Abstract The essential oils of fresh flowers and a combination of leaves plus stems of flowering and nonâflowering Ageratum conyzoides L. growing in two different climatic conditions were analysed by gasâliquid chromatography and mass spectrometry. The composition of the oils of the flowers and the combination of the leaves plus stems were similar except for quantitative variations. The oils are rich in sesquiterpenes and ageratochromene (6,7âdimethoxyâ2,2âdimethylchromene) and 7âmethoxyâ2,2âdimethylchromene.