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For many arborists, palms are a mystery. We aren't sure what to make of them.
They don't fit easily into the basic categories we normally use for thinking
and talking about trees. Arborists, in fact, sometimes question whether a palm
is a tree at all.
The confusion is understandable and centers on the definition
of the word "tree." Botanical authorities sometimes refer to palms as trees
and, at other times, they do not. Dictionaries don't help much, either. Some
dictionary definitions specifically include palms, while others exclude them.
Most definitions, however, do not refer specifically to palms. Instead, they
direct us to a series of other broadly defined terms that leave us scratching
our heads and still wondering.
The problem is that the word "tree" is not a
strict scientific term. Rather, it is an Old English word derived from a deep
and varied history. Its primary meaning comes from common, everyday usage and,
as such, is flexible and hard to pin down. Whether we refer to palms as trees
or not is subjective. Either way, we'd be right.
To add to the confusion, many
plants that are called palms and that look more or less like palms are, in
reality, not palms. The most common example is the sago palm, which is not even
closely related to true palms. Sago palm is a name given to certain species of
cycad (Cycas spp.) which, despite their appearance, are more closely related to
conifers than to palms. Other examples of such misnamed plants are dracaena
palm (Cordyline australis), traveler's palm (Ravenala madagascariensis), and
bottle palm (Nolina recurvata).
Most of what we know about palms, however, is
not so confusing. In particular, our basic knowledge concerning the biology and
structure of palms is clear, straightforward, and objective. So let's begin by
looking at the place of palms in the plant kingdom and especially at their
relationship to the kinds of trees we as arborists are more accustomed to
working with.
There are two primary ways of looking at the biological
relationship between palms and other kinds of trees. One is in terms of
evolution and the system of plant classification that is based on evolution.
The other is based on biological structure. First we consider evolution and
classification.
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International Society of Arboriculture
