Nature Bulletin No. 73 July 6, 1946
Forest Preserve District of Cook County
Clayton F. Smith, President
Roberts Mann, Superintendent of Conservation
The oak is celebrated in history and fable. Great forests of oak once
covered much of England and central Europe. The ancient Druids held
the oak especially sacred and performed their mysterious rites in the
depths of the oak forests. Our modern oaks, of which there are more
than 275 species distributed over the world -- largely in temperate
regions -- are descendants of prehistoric trees. Some 20 or 30 forms
have been identified from fossils as existing during the Ice Age.
The oaks dominate our upland woods in the Middle West. Of 54
species in the United States, Illinois has 19. Cook County has 9, of
which only 6 are common: the white, the swamp white, the bur, the
black, the red and Hill's black ( or northern pin oak). Less common are
the true pin oak, the shingle oak and the chinquapin.
All oaks bear acorns, a fruit peculiar to them. Oaks are divided into two
groups. The "white oak" group, including the white, swamp white, bur
and chinquapin, bear acorns that mature that same fall and the mature
leaves have rounded tips. The inside of the cup over the acorn is
smooth; the bark of the mature tree is scaly. The "black oak" group,
including the black, red, Hill's black, pin and shingle oaks, bear acorns
maturing the next spring and their mature leaves have sharp tips. The
inside of the acorn cup is silky-hairy; the bark is dark, tight, and
furrowed on the older trunks but not scaly.
Acorns are valuable food for hogs and all-important as winter food for
squirrels. Those of the white oak group are sweet and edible, especially
the chinquapin. During the Civil war, acorns served many a family as a
substitute for flour and, when roasted with chicory, for coffee.
The name "oak" has come to stand for great strength and durability.
Very slow-growing, they are the longest-lived and most valuable of our
hardwood trees. They have many uses for furniture, structural timbers,
agricultural implements, railroad ties, fence posts and barrels.
Count the annual growth rings on the next big oak stump you see. Don't
be surprised if you find it to be 300 years old.
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Update: June 2012