www.arborage.com Arbor Age / April 2014 19
Leaf arrangement
Leaf arrangement is a topic that can
be challenging to new tree identifi ca-
tion students, as some species' leaves may
seem to have no pattern. But some minor
study and attention to detail can help dis-
tinguish the different patterns and terms
used to separate one species from another.
Leaf arrangement refers to the pattern in
which the leaves or needles are attached
or "arranged" on the stem or twigs, and
can often give the identifying party an
excellent clue as to what tree species they
should be considering. Leaf arrangement
is typically referred to as one of three
types: whorled, opposite, or alternate. A
whorled leaf arrangement will have mul-
tiple leaves around the stem at the same
spot; an opposite arrangement will have
two leaves on either side of the stem at
the same location; and in an alternate ar-
rangement the leaves will be "staggered"
or alternating on either side of the stem.
Buds
Although buds may seem to be a topic
that won't help with tree identifi cation,
they can actually be quite important. Tree
identifi cation in winter, or when leaves
are simply not present, can be quite chal-
lenging; and knowledge of the form, shape
and structure of different species' buds can
be quite helpful in this regard. Obviously,
the bud arrangement is going to fall into
the same categories as the leaf arrange-
ment previously discussed, but particular
bud characteristics such as scale location
or bud shape are very useful and can iden-
tify individual species once known and
understood.
Pith
This identifying characteristic may not
always be easily seen, but when it is, a good
data collector will take full advantage of it.
The pith is the interior wood structure of
a twig on or from a particular tree, and can
also offer information of value to the iden-
tifying arborist. Although, in many cases, the
twigs may not be readily available, or their
pith all that distinctive, trees such as a walnut
and its pith, which has multiple small cells
or chambers, are quite easily identifi ed in
this manner.
This close-up of an alder shows some of the information that can be gathered about a tree's
leaves and fruit that can help with identifi cation.
Although identifying conifers can be more challenging, close examination of needles and cones
can present clues to determine the tree's identity.
All photos by Michael "House" Tain
