Acorus calamus

Tracheophyta MagnoliopsidaAraceaeAcorusAcorus calamus


A rhizomatous perennial herb growing at the margins of streams, canals, ponds and lakes in shallow, nutrient-rich calcareous water. The European plant is a sterile triploid. Lowland.



World Distribution

Native plants are diploid (Siberia, N. America) or tetraploid (S. & E. Asia); the origin of the triploid is unknown but it is naturalised in Europe & W. Asia, the Himalayas and eastern N. America.

© P. Shannon

Broad Habitats

Light (Ellenberg): 8

Moisture (Ellenberg): 10

Reaction (Ellenberg): 7

Nitrogen (Ellenberg): 7


Salt Tolerance (Ellenberg): 0

January Mean Temperature (Celsius): 3.6

July Mean Temperature (Celsius): 15.8

Annual Precipitation (mm): 770

Life form information

Height (cm): 112

Perennation - primary


Life Form - primary

Perennial hydrophyte (perennial water plant)



Clonality - primary

Rhizome far-creeping

Distribution information

Count of 10km squares in Great Britain: 515

Count of 10km squares in Ireland: 17

Count of 10km squares in the Channel Isles: 4

Atlas Change Index: 0.69

Weighted Changed Factor: -2

Weighted Change Factor Confidence (90%)


Distribution information

JNCC Designations


PLANTATT - Attributes of British and Irish plants. (.zip 1455KB) This dataset was compiled and published in 2004, and last updated in November 2008. Download includes an Excel spreadsheet of the attributes, and a PDF explaining the background and nomenclature. Note that the PDF version is the booklet as published, whereas the Excel spreadsheet incorporates subsequent corrections. A hardcopy can be purchased from the Centre for Ecology and Hydrology.

Atlas text references

Atlas (343a)
Hultén E, Fries M
1986.  Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
Preston CD, Croft JM
1997.  Aquatic plants in Britain and Ireland.