Calamus

The holy anointing oil of Exodus 30 has four aromatics, and the third is qaneh bosem, usually translated sweet cane or aromatic reed and usually identified with Acorus calamus, sweet flag. The plant fits: it is a marsh reed with a strongly aromatic rhizome, warm and slightly sharp, and it was traded through the ancient Near East.

The identification is not secure. Some scholars read qaneh bosem as a lemongrass, some as a true cinnamon, and one strand of argument since the 1980s has proposed cannabis on phonetic grounds, which is treated sceptically by most Semitists but keeps recirculating. The atlas records the identification as open.

The plant has an unusually wide independent life. In Ayurveda it is vacha, given for speech and for the mind. Across northern North America the rhizome is chewed as a stimulant and used medicinally by many peoples, and Acorus americanus is a distinct native species rather than an import. European brewers used it before hops, and it flavoured gin and absinthe.

Regulation has caught up with it. The beta-asarone in the diploid Asian varieties is carcinogenic in animal studies, and the United States banned calamus in food in 1968. The North American diploid variety contains essentially none, which the ban does not distinguish.

Acorus calamus is a good example of a species whose distribution is an artefact of human use. It is a wetland plant with an aromatic rhizome, it spreads readily from fragments, and it has been carried and planted for so long that its natural range is difficult to reconstruct. In much of Europe it is an introduction, arriving from Asia in the sixteenth century by way of botanical gardens and escaping from them.

The genus is old and odd. Acorus was long filed with the arums and is now placed in its own family and order, Acorales, at the base of the monocot tree, which makes it one of the earliest diverging lineages of flowering plant still alive. A plant that is used as a village medicine across the whole northern hemisphere is also a phylogenetic relic.

Its uses cluster around the same properties everywhere it goes: chewed for the throat and for alertness, strewn on floors for the smell, added to drink, given for the digestion. Medieval English churches were strewn with rushes that included it, and Ely's were famous enough to be complained about as an extravagance.

The ritual weight is thinner than the medicinal. Outside the Exodus text and the Native American practice, calamus is mostly a useful plant rather than a sacred one, and the atlas records it here because of the anointing oil rather than in spite of it.