still encountered for the resin, followed a different linguistic route.
That history makes modern labels slightly deceptive in their simplicity. Two jars can both say frankincense while containing resin from different species, landscapes and harvesting traditions. When the botanical identity is known, keeping it attached to the material preserves a piece of information that the common name can't.
In the Apotheca
Frankincense can be surprisingly mineral like once it's dry. The tears are hard and irregular, with cloudy interiors and thinner edges that become translucent when held towards the light. Tip a few into a glass jar and they sound more like little stones than something harvested from beneath tree bark.
Then heat brings the tree back into the picture. The tears soften, aromatic compounds begin to release, and a material that had become almost inert in the hand produces the fragrance responsible for much of its extraordinary travelling history.
That's part of what makes the species name worth retaining whenever it's known. Boswellia sacra takes frankincense back from a familiar jar of incense to a particular living tree, growing in places where there sometimes seems to be barely enough ground for a tree at all.
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