Seasonal fluctuation of essential oil content in lemon verbena (Aloysia triphylla)

Lemon verbena is an aromatic shrub native to Chile, Argentina, and Peru. Its leaves have a pleasant odour, similar to that of lemon, due to the content of essential oils. The effects of the time of year and the time of day of harvesting on essential oil concentrations, yield, percentage of the principle component citral, and leaf area were studied in a two-year-old plantation with 6,667 plants /ha in Talca, central region of Chile (35 degrees S). Samples were taken every two weeks from October (springtime) to April (autumn). To study the fluctuations of essential oil concentration during the day, samples were taken every three hours from 7.30 a.m. to 7.30 p.m. on five different days between December and April. Maximum essential oil concentration was found in young leaves in October with 0.95 ml/100 g DW, decreasing to values of 0.09 to 0.20 ml/100 g DW from December to April. Essential oil yield increased from October to March, reaching a maximum of 27.3 l/ha. Citral content was highest in November (up to 64%), than decreased to reach a minimum in December (34%). From February Values maintained stable (52-45%). In November largest leaf areas were found with 9.2 cm(2)/leaf. No differences in essential oil concentration between different times of day of harvesting could be found. Citral content increased during the day.