Thuja occidentalis (or Thuja vulgaris) is a coniferous plant in the Cupressaceae family of the genus Thuja.
It is a very leafy and intensely fragrant plant. It originates in the northeastern United States of America and southeastern Canada, and is one of the first American trees to acclimate in Europe. It was introduced to Europe in the 16th century.
The active principles of Tuia consist of an essence of complex composition and somewhat toxic due to the presence of a ketone, the tuiona (or tujona); The plant also contains tannins.