Dendrology Demystified: A Tree Tutorial
by
D.
Glenn Miller
continued from
page one
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Fig. 4 Sugar Maple twigs
with leaves and fruit
Fig. 5
Sugar Maple twigs
Fig. 6
Sugar Maple bark |
Maple
Maples form the other major
group of trees with opposite twigs and leaves. Perhaps the most
familiar of the maples-because of its famous confectioneries is the
sugar maple. Like white ash, sugar maple has opposite leaves and
branching though the leaves of most maples are simple rather than
compound. In contrast to the robust twigs of the white ash, sugar
maple has relatively thin and delicate twigs.
As with other trees, the sugar
maple’s bark is variable but often distinctive. Using a feature like
a tree’s bark for identification, though, once again evokes the
analogy of recognizing a person in a crowd. A photograph or two and a
description, no matter how apt, are no substitute for experience in
the field and simply gaining familiarity.
Horse Chestnuts
The horse chestnuts, or buckeyes, form the only other
major tree group with opposite leaves and branching patterns.
Probably the most familiar species is the Ohio
buckeye. Whereas most maples have simple
Fig. 7
Ohio
Buckeye twig with leaf and fruit.
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leaves, the horse chestnuts have compound leaves.
Recall that the ash also has compound leaves. The horse chestnut
leaves, though, are clearly distinguishable from those of ash because
they’re what’s called palmately compound. In other words, the
horse chestnut’s leaf is divided into leaflets in the way that your
hand is divided into fingers. Hold out the palm of your hand and
spread your fingers and you have a reasonable approximation of the
palmate leaf of the horse chestnut.
The horse chestnuts, or buckeyes, form the only other
major tree group with opposite leaves and branching patterns.
Probably the most familiar species is the Ohio buckeye. Whereas
most maples have simple leaves, the horse chestnuts have compound
leaves. Recall that the ash also has compound leaves. The
horse chestnut leaves, though, are clearly distinguishable from those
of ash because they’re what’s called palmately compound. In
other words, the horse chestnut’s leaf is divided into leaflets in the
way that your hand is divided into fingers. Hold out the palm of
your hand and spread your fingers and you have a reasonable
approximation of the palmate leaf of the horse chestnut.
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Fig. 8 Flowering Dogwood
twig with leaves and fruit
Fig.9
Flowering Dogwood twig showing
flower buds
Fig. 10
Flowering dogwood flowers |
Dogwood
The dogwoods are a family of woody plants that include
a variety of shrubs and the familiar flowering dogwood that reaches
small tree size. With one exception—the alternate-leaf
dogwood—dogwoods have opposite leaves, twigs and branches.
(Nature is replete with exceptions to human-imposed rules and the
alternate-leaf dogwood is a prime example.)
When not in flower the flowering dogwood is, in some
ways, more identifiable with the leaves off than with them on.
This is due to the unique urn-shaped flower buds. Of course the
blossoms will give this tree away almost every time. What may
come as a bit of a surprise is that the showy parts of the flowers are
not petals but so-called bracts. The bract is a regular
structure in flowering plants but is often, or usually, inconspicuous.
Not so in the flowering dogwood.
Sorting it Out
There’s a handy mnemonic
dendrologists use that makes it easy to remember which trees have the
opposite branching pattern. It’s pretty simple and goes like this:
“MAD HORSE.” The MAD refers to maple, ash and dogwood and the “HORSE”
refers to the American horse chestnut, otherwise known as the
buckeye. Remember this phrase and you’ve got all the opposite-leaved
trees covered. (By rights there’s a central term—CAP—in that
mnemonic that represents a family of mostly shrubs but it’s simpler to
leave it out when considering trees.)
Keep in mind that even with
trees that have opposite leaves and branching patterns, by the time
branches have grown to be larger in size often their opposite
counterpart has died off. So even though a tree may inherently have
the opposite branching characteristic, its older branches won’t
necessarily reflect that. Even on small twigs where the opposite
branching pattern is more obvious, one side of the pair or the other
can, and often does, break off from wind or from animal activity and
the like.
Alternates
Of the more than 800 species of
trees native to North America, the vast majority are alternate in leaf
and branching pattern. The oaks, as a group, are as reasonable a
place as any to start in describing these.
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