Achillea collina is cultivated in the European Alps for its chamazulenecontaining essential oil. In Switzerland, ‘Spak’ is a homogenous and productive cultivar that was developed by Agroscope to match the local climatic conditions. Up to now, Swiss producers used to harvest at the BBCH stage 65 (>50% of plants blooming) and at 15-20 cm from the ground in order to exclude the colourless basal leaves and the ligneous stems. However, as a result of harvest procedure, the amount of non-ligneous stems in the dry matter tends to become too high, and plants with longer stems were shown to have lower essential oil and chamazulene contents. In 2009 and 2010, the influence of phenological stages on yield and quality was studied. The maximum dry weight was achieved at full-bloom stage. However, the leave/stem ratio of 35% in 2010 was too low due to a cutting height at 20 cm above ground. The highest essential oil content in the leaves and flowers was obtained at the ‘early-bloom’ stage. In contrast, the chamazulene content in the essential oil was not influenced by the harvest stages. In conclusion, harvesting the upper 60 cm horizon of the plants at ‘earlybloom’ to ‘full-bloom’ stages (20-50% of blooming plants) is recommended for A. collina. This resents the best compromise between dry matter yield and quality.
