Monoterpenes in sitka spruce: Within tree and seasonal variation

The composition of oils from needles and cortex of Sitka spruce is unique. Cortex oil is essentially all monoterpene hydrocarbons, while needle oil may be up to 50% oxygenated monoterpenes. Very wide seasonal variations in composition occur in needle oil in young tissue. At bud burst, the oil is > 95% myrcene; this drops to about 40% at the end of summer. The oxygenated terpenes camphor and piperitone develop to about 20% each in concentration during the growing season.