MEDICINAL AND AROMATIC CROPS (2+1)

Harvesting and yield

During the first year, the crop is ready for harvest 8 months after planting and only 2 harvests are obtained. In subsequent years, 3 to 4 harvests at 100 to 120 days intervals can be taken. Depending upon the exposure of the plantation, the plants start flowering earlier in warmer and low altitude areas and later on the high slopes.

Harvesting should begin at the time of 50% blossoming and continue till 75-90% inflorescence emerges and must end when the flowers have finished blossoming. The shoots are cut for distillation when they have reached their maximum size, but have not become woody. The hardwood should not be distilled as it imparts an odour of turpentine.

Essential oil is obtained by steam-distillation of the freshly harvested herbage. The herbage can also be shade-dried, stored and distilled at convenience without any loss of oil.

The time required to distil one charge is 3 hours. Recently, the CIMAP, Bangalore, has recommended that rosemary be distilled for 2 hours for the maximum recovery of oil.

In the laboratory, the fresh rosemary leaves yield 1% and shade-dried leaves yield 3% oil. However, in field-distillation units a yield of 0.7% is considered satisfactory. About 12 to 15 t/ha/year of herbage, yielding about 85 to 100 kg of oil is obtained.