The berries are used for the production of the volatile oil which is a prime ingredient in Geneva or Hollands Gin, upon which its flavour and diuretic properties depend. Although these valuable berries are produced from a native shrub, the berries of commerce are chiefly collected from plants cultivated in Hungary. The oil distilled on the Continent, principally in Hungary, is chiefly from freshly-picked berries. It has, hitherto, not been possible to produce the oil competitively with Southern Europe because of the relative cheapness of labour and the vast tracts of land over which the trees grow wild. But the rise in the price of foreign oil of Juniper berries since the outbreak of war has directed attention to the possible extended production of the oil either in Great Britain or her northern colonies.
Sunny slopes are likely to be the best places to cultivate the shrub for the berries.
The yield of oil, however, varies considerably in different years. There is a wide difference in the chemical and physical characters of the oil distilled on the Continent from fresh and that in England from imported berries, which in transit to this country have become partially dried. Juniper berries take two or three years to ripen, so that blue and green berries occur on the same plant. Only the blue, ripe berries are here picked. When collected in baskets or sacks, they are laid out on shelves to dry a little, during which process they lose some of the blue bloom and develop the blackish colour seen in commerce.