The generic name Olea is from the Greek elaia, derived from the Celtic or Gothic olew, oil, on account of the abundance of oil in the fruit. The specific name europaea is given to the species cultivated throughout Europe.
The olive has been given fanciful names by the early peoples. It was known as the “tree of wisdom,” “Minerva’s tree,” the “Gift of Heaven,” etc. The Greeks consecrated the tree to Minerva, and made it the symbol of wisdom, abundance, and peace.
Description
The olive is an evergreen tree about 20 to 30 feet high, much branched and spreading. It forms a symmetrical head, having angular branches and opposite leaves. The leaves are dry and leathery in texture, lanceolate, entire, deep green above, and light hoary beneath. The flowers are small, star-shaped, creamy white with yellow centers, have a faint pleasing odor, and are axillary in compact racemes. The fruit, a fleshy pendulous drupe, is very abundant. It is oval, obovate, or globular in shape, about the size of a pigeon’s egg, dull greenish yellow even when full size but unripe, then gradually becomes yellow, red, and finally turns a glossy purplish black or black when ripe. In ripening, the side exposed to the sun reddens, then gradually the whole fruit changes from red to purple, then black. As fruit of all degrees of ripeness are developed at the same time, the tree furnishes an extremely beautiful combination of colors, the various greens of the leaf and fruits forming a background for the splotches of red, purple, and black formed by the ripening fruit. The fruit is peculiar in two respects, first, in that it contains in addition to the ordinary constituents of fruits an abundance of edible oil, consequently making it a valuable food; second in that it contains a bitter substance which does not disappear on maturity, so that the fruit cannot be eaten at any stage in its development without preliminary treatment for the elimination of this substance. The stone is two-celled, many times only one seed developing.
Climatic Requirements
The olive requires rather warm temperature, light humidity, and absence of heavy frosts. It can withstand temperatures of -7 to -8 degrees C. or even lower if not too prolonged, and if the change to higher temperature be gradual. Moist cold is more unfavorable than dry. The altitude at which it will grow depends on the local climate. The climate of the countries bordering on the Mediterranean and that of California are particularly favorable.
Varieties
The wild olive Oleaster is said to have been the original form, called by Linnaeus Olea europaea sylvestris, later by De Candolle Olea europaea oleaster and the cultivated form Olea europaea sativa. The reason for this belief is said to be the oleaster seeds reproduce trees true to type, whereas the seeds of sativa produce trees having the characteristics of oleaster but, though oleaster under cultivation becomes modified in various ways, it does not produce fruit like sativa. Whichever form was the original, the subjection to cultivation for over 4,000 years, under the varying conditions of soil, climate, and methods of cultivation, has produced many varieties. Many of these doubtless are the result of accidental modifications, more or less fixed by successive cultivations. At the present time there are certain well-defined varieties which are cultivated, and of which the characteristics are well known, so that varieties may be selected according to the purpose desired, whether for the preservation of the fruit green, half ripe, or ripe, or for extraction of oil.
Of the large number of varieties introduced into California, Wickson reports analyses made by the State university on 57 varieties. Of these only a comparatively few were retained as worthy of cultivation, chief among these being the Mission olive, the one planted originally in California in the old mission gardens. Wickson states there are several sub-varieties of this form.