# Sweet flag (Acorus calamus)

**Calamo aromatico**

**Known today as.** *Acorus calamus*.

Kind: Plant  
Toxic: yes

> **Caution.** 

## What did Canale use it for?

In the oil; the “calamus” of Scripture’s anointing oil (ch. 9; Treatise Two).

## What does modern science say?

Most strains contain beta-asarone, which causes cancer in laboratory animals; its internal use is now restricted, and the United States bans calamus in food.

## Pharmacognosy and toxicology

- **beta-asarone**: up to 80 per cent of the oil in the Asian tetraploid plants
- **alpha-asarone**: 

**Mechanism.** -Asarone is genotoxic and caused tumours of the duodenum in rats; it also has sedative and anticonvulsant actions in animals, the basis of the Ayurvedic use.

**Dose.** Chronic; the European limit for -asarone in foods and drinks is 0.1 mg per kilogram.

**Standing.** Forbidden as a food additive in the United States since 1968; the European diploid plant, nearly free of -asarone, is permitted in bitters.

## What lore surrounds it?

Folkard: “This aromatic Reed, or Sweet Flag, is absurdly said to have been called Acorus, from the Greek koré, pupil, because it was esteemed good for diseases of the eye.” The sacred oil of the Jews, “the ‘oil of holy ointment’—used to anoint the tabernacle, the ark of the testimony, the altar of burnt offerings, the altar of incense, the candlesticks, and all the sacred vessels, has the oil of Acorus as one of its ingredients. It is the ‘Sweet Calamus’ mentioned in Exodus xxx.” Astrologers made it “a plant of the Moon.”

## What did the older authorities say?

**Pliny.** Says the scented calamus of Arabia is common to India and Syria, the Syrian best of all, growing in a valley near a lake between Mount Lebanon and a lesser hill, whose marshes dry up every summer; it went into the oldest unguents with myrtle, cypress, and mastic, and into oil of roses, and Plautus’s Persian has calamus added to the myrrh-wine of the old Romans.

## Sources

- Pliny the Elder, *Natural History* 12.48, 13.2, 14.15, trans. J. Bostock & H. T. Riley (1855), Perseus Digital Library.
- Folkard, R. (1884). *Plant Lore, Legends, and Lyrics*, “Acorus.” Project Gutenberg #44638.
- European Medicines Agency (2005). *Public statement on the use of herbal medicinal products containing asarone*.
- Taylor, J. M., et al. (1967). “Toxicity of oil of calamus.” *Toxicology and Applied Pharmacology* 10.

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*Sweet flag.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-10-01. The Thinking Press. https://thethinkingpress.org/materia-medica/sweet-flag

Historical description, not medical advice.