Wednesday, 23 December 2015


Rosemary herb is versatile and is used  extensively used in British and Italian cuisine. The plant has a delightful fragrance, nutmeg  odour and a rather bitter flavor. Rosemary herb belongs to the family Lamiaceae and there are several species with different chemical composition specific to different origins. Its is used to flavour meats, sauces and vegetable dishes. It is also used for its anti-oxidant properties in industrial manufacture of meat based products. Its oil is widely used in hair shampoos, bath essences, cosmetic, perfumes and insect repellents.

This is a perennial crop and can survive for a long time in one site. Rosemary herb does well at high altitudes and requires neutral to slightly alkaline soil, hence the need for lime if soil pH falls 
below 6.5. The soil should be light and well drained.

 Propagation by farmers who grow Rosemary herb in Kenya is preceded by selection of the right cultivars. To ensure  retention of desired characteristics, Rosemary herb should only be propagated vegetatively. 12.15cm long tip cutting should be taken from young shoots and leaves from the lower half removed, the base of the stem dipped into a rooting powder and the cutting buried 8-10cm in a sandy nursery bed at a spacing of 20x20cm. Under irrigated conditions, cutting can be taken all year round but there is need for co-ordinated planting schedules. Plant should be transplanted to the fields at 4-6 months as bare root plants. Under rain-fed condition, preparing cutting and field planting is best carried out during the rainy season. Planting should be at a spacing of 120x45 cm resulting to a plant population of 20-30 thousand plants per ha.The objective is to produce a dense bush 60cm in diameter with vigorous shoot growth. 
The first harvest is taken when plants are 18-24 months old. Prior to this shoots should be cut back to promote growth and prevent the formation of long, woody stems. When plants are mature, shoots should be cut back by 10-15cm twice yearly to reduce the formation of woody stem. Straggling branches should be pruned hard to promote the production of new shoots. After harvesting, the plants should be ridged up lightly. Weed control should be done regularly as required.

Application rates of fertilizers depends on the fertility of the site. A standard annual application rate of 60kg/ha N, 25kg/ha and 75kg/ha K applied as three equal dressings for N and K and single application for P is required. During planting, the first of the N and K dressing and all of P should be applied during as basal fertilizer and cultivated into the soil. An addition 50 kg/ha N can be applied during the first year to promote vigorous growth and establishment. Top dressings should be banded along the rows.

There are no significant pest and disease problems  experienced by those who grow rosemary herb in Kenya.

A single harvest is done yearly with the first harvest 18-24 months after planting. For production of fresh o dried herb, harvesting is done before flowering, while for essential oil extraction, the crop is cut at flowering. The crop is cut just above the hard wood, which must not be introduced into the still as it taints the oil. Fresh yield range between 8-12 ton/ha producing 2-2.5 tons/ha dried rosemary  herb. Fresh product should be stored at 0.5-1.5c and 95-98% relative humity

The crop should be dried immediately after cutting to avoid loss of the volatile oil and colour. The crop should be dried on racks in the shade. There are no firm recommendation for temperature regimes in artificial dryers, but it is suggested that a maximum temperature of 43 c should be used.

The oil usually obtained from the dry material by distillation, although the fresh material can also be used but is more bulky to handle. Volatile oil content of the crop varies under different environmental condition and with the particular characteristics of the cultivar. Oil content of the fresh material ranges from 0.3-1.5% and an oil yield of 40-60 kg/ha can be expected. The character of the oil is affected by the method of distillation and the length of storage of the plant material prior to distillation. The oil can also be extracted using ethanol or benzine, either directly on fresh material, or on the dried herb after distillation, to give products used as anti-oxidants. 
Grow rosemary herb in Kenya as it is fitting considering climate and soil conditions.