Plant Profile

Sweet Flag

Compiled by the Omnia Sana editorial team from the plant database ·Last updated August 14, 2026

Acorus calamus

Family: Acoraceae · Parts used: Rhizome · Also known as: Calamus, Sweet sedge, Sweet root

The complete database record: 2 documented constituents, 7 pharmacological actions, 10 traditional / indicated uses, with 24 cited sources.

Botanical Description

Aromatic, semi-aquatic perennial herb spreading by a thick, branching, aromatic rhizome that creeps horizontally in mud at the water's edge. The leaves are erect, sword-shaped (ensiform), bright green and arranged in a fan like an iris, with a distinctive off-centre midrib and one crinkled, wavy margin. A small, finger-like, greenish-yellow flower spike (spadix) emerges obliquely part-way up a leaf-like flowering stem in summer, but in cool temperate climates the plant rarely sets viable seed and spreads mainly by rhizome division.^[14]

Height: 50-150 cm (leaves)

Habit: Erect, rhizomatous, semi-aquatic perennial herb

Leaves: Erect, sword-shaped, iris-like, with an off-centre midrib and one wavy margin; strongly aromatic when crushed

Flowers: Small greenish-yellow flowers crowded on a finger-like spadix borne obliquely on a leaf-like stalk

Stem: Leaf-like flowering stalk arising from the rhizome; the true stem is the underground rhizome

Root: Thick, branching, aromatic creeping rhizome

Fruit: Rarely sets viable seed in temperate climates; propagates mainly by rhizome division

Flowering Period: Late spring to summer

Habitat & Distribution

Grows in shallow water and wet mud at the margins of ponds, lakes, slow-moving rivers and marshes. Native to Asia and North America and long naturalised across Europe, where it was historically cultivated and traded for its aromatic rhizome.^[14]

Harvesting

The rhizome is dug from autumn to early spring, when its aromatic oil content is highest, then washed, peeled and dried; the strong sweet-spicy fragrance released on cutting helps confirm correct identification against non-aromatic look-alikes such as yellow flag iris.^[14]

Parts: Rhizome

Season: Autumn to early spring

Key Constituents

Phenylpropanoid asarones (alpha- and beta-asarone)^{[10, 13, 14]}

Characteristic aromatic constituents - but beta-asarone is the toxic, safety-limiting compound.

Asarones (alpha-/beta-asarone)

Essential oil and lignans^{[7, 14]}

Other aromatic and bioactive constituents of the rhizome.

Essential (volatile) oilLignans

Pharmacological Actions

Anticancer (preclinical)^{[12, 17, 18, 19, 20, 21]}

Rhizome extracts and the constituent beta-asarone show antiproliferative, pro-apoptotic, anti-invasive and chemosensitizing/chemopreventive activity across gastric, bladder and esophageal cancer models (preclinical).

Anticonvulsant^{[10, 14, 22]}

Traditional nervine for memory and concentration (preclinical neuroprotective, anticonvulsant and antidepressant-like activity)

Antidepressant / mood support^{[9, 14, 22]}

Traditional nervine for memory and concentration (preclinical neuroprotective, anticonvulsant and antidepressant-like activity)

Anxiolytic / calming^{[9, 14, 22]}

Traditional nervine for memory and concentration (preclinical neuroprotective, anticonvulsant and antidepressant-like activity)

Bitter digestive tonic / stomachic^[14]

Aromatic bitter / carminative for indigestion, bloating, flatulence and poor appetite (traditional)

Carminative^{[6, 14]}

Aromatic bitter / carminative for indigestion, bloating, flatulence and poor appetite (traditional)

Neuroprotective / cognition support^{[1, 3, 5, 14, 22]}

Traditional nervine for memory and concentration (preclinical neuroprotective, anticonvulsant and antidepressant-like activity)

Traditional & Indicated Uses

Anxiety^{[14, 22]}Good · 7/10

inferred from anxiolytic action

Evidence: 7

Label: Anxiety

more plants for anxiety →detailed sources →

Loss of appetite^[14]Good · 7/10

Aromatic bitter / carminative for indigestion, bloating, flatulence and poor appetite (traditional)

Evidence: 7

Label: Loss of appetite

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Bloating^[14]Good · 7/10

Aromatic bitter / carminative for indigestion, bloating, flatulence and poor appetite (traditional)

Mechanistic Exclude Ids: REF-2274

Evidence: 7

Label: Bloating

more plants for bloating →detailed sources →

Cancer (anticancer research)^{[12, 17, 18, 19, 20, 21]}Good · 7/10

Acorus calamus extract inhibits gastric cancer (AGS) growth and angiogenesis; its constituent beta-asarone induces apoptosis and suppresses invasion/EMT in gastric, esophageal and bladder cancer cells and sensitizes them to chemotherapy (preclinical).

Evidence: 7

Label: Cancer (anticancer research)

more plants for cancer (anticancer research) →detailed sources →

Cognitive function^{[14, 22]}Good · 7/10

Traditional nervine for memory and concentration (preclinical neuroprotective, anticonvulsant and antidepressant-like activity)

Evidence: 7

Label: Cognitive function

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Low mood / depression^{[14, 22]}Good · 7/10

inferred from antidepressant action

Evidence: 7

Label: Low mood / depression

more plants for low mood / depression →detailed sources →

Indigestion^[14]Good · 7/10

Aromatic bitter / carminative for indigestion, bloating, flatulence and poor appetite (traditional)

Evidence: 7

Label: Indigestion

more plants for indigestion →detailed sources →

Memory^{[14, 22]}Good · 7/10

Traditional nervine for memory and concentration (preclinical neuroprotective, anticonvulsant and antidepressant-like activity)

Evidence: 7

Label: Memory

more plants for memory →detailed sources →

Nervous tension^{[14, 22]}Good · 7/10

inferred from anxiolytic action

Evidence: 7

Label: Nervous tension

more plants for nervous tension →detailed sources →

Stress^{[14, 22]}Good · 7/10

inferred from anxiolytic action

Evidence: 7

Label: Stress

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Traditional Use & History

Sweet flag rhizome is a classic aromatic bitter and nervine of Ayurvedic and East Asian traditional medicine, used for indigestion, bloating, flatulence and poor appetite, and as a nervine tonic for memory, concentration and mild nervous complaints.^[14]

Preparations

Decoction^[14]

Dried, peeled rhizome simmered in water as a bitter digestive and nervine decoction.

Dosage

All preparations^{[13, 14]}

Because beta-asarone is hepatotoxic, mutagenic and carcinogenic in animal studies and its content varies widely between varieties, no general dose is given here; internal use should be restricted to properly characterised, beta-asarone-free preparations under professional guidance. Educational reference only, not a prescription.

Safety, Cautions & Contraindications

Safety note^{[13, 14]}Serious

SERIOUS: beta-asarone is hepatotoxic, mutagenic and carcinogenic in animal studies. Regulators have restricted internal use of asarone-containing Acorus calamus (the Asian high-beta-asarone varieties), and it is banned as a food additive in the USA. Avoid internal use except properly characterised beta-asarone-free preparations.

Safety note^[13]Caution

Do not use in pregnancy or breastfeeding, or for prolonged periods. The North American variety (Acorus americanus) is essentially beta-asarone-free, but most commercial calamus is not.

Dangerous Lookalikes

Iris Pseudacorus^{[23, 24]}Irritant

Confused Part: Sword-shaped leaves and the aromatic rhizome gathered from wet ground; yellow flag iris grows in the same wet habitat with near-identical sword-shaped leaves.

Confusion Context: Sweet flag (Acorus calamus) is foraged in marshes and pond margins for its aromatic rhizome and leaves. Yellow flag iris (Iris pseudacorus) grows in exactly the same wet habitat and has near-identical erect sword-shaped leaves - its very name pseudacorus means 'false sweet-flag.' Iris pseudacorus is a low-severity poison: all parts, especially the rhizome, cause salivation, vomiting and diarrhoea if eaten, and the sap can irritate skin. Because a non-flowering iris clump is easily taken for sweet flag, and the prized part (the rhizome) is the most toxic part of the iris, this is a genuine foraging hazard.

Distinguishing Features: SMELL (decisive): crush a leaf or the rhizome. Sweet flag is strongly and sweetly aromatic (spicy/citrus). Yellow flag iris has no such fragrance - it is odourless., Leaf detail: sweet flag has a prominent off-centre raised midrib and one crinkled/wavy leaf margin. Iris leaves are flat and plain with a central midrib and straight (not wavy) margins., Flower/structure: sweet flag bears a unique finger-like green spadix angling out from the side of a leaf-like stalk. Yellow flag iris bears showy bright-yellow iris flowers. If it has a yellow iris flower, it is not sweet flag.

Key Test: Crush a leaf and smell it. A strong sweet, spicy-citrus aroma with a wavy leaf margin and an off-centre midrib = sweet flag. No fragrance, flat leaves with straight margins, and (in season) bright-yellow iris flowers = yellow flag iris - do not eat; its rhizome causes vomiting and diarrhoea. If there is no aroma, do not use it.

Reviewed By: Omnia Sana (owner-authorized)

Reviewed Date: 2026-07-07

Harvest Readiness

^{[15, 16]}

Part: rhizome

Signals: Dig the rhizome in the dormant season - from late autumn once the top has died back, through to early spring before the new leaves emerge - lifting it while still firm, before it turns hollow., Confirm identity before digging: the wet-ground rhizome and sword-like leaves are confusable with the toxic, NON-aromatic yellow flag iris (Iris pseudacorus); true Acorus calamus is strongly sweet-aromatic when cut. See this plant's Dangerous Lookalikes.

Basis: traditional

Source Quote: The rhizome should be gathered in early spring or in October and November, freed from dirt and its bitter rootlets, and dried quickly in a gently warmed room.

Independent Confirmation: Grieve (REF-3186) independently gives the same dormant-season window - 'Late autumn or early spring is the time chosen for collection' - and adds the readiness cue that the rhizomes are lifted 'before they lose their firmness and become hollow'.

Species Confirmed: 1

External Identifiers

GBIF ›Plants of the World Online ›Wikidata ›

References & Sources

Sharma, V., Singh, I. and Chaudhary, P (2014) 'Acorus calamus (The Healing Plant): a review on its medicinal potential, micropropagation and conservation', Natural Product Research, 28(18), pp. 1454-1466. doi:10.1080/14786419.2014.915827 Traditional / reference
https://doi.org/10.1080/14786419.2014.915827
Khwairakpam, A.D., Damayenti, Y.D., Deka, A., Monisha, J., Roy, N.K. et al (2018) 'Acorus calamus: a bio-reserve of medicinal values', Journal of Basic and Clinical Physiology and Pharmacology, 29(2), pp. 107-122. doi:10.1515/jbcpp-2016-0132 Traditional / reference
https://doi.org/10.1515/jbcpp-2016-0132
Ukkirapandian, K., Kayalvizhi, E., Udaykumar, K.P., Kandhi, S. and Muthulakshmi, R (2022) 'The Neuroprotective Role of Acorus calamus in Developmental and Histopathological Changes in Autism-Induced Wistar Rats', Cureus, 14(9), pp. e29717. doi:10.7759/cureus.29717 Preclinical
https://doi.org/10.7759/cureus.29717
Haran, P., Shanmugam, R. and Deenadayalan, P (2024) 'Free radical scavenging, anti-inflammatory and antibacterial activity of Acorus calamus leaves extract against Pseudomonas aeruginosa and Staphylococcus aureus', Cureus, 16(3), pp. e55987. doi:10.7759/cureus.55987 Preclinical
https://doi.org/10.7759/cureus.55987
Kalra, S., Sachdeva, H., Bhushan Pant, A. and Singh, G (2024) 'Acorus calamus Linn.: a novel neuroprotective approach for traumatic brain injury in Drosophila melanogaster', Brain Research, 1836, pp. 148953. doi:10.1016/j.brainres.2024.148953 Preclinical
https://doi.org/10.1016/j.brainres.2024.148953
Joshi, R.K (2016) 'Acorus calamus Linn.: phytoconstituents and bactericidal property', World Journal of Microbiology & Biotechnology, 32(10), pp. 164. doi:10.1007/s11274-016-2124-2 Preclinical
https://doi.org/10.1007/s11274-016-2124-2
Hao, Z., Zhang, Y., Cao, Y., Sun, Y., Wang, Y., Zhang, C., Liang, D., Liu, Y. and Feng, W (2023) 'Chemical constituents from Acorus calamus with potent anti-diabetic and hepatoprotective activities', Fitoterapia, 169, pp. 105591. doi:10.1016/j.fitote.2023.105591 Preclinical
https://doi.org/10.1016/j.fitote.2023.105591
Olas, B. and Brys, M (2017) 'Is it safe to use Acorus calamus as a source of promising bioactive compounds in prevention and treatment of cardiovascular diseases?', Chemico-Biological Interactions, 281, pp. 32-36. doi:10.1016/j.cbi.2017.12.026 Meta-analysis / review
https://doi.org/10.1016/j.cbi.2017.12.026
Rajput, S.B., Tonge, M.B. and Karuppayil, S.M (2013) 'An overview on traditional uses and pharmacological profile of Acorus calamus Linn. (Sweet flag) and other Acorus species', Phytomedicine, 21(3), pp. 268-276. doi:10.1016/j.phymed.2013.09.020 Meta-analysis / review
https://doi.org/10.1016/j.phymed.2013.09.020
Bai, Y., Sun, Y., Xie, J., Li, B., Bai, Y., Zhang, D., Liang, J., Xiao, C., Zhong, A., Cao, Y. and Zheng, X (2019) 'The asarone-derived phenylpropanoids from the rhizome of Acorus calamus var. angustatus Besser', Phytochemistry, 170, pp. 112212. doi:10.1016/j.phytochem.2019.112212 Preclinical
https://doi.org/10.1016/j.phytochem.2019.112212
Huang, L., Feng, Z., Xiang, J., Deng, M. and Zhou, Z (2024) 'Anti-inflammatory compounds from the rhizome of Acorus calamus and their mechanism', Natural Product Research, 38(20), pp. 3669-3675. doi:10.1080/14786419.2023.2255919 Preclinical
https://doi.org/10.1080/14786419.2023.2255919
Das, B.K., Swamy, A.V., Koti, B.C. and Gadad, P.C (2019) 'Experimental evidence for use of Acorus calamus (asarone) for cancer chemoprevention', Heliyon, 5(5), pp. e01585. doi:10.1016/j.heliyon.2019.e01585 Meta-analysis / review
https://doi.org/10.1016/j.heliyon.2019.e01585
Uebel, T., Hermes, L., Haupenthal, S., Muller, L. and Esselen, M (2020) 'alpha-Asarone, beta-asarone, and gamma-asarone: Current status of toxicological evaluation', Journal of Applied Toxicology. doi:10.1002/jat.4112 Traditional / reference
https://doi.org/10.1002/jat.4112
He, X., Chen, X., Yang, Y., Liu, Y. and Xie, Y (2023) 'Acorus calamus var. angustatus Besser: Insight into current research on ethnopharmacological use, phytochemistry, pharmacology, toxicology, and pharmacokinetics', Phytochemistry. doi:10.1016/j.phytochem.2023.113626 Meta-analysis / review
https://doi.org/10.1016/j.phytochem.2023.113626
Felter, H. W. and Lloyd, J. U (1898) 'Calamus (Acorus calamus) — King's American Dispensatory'. Available at: https://www.henriettes-herb.com/eclectic/kings/acorus.html Traditional / reference
https://www.henriettes-herb.com/eclectic/kings/acorus.html
Grieve, M (1931) 'Sedge, Sweet (Acorus calamus) — A Modern Herbal'. Available at: https://botanical.com/botanical/mgmh/s/sedges39.html Traditional / reference
https://botanical.com/botanical/mgmh/s/sedges39.html
Liu, B. and Dan, W. and Wei, Y. and Zhang, Y. and Wang, C. and Lei, Y. and Hou, T. and Zhang, Y. and Gao, Y (2023) 'beta-asarone inhibits the migration, invasion, and EMT of bladder cancer through activating ER stress', Cancer Medicine, 12(12), pp. 13610-13622. doi:10.1002/cam4.6059 Preclinical
https://doi.org/10.1002/cam4.6059
Hu, Y. and Li, Z. and Gong, L. and Song, Z (2022) 'beta-Asarone suppresses TGF-beta/Smad signaling to reduce the invasive properties in esophageal squamous cancer cells', Medical Oncology, 39(12), pp. 243. doi:10.1007/s12032-022-01847-0 Preclinical
https://doi.org/10.1007/s12032-022-01847-0
Tao, H. and Ding, X. and Wu, J. and Liu, S. and Sun, W. and Nie, M. and Pan, X. and Zou, X (2020) 'beta-Asarone Increases Chemosensitivity by Inhibiting Tumor Glycolysis in Gastric Cancer', Evidence-Based Complementary and Alternative Medicine, 2020, pp. 6981520. doi:10.1155/2020/6981520 Preclinical
https://doi.org/10.1155/2020/6981520
Rahamooz Haghighi, S. and Asadi, M.H. and Akrami, H. and Baghizadeh, A (2017) 'Anti-carcinogenic and anti-angiogenic properties of the extracts of Acorus calamus on gastric cancer cells', Avicenna Journal of Phytomedicine, 7(2), pp. 145-156. Preclinical
https://scholar.google.com/scholar?q=Anti-carcinogenic%20and%20anti-angiogenic%20properties%20of%20the%20extracts%20of%20Acorus%20calamus%20on%20gastric%20cancer%20cells
Wu, J. and Zhang, X.-X. and Sun, Q.-M. and Chen, M. and Liu, S.-L. and Zhang, X. and Zhou, J.-Y. and Zou, X (2015) 'beta-Asarone inhibits gastric cancer cell proliferation', Oncology Reports, 34(6), pp. 3043-3050. doi:10.3892/or.2015.4316 Preclinical
https://doi.org/10.3892/or.2015.4316
Sharma, V., Sharma, R., Gautam, D.S., Kuca, K., Nepovimova, E. and Martins, N (2020) 'Role of Vacha (Acorus calamus Linn.) in Neurological and Metabolic Disorders: Evidence from Ethnopharmacology, Phytochemistry, Pharmacology and Clinical Study', Journal of Clinical Medicine, 9(4). doi:10.3390/jcm9041176 Traditional / reference
https://doi.org/10.3390/jcm9041176
North Carolina Extension Gardener Plant Toolbox (2024) 'Acorus calamus (Sweet Flag)'. Available at: https://plants.ces.ncsu.edu/plants/acorus-calamus/ Traditional / reference
https://plants.ces.ncsu.edu/plants/acorus-calamus/
North Carolina Extension Gardener Plant Toolbox (2024) 'Iris pseudacorus (Yellow Flag)'. Available at: https://plants.ces.ncsu.edu/plants/iris-pseudacorus/ Traditional / reference
https://plants.ces.ncsu.edu/plants/iris-pseudacorus/

Selected studies & references

ReviewAcorus calamus var. angustatus Besser: Insight into current research on ethnopharmacological use, phytochemistry, pharmacology, toxicology, and pharmacokinetics source↗ (2023)

ReviewExperimental evidence for use of Acorus calamus (asarone) for cancer chemoprevention source↗ (2019)

ReviewIs it safe to use Acorus calamus as a source of promising bioactive compounds in prevention and treatment of cardiovascular diseases? source↗ (2017)

ReviewAn overview on traditional uses and pharmacological profile of Acorus calamus Linn. (Sweet flag) and other Acorus species source↗ (2013)

PreclinicalAcorus calamus Linn.: a novel neuroprotective approach for traumatic brain injury in Drosophila melanogaster source↗ (2024)

PreclinicalAnti-inflammatory compounds from the rhizome of Acorus calamus and their mechanism source↗ (2024)

PreclinicalFree radical scavenging, anti-inflammatory and antibacterial activity of Acorus calamus leaves extract against Pseudomonas aeruginosa and Staphylococcus aureus source↗ (2024)

Preclinicalbeta-asarone inhibits the migration, invasion, and EMT of bladder cancer through activating ER stress source↗ (2023)

All 20 studies in the Knowledge Finder →

Educational use only. This profile summarises traditional and scientific sources for reference. It is not medical advice and not a substitute for a qualified practitioner. Some plants carry safety cautions and drug interactions - always check before use.
This profile is assembled automatically from the Omnia Sana plant database, which we curate by hand. How this site is built.

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