MEASURING NOTABLE TREES

The Connecticut Botanical Society uses American Forests’ tree measurement system, which produces a single number that we call points. American Forests is responsible for National Register of Big Trees.

The formula simply adds together:

• trunk

**circumference** at 4.5 feet above ground, in inches

• tree

**height**, in feet

• one-quarter of the average canopy

**spread**, in feet.

__Circumference.__ With a tape measure, find the circumference (not diameter) at 4 feet 6 inches above ground level. If the tree is growing
on a slope, measure the 4.5 feet up from the center of the slope, i.e.
not the lowest or highest place where ground meets tree. If branches
begin to swell the trunk at or below 4.5 feet, measure the smallest
circumference below 4.5 feet. If the tree is multiple stemmed and forks
above ground level, measure the smallest circumference below the place
where the stems originate and also measure each stem at 4.5 feet. If it
is multi-stemmed into the ground, measure each stem separately and note
this condition on the datasheet. Convert feet and inches to inches for
the calculation.

__Height.__** **We do not use estimates for trees which are contenders for
largest of their kind. Most of the measurements for this project have
been done with a clinometer (available from forestry supply companies)
which we find accurate to one or two feet in 100. This device, which
currently costs about $150, is held in the hand and the treetop is
sighted through it. A scale visible inside gives height in feet when
the clinometer is exactly 100 feet from a point directly below the
sighted branch (note this is not necessarily the base of the tree
trunk). With a simple calculation it can be used at distances other
than 100 feet. An estimate can sometimes be done by measuring the
tree's shadow, measuring the shadow of an object of known height, and
using the difference between the object's true height and shadow length
as a correction factor to obtain the tree height. This is usually more
accurate than guessing, but only works on sunny days on open sites.
There are various other optical and electronic instruments available
for measuring heights. Use the height in feet for the calculation.

__Average Spread.__ With two people, or by
pinning down one end of the
tape, measure the greatest branch spread from one end of the canopy in
a straight line next to the trunk to the far edge. In the same way,
measure a second spread in a line perpendicular (90 degrees) to the
first line, regardless of canopy size above. The two spread
measurements, in feet, are averaged and divided by 4 for the AFA points
calculation.

For more detailed information, please see this document:
American Forests' Tree Measuring Guidelines.

REPORTING NOTABLE TREES

Information about potentially notable trees in
Connecticut can be sent to gddre@conncoll.edu
or by mail to:

Notable Trees Committee

Connecticut College Arboretum

270 Mohegan Avenue

New London, CT 06320

Please include the name of the tree if at all
possible, the circumference at 4.5 feet above ground, and the name,
phone number and address of someone who will show us the tree if we
decided it merits a complete measurement.