The essential oils of four Teucrium species were studied and 131 components, in all, were identified. All oils were rich in sesquiterpenes (50.0-61.9%). Caryophyllene and caryophyllene oxide were the main components of Teucrium arduini; germacrene D, delta-cadinene and gamma-cadinene predominated in Teucrium maghrebinum. Carvacrol and caryophyllene predominated in Teucrium polium ssp. capitatum, while carvacrol, caryophyllene oxide and caryophyllene were the most abundant components in Teucrium montbretii ssp. heliotropiifolium. The germination of radish and garden cress was less sensitive to the four essential oils. The radicle elongation, above all, of radish was significantly inhibited by all oils, in particular by the essential oil of T. arduini, at the highest doses tested. Among the main components of the oils, monoterpenes resulted the more active compounds.