The difference in yield and composition of essential oil of Thymus ser
pylloides subsp. serpylloides ('thyme of the Sierra') has been investi
gated. The research included all of its different phenological stages,
its sexual characteristics, during three consecutive years. Quantitat
ive analysis of the essential oil revealed that there is a predominanc
e of both aromatic alcohols (carvacrol being the most abundant compone
nt in this group) and their precursors (gamma-terpinene and p-cymene).