Determing Age of Street Trees (OT?)
  Apr 28, 2004 08:15 PDT 

Hello, ENTs,

I am new to the list, and have been reading the last few weeks of posts with
interest, hoping that you may be able to give me some insight into a project
that I have been hoping to start.

Although I have seen many references on this list to the age of trees in
forested areas, I am noticing that you place more of an emphasis on tallest
and biggest trees. My interest is somewhat different, in that I would like
to find some way of estimating the age of trees not in a forest ecosystem,
but in a suburban setting, specifically along historic roadways, or at homes
near those roadways.

I am a county park naturalist in Camden County, New Jersey, and although not
a tree expert, I have an interest in the old trees which can be seen along
some of the roadways here in the county. Many of our major roads have been
aligned along the same path for over 300 years. By the time of the
Revolution many of these roads had already been in use for almost 100 years.

I am planning the route of a bus tour in which we will attempt to learn
about the history of Camden County and portions of Burlington County through
the interpretation of natural and cultural history clues.

I would like to be able to point out and talk about specific trees along the
route of an interpretive bus tour I am planning as evidence of the length of
use of those roadways.

Along many of these roads I have been looking to include a number of large
trees with the hope that there might be a non-invasive method of estimating
their ages. Many of these trees are on private property close to the road.
I'm sure most folks would let me measure them but would not consent to a
forester taking core samples, so I was intrigued when I came across a
formula, said to be developed by a tree expert (M.W. Staples of Kent. Ohio)
that was being promoted by the NJ Community Forestry Program. This formula
placed a number, called a multiplier or growth factor, to different species
of trees, which, when multiplied by the dbh would give an age estimate for
an individual tree of that species. This list that I obtained had
multipliers for 45 species of trees.

My questions are this:

How much credence can I give to this formula? What kind of consensus might
there be on the accuracy of estimating age without taking a core sample?
Are there major differences of opinion between foresters and arborists about
such a formula?

This formula came with a disclaimer that the figures were for trees in a
forested situation, so if there is any consensus about the original formula,
is there a way to adapt that formula to fit the need for interpreting the
age of non-forest trees? Has any research been done as to the differences
in growth rates for forested vs. non-forested individuals of the same

There are many people who may never get to some of the forest areas you have
been mentioning in previous posts, but they do pass by some pretty amazing
examples of tree survivors in their own suburban communities. If there were
a way to determine with a known degree of accuracy the age of trees they see
all the time, along their streets, it could be an important method of
imparting a sense of our county's historic legacy that often is hidden among
the shopping centers and suburban developments of the modern era.

Thanks for any information you can offer me. I assume that this may be
somewhat off-topic, but I am hoping that it is not too far off for your
replies. If you know of any another groups for which this query might be
even more appropriate, I would appreciate that information as well.

Dave Orleans
Camden County Park Naturalist
RE: Determing Age of Street Trees (OT?)   Robert Leverett
  Apr 28, 2004 10:37 PDT 


     Welcome aboard. Actually, you've not strayed from our interests at
all. We have several dendrochronologists on the list that deal
constantly with tree ages. At least a dozen of us have considerable
experience in estimating tree ages for both open and forest-grown forms
and we'd be delighted to discuss the topic with you for as long as you
wish. I'll start the ball rolling by observing that no formula of which
I am aware has been successfully proven to relate diameter to age. The
oldest trees that most of us date are seldom the largest. Having said
that, there are also some very old large trees, so estimating age should
not discount size altogether. However, as a general rule, we steer clear
of relating age to size.

    What is most helpful is a knowledge of maximum longevities and where
those longevities are achieved and how each species changes shape and
bark texture over time. This knowledge can often get you in the ball
park in terms of recognizing an old tree, even if you are 100 years off
in the actual age (250 versus 350). However, some species show their age
much better than others. Additionally, in wet areas, many trees age
prematurely, so that you have to be able to distinguish signs of aging
due to stress as opposed to actual age.

    What would be helpful for us would be a digital image of the tree
for which you want age estimates. In addition, please give us its
species, girth, and the conditions in which you find it growing. It
would be interesting to examine the range of age estimates you receive
from the experts. Admittedly a digital image may leave a lot to be
desired, but without a visual, we're all dead in the water.

    What is especially important in placing a high age on a tree is how
far up the trunk and onto the limbs old bark patterns go. If the bark
lookd mature near the base of the tree but is young aloft, great age is
almost impossible. If the tree is large then its size then correlates to
favorable growing conditions.

    John Knuerr recently purchased a digital camera with an 8-megapixel
resolution. John intends to profile a number of species over time,
searching for the limits. So your request comes at an opportune time.
Maybe a number of us can get behind you. That's what ENTS is about.

    Again, welcome aboard.

RE: Determing Age of Street Trees (OT?)   Robert Leverett
  Apr 28, 2004 13:33 PDT 


   In terms of the disciplines that recognize tree aging
characteristics, we need to add a couple more to the two you listed:
dendrochronologists and forest ecologists. In terms of the scientific
disciplines that recognize aging characteristics, they're at the top of
my list.

   Some urban foresters rank high in estimating tree ages based on
observation of characteristics. Contrary to the public's perception,
non-urban foresters lag the other groups. They typically do not
specialize in studying very old trees. Their focus is on younger trees
up to what they believe to be the peak of economic maturity, which for
most eastern species is usually 120 years or less. Arborists vary
greatly in the expertise they exhibit in estimating tree age. Arborists
like Will Blozan and Mike Davie, and a few others, are exceptional. But
Will was a science technician with the GSMNP for several years. He cored
countless trees and has an eye like a hawk.

   Four splendid scientists on our lists that have a wealth of
experience aging trees are Lee Frelich, Charlie Cogbill, Dave Orwig, and
Neil Pederson. Charlie keeps track of all legitimate age data. Come to
think of it, Robert Van Pelt needs to be added to the list, although his
focus is more to the west.

   In addition to those above, I would not want to overlook naturalists
like Dale Luthringer who ages a fair number of trees. Finally, one of
the co-founders of ENTS is Dave Stahle, Director of the Tree-Ring
Laboratory at the University of Arkansas. Dave let's his doctoral
student Matt Therrell feed him important information from the list, but
we can ask him specific questions. Still others with a lot of experience
in dating trees include Tom Diggins, Bruce Kershner, Colby Rucker, John
Okeefe, and Larry Winship in no particular order. Come to think of it,
we're swimming in talent.


Re: Determing Age of Street Trees (OT?)   Colby Rucker
  Apr 28, 2004 13:49 PDT 

Bob, Dave,

Including trees in the cultural history of an area is most rewarding, in
that the trees tell much about the past use of the land, whether forest,
agricultural, residential, etc., and the cultural aspects of the area tell
much about the use, appreciation, retention, selection and care of the

As one learns more about the area, the life of each tree becomes more
apparent. This is a gradual process, and one must avoid the temptation to
assign arbitrary ages to trees too freely. Too often, some age, say 350 or
400 years, is assigned to a tree simply because it sounds good, encourages
recognition or protection, and increases tourism. In time, that age becomes
thoroughly accepted, and the tree's age becomes adjusted as "436 years," or
something, as if the first claim were absolute.

I've been asked the age of a tree by many owners of trees, and invariably
confuse them by turning my back on the tree and surveying the immediate
neighborhood. The first clue to a tree's age is its natural environment and
the age of what surrounds it. If it's a non-native, when was the species
first introduced? When was the species popular? Why was it planted there?
What is the age of the nearby structures? How has the property changed?
How have road alignments changed? Did the tree grow in an open pasture, or
at the edge of a woods?

Once you know the local history in the time frame in which the tree has
existed, the structural form of the tree makes more sense, and you can make
some assumptions as to how fast the tree grew. Depending on the species and
the competition, the trunk may have been three or four feet thick at age 75,
or less than one foot. Twig growth patterns give some idea of how long it's
been nearly the same height. Certainly, as Bob says, bark is a useful
indicator of age, but it takes a good deal of experience to recognize how
bark patterns not only change with time, but are influenced by the immediate
environment. How long does it take a black oak to turn white?

Although some trees are undoubtedly very old, it's often surprising how many
are recent interlopers masquerading as associates of the early colonists.
Enough trees are cut down each year to permit some ring-counting, and
anything over a hundred years is unusual. A ring-count of a lower limb can
be most revealing. A red oak eight feet thick had limbs 140 years old. A
review of old photographs may show the tree as a mere sapling or completely
absent. Rehder's manual may show that the species wasn't introduced until
later than supposed.

You may find measurements for famous trees, and that may be helpful, but if
you find enough measurements, you'll probably find that some of them suggest
the tree has been getting smaller, not larger. If the circumference was
taken six feet up, that height was probably a guess added later, and
circumference may have been calculated by someone pacing the maximum
diameter. Still, taking very careful measurements now can tell much about a
tree even several years from now, and it's surprising how rapidly your
measurements become a record of over fifty years past.

Everything considered, the absolute numerical age of a tree is of little
importance. What is important is understanding how a tree can testify to
its interaction with its surroundings, both the natural environment and
different cultural times. Anything that moves people from their infatuation
with mere numbers would open new doors and would be a great step forward.


RE: Determing Age of Street Trees (OT?)   Adam Van Buskirk
  Apr 29, 2004 09:53 PDT 

    I'm also new to the list, and interested in large and old open grown
specimens.   I have found an interesting formula developed by British
Forestry for estimating the ages of trees were coring is not possible and/or
the tree is hollow.   Their system would not be usable here, since it it
obviously dependent upon specific information gathered on British sites and
species, but I was wondering what the experienced estimators thought about
the general approach.

Information Note - Investigating the Age of Large and Veteran Trees in Britain$FILE/fcin12.pdf

I actually suspect that it is very inaccurate, but at least they don't
define a species maximum age as the oldest age that it can reach while
retaining a solid trunk. I also appreciate their respect for short trunked
mulitstemmed trees, "phoenix" trees that crumble and sprout again, and all
the interesting variations sometimes overlooked by American champ tree lists
and enthusiasts.

RE: Determing Age of Street Trees (OT?)   Robert Leverett
  Apr 29, 2004 10:33 PDT 


Most of us in ENTS are interested in age ranges for all forms of
trees. However, good data are hard to come by for open-grown trees.
Isolated trees and trees growing on property boundaries seldom catch the
attention of scientists who are studying forest processes. It is
interesting to learn about the added interests of the British.

With respect to the focus of American big tree enthusiasts, most of us
in ENTS agree that the focus has been far too narrow and hopefully we
can expand the types of lists we maintain. Interestingly, we have a
broad range of opinion about the direction we should be moving with
respect to the lists we promote. I have a tendency to go overboard.
Others prefer to stay traditional and simple. I think the winds of
change are blowing form them though.

   In adopting new formulas to rank big trees, we need to rethink the
root assumption made for the current 3-measurement process. Some of us
have been doing that. I'd put Colby Rucker at the head of the list in
terms of new ideas and the depth of thought. I, for one, would love to
see Colby share his thoughts on improvements to the big tree formula.
We've discussed the topic before, but the e-mails are very scattered.
Maybe Colby could bring us up to date. Colby?