Nature Bulletin No. 524-A April 6, 1974
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation
Many people do not realize that all of our common trees have flowers.
Otherwise they could not produce seeds. We are apt to think of
flowering trees as being those with showy blossoms -- most of them
beautiful and some very fragrant -- such as the redbud, dogwood,
buckeye, horse chestnut, black locust, tulip tree or yellow poplar,
magnolia, and the fruit trees.
However, all of our forest and shade trees have flowers -- of some kind
-- which are just as interesting when examined with a strong reading
glass. Some are grotesque, some exquisitely designed, some extremely
colorful. They offer a new world to be explored and photographed.
Some kinds, such as the elms, bloom profusely but the flowers are so
small and delicately tinted that they are seldom noticed. Others, such as
the poplars, oaks and walnuts, have peculiar flowers in the form of
catkins that, without petals or sepals, do not look like flowers at all. The
sycamore's tiny flowers are packed, in countless numbers, into a tight
round ball that dangles back and forth on a long flexible stem.
Certain species, such as the elms, have "perfect" flowers, each with
stamens that shed pollen and also a pistil that receives it to fertilize an
egg which will develop into a seed. On others, such as the walnuts,
there are male flowers (with stamens) and female flowers (with a pistil)
borne separately on the same tree. On several --notably willows,
cottonwood and other poplars, boxelder, mulberry, Osage orange and
sassafras -- the male and female flowers are borne on separate trees. Of
course, only the females produce seed. There are also species which, on
the same tree, not only have "perfect" flowers but, also, either male or
female flowers or both. All of this may be confusing at first but it will
enhance rather than detract from your enjoyment in the study of tree
Each kind of tree has its own time for blooming. Silver and red maples,
elms, cottonwood, aspen and the redbud bloom in early spring, long
before their leaves appear. Many trees bloom while their leaves unfold
or, like the oaks and hickories, shortly after. A great oak may be so
covered with clusters of tassel-like catkins that its entire crown has a
yellowish or reddish tone. The catalpa, linden and ailanthus bloom last,
in June, long after their leaves are fully developed.
Most trees are wind-pollinated and many of them seem to be in a hurry.
After discharging their pollen, the flowers wither and soon disappear.
Many, however, are pollinated by insects -- particularly those with
showy flowers -- and some, like the black locust and the linden, are so
fragrant and laden with nectar that they attract swarms of honeybees. .
Every year, in May, when the wild crabapples and hawthorns burst into
full bloom, the roadsides and the countrysides around Chicago become
indescribably beautiful and fragrant. Then you should visit our nature
centers where the trails are lined with them. Lombard has a Lilac
Festival and Holland, Michigan, has its Tulip Time. We, in Cook
County, should celebrate Crabapple Week.
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Update: June 2012