The rhizomesâ essential oils of Acorus calamus L. grown in Estonia were analyzed using SDE micro-method for oil isolation, GC/FID with two columns of different polarities and GC/MS for identification and quantification of oil composition. The oil yield was 2.4â3.3%. Seventy-two constituents were identified from three A. calamus samples comprising over 95% of the oils. β-Asarone (85.3%) was the major constituent in one sample (a characteristic of tetraploid A. calamus). Two samples (probably triploid caryotype) had lower percentage of β-asarone (9.3â10.2), but more acorenone (22.4â27.5%), shyobunone (8.2â13.7%), preisocalamendiol (8.1%) and isoacorone (2.8â5,0%). Strong negative correlations between the contents of β-asarone and other principal compounds of A. calamus oil were found. The β-asarone-rich chemotype of A. calamus was found to be growing in Europe for the first time.