Provided is a method of producing one or more sesquiterpene compounds comprising: contacting an acyclic FPP precursor with a polypeptide having terpene synthase activity, wherein the polypeptide comprises an amino acid sequence that has at least 55% sequence identity to SEQ ID NO: 1, to produce one or more terpenes selected from the group consisting of isovalencene, spirovetiva-1(10),7(11)-diene and valencene or derivatives thereof, or mixture of sesquiterpenes comprising one or more of isovalencene, spirovetiva-1(10),7(11)-diene and/or valencene; and optionally isolating the one or more terpenes or the mixture. Also described is a nucleic acid derived from Vetiveria zizanoides encoding a polypeptide having sesquiterpene synthase activity, a polypeptide that can be used to produce one or more sesquiterpenes or a mixture of sesquiterpenes comprising one or more of isovalencene, spirovetiva-1(10),7(11)-diene and/or valencene, and a non-human organism or cell comprising the nucleic acid or comprising an expression vector comprising the nucleic acid.