Yield - tonnes per hectare per year
Conservative
Fresh:12 tonnes
Dry: 2 tonne
Oil: 10 to 20 litres
Average
Fresh: 22 tonnes
Dry: 6 tonnes
Oil: 25 to 50 litres
Good
Fresh: 30 tonnes+
Dry: 8 tonnes+
Oil: 80 litres+
Harvesting
Harvesting of most commercial rosemary is done mechanically. On smaller production units and in greenhouses it can be done by hand although this does get expensive.
Fresh production: start harvesting the tender new rosemary growth early in the morning when the temperature is still cool. Harvesting of the fresh tips can start as early as 12 weeks after planting seedlings or established cuttings. Dry production: For dried rosemary production, cutting can be started as soon as there are enough leaves to be harvested. Most of the vegetative growth is trimmed before flowering commences.
The cuttings are then dried at 38°C using a forced air drier. Essential oil production: The best essential oils come from distilling just the flowering tips of the rosemary plant and this is sold as speciality oil and attains a higher value.
Thereafter when the flowering has stopped it is a practice to cut the rest of the foliage for distilling leaving the plant enough growth to regenerate before winter and the following spring flower. This oil is marketed separately.
Storage
Fresh production: After harvesting store fresh rosemary at 5°C. The rosemary can be stored for about 2 weeks. The relative humidity in storage should be kept above 90% to prevent the leaves from losing moisture. Fresh herbs lose their culinary flavour fast so it is best to market and use fresh cut rosemary as quickly as possible.
Dry production: The dried leaves are packaged in airtight containers as soon as possible so they retain their colour and flavour. Keep at about 10°C. Essential oil: Store bottled essential oils in a dry dark and cool space for about a year to 18 months after bottling. After this the oils start to lose their potency and odour.
Pests
Mealybug, Scale, Spider mite, Thrips and White fly are common pests.Diseases
Powdery mildew, Root rots. Rosemary has few pests and diseases but it is best to follow a crop protection regime prescribed by an extension officer or agronomist.
The local chemical salesmen generally have the right programs or could provide information as to the best advisors available in close proximity to the production area.
By Louise Brodie