Nature Bulletin No. 546-A November 30, 1974
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation
Ages ago, in the crowded countries of the world, men turned to oil-
yielding plants for their fats. As America becomes more thickly
populated and our fertile soils more scarce, we can be sure that our
children and grandchildren will be eating less pork, beef and chicken.
This is because several vegetarians can subsist on the grains and other
plant products necessary to produce the meat that one average
American now eats. Oils from corn, soybeans, peanuts, cottonseed and
coconuts have already replaced most of the animal fats in our diet. But
olive oil, that aristocrat of all edible oils, is also being imported by the
millions of gallons for our fancy cooking and salads. Although a luxury
item to present-day Americans, since ancient times it has been "the fat
of the land" in the countries that border the Mediterranean.
Cultivation of the olive traces back beyond recorded history -- perhaps
farther than any other tree. Its native home, the place where it was first
domesticated, was probably on the limestone hills near the sea between
Greece and Syria. The wild olive is a rather straggling small tree or
bush with thorny branches. The cultivated varieties are more compact
and less spiny with smooth leathery evergreen leaves, grayish-green
above and whitish below. The olive does not begin to bear fruit until
about twenty years of age; but this Methuselah among cultivated trees
continues to yield, sometimes for hundreds of years. Old trees seldom
exceed 30 feet in height, but the gnarled knotty trunk may be over
twenty feet in circumference. The very hard wood with its beautiful
grain and color is prized by cabinetmakers.
The olive is a stone fruit with the appearance of a purple plum when
mature The oil, contained in the flesh, may make up as much as 60
percent of the weight of the fully ripe fruit. The best quality, or rich
yellow "virgin oil" used for salads, is made from hand-picked fruit
which is carefully crushed and squeezed in presses. Speed is essential
because the oil in bruised fruit quickly becomes rancid. Lower grades
of oil are greenish in color and are used for cooking, in medicine, or for
making Castile soap. A total of about one million tons of olive oil is
produced in the world each year. Of this, Spain furnishes over 40
percent, followed by Italy, Greece and Portugal.
Afresh olive picked off the tree, no matter how ripe, has a vile intensely
bitter taste. In making pickled olives, either green or ripe, this flavor is
removed by soaking them in weak lye. Then they are thoroughly
washed, packed in bottles or cans (with or without pimiento stuffing)
When Thomas Jefferson was minister to France during the
Revolutionary War, and continuing for the next 35 years, he imported
olive trees and seeds many times in attempts to establish olive-growing
in our southern states. At about the same time that Jefferson was failing
because of the excessive humidity of the Carolinas and Georgia, the
Spanish padres succeeded in the drier climate of southern California.
There, olive culture did not spread far beyond the Franciscan missions
until about 1890. However, by 1930, forty thousand acres were in olive
orchards, mostly the Mission and Manzanillo varieties. During World
War II, when imports were interrupted, this crop suddenly became very
valuable. Some olives are also grown in Arizona and New Mexico.
Now, the large amount of hand labor required for picking and
processing makes it difficult for American growers to compete with
imported pickles and oil.
Lilac, privet and ash trees are also members of the olive family.
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Update: June 2012