Naturally the olive is a dry-climate fruit; that is, it needs a dry air as well as a relatively dry soil. Dr. Henry Lansdell says in his "Russian Central Asia:" "In the Zarafshan province there are whole forests of olive-trees." Dr. Albert Regel says in Gartenflora, of Berlin: "In the dry climate of eastern Bokhara, olives are gathered from the wild growth of the foothills and brought to market for dessert and confection. The olive-tree is cultivated largely in Tashkend and in the Kokan country." We have much evidence favoring the truth of the statement that in the dry air of the far East the insects and fungi attacking the olive in the moister climates of the Mediterranean and California are not known.
In California hundreds of thousands of olive-trees have been planted where, from the configuration of the country, too much moist air reached them from the coast. Experience has finally established the fact that it only reaches a profitable perfection of fruit in a dry atmosphere and on a quite rich dry soil, yet it will grow and bear crops in a greater variety of soils and air than almost any subtropical fruit tree. As the years go on it will be demonstrated that the highest quality of olives for oil and pickling will be reached in hot interior valleys of California, and in such warm interior valleys as those of the Salt and Gila rivers in Arizona. The best system of management will be that of early culture during the season of growth, followed by a cover-crop (127. Cover-crops and Blight) and irrigation at the time of sowing the cow-peas or vetch. While the olive will grow on thin land and will endure drought well, the fruit will suffer. It needs some water during the period of fruit development naturally or by irrigation, and it needs the humus and nitrogen following the use of a leguminous cover-crop.
The most experienced growers prefer trees for planting propagated by the slower way of growing seedlings and budding them as we grow hardy deciduous trees. Such trees, as might be expected, are more robust, long lived, and productive than those grown from "tips" under glass, which is the commercial plan. The seeds are slow to germinate. But this amounts to little, as growers who will plant no trees from "tip" cuttings (62. Immature-growth Cuttings) stratify the seeds (5. Seed-stratification) months in advance of planting and keep stratified seeds on hand for use when wanted for planting.
The ancient use of the olive fruit was mainly for oil-producing. The oil in Canaan, Syria, and central Asia was considered an essential to health in the dry, hot Oriental climate and was regarded as a symbol of peace and good-will. In the land of the East it was the substitute for butter and animal fats and an emblem not only of peace but of domestic plenty and prosperity. But the use of pure olive oil in our day has been lessened in all countries, except central Asia, by the immense production of sunflower oil in Russia, which is mainly sold for pure olive oil, and about all the oil of commerce is now either adulterated with cotton-seed oil or sunflower oil, and in many cases the "sweet olive oil" and the "Lucca oil" have not a trace of olive oil in the mixture.
Under such circumstances little olive oil is produced in California or in the United States. The main crop as yet grown in California is used for pickling when green for shipment to the States east of the mountains. Ripe-pickled olives are also prepared in large quantity for use on the west coast. In this form they are a healthy and nutritious food, as well as a luxury. Tourists who will not touch the green-pickled olives use the ripe ones freely. But as yet the ripe ones are rarely obtainable in the Eastern States, as they are not put up in shape for distant shipment, except in expensive bottles for those who can afford to use them. The olive-pickling and oil-producing for market are special processes that require practical instruction not easily given on the printed page.