When traveling over the State of Maryland, you will find a great variety of tree
species growing. The importance of trees, not only in our landscape but in our
very way of life, is being recognized by more people every day. Residents of the
state show a universal interest in “Big Trees”, and this interest was first
recorded by State Forester Fred W. Besley in 1925 when he compiled the “Noted
Tree List” for Maryland.
Fred Besley, our first state forester, aroused interest in big trees across the
state, and over the years collected measurements and photographs of
distinguished trees of the state. Each year brought new nominations, but in
order to complete the list of all the native species, a more intensive search
was necessary. In 1925, interest in large and unusual trees was stimulated by a
Big Tree Contest. Rules were adopted and prizes were offered to secure as many
entries as possible. Each tree species was classified separately so the small
trees like dogwood would not have to compete with larger trees such as oaks and
maples. At that time, there were no standard rules to measure trees. In order to
ensure fair comparisons of trees, certain measuring procedures had to be decided
upon. Mr. Besley devised the following standards that are still used today:
Circumference in inches + height in feet + ¼ of the average crown spread = total
circumference, or girth, is obtained using a flexible tape measure. It is
usually taken at a point on the trunk 4.5’ above the ground. However, if the
tree has a smaller circumference below 4.5’, due to a burl or protrusion, or
because of a fork in the tree, the circumference is taken below 4.5’ at the
narrowest point on the trunk. This measurement is recorded in feet and inches,
but then converted to total inches for the first part of the formula.
The height, or how tall the tree is, is obtained using a clinometer or laser
hypsometer. This is the most difficult measurement to obtain, and the volunteers
who measure trees for the Maryland Big Tree Program will usually take a number
of measurements from different locations and average them. The average height is
then recorded in a whole number and added to the formula.
crown spread, or distance from branchtip to branchtip, can be done either with
the flexible measuring tape or laser hypsometer. Two measurements are taken; the
first measuring the greatest crown spread, and the second at 90 degrees from the
first measurement. In an open area, this is an easy measurement to take, but in
heavy brush, or in small yards when the tree branches hang over into the
neighbor’s yard, it becomes more difficult and less accurate. The two
measurements are added together and divided by 2 to obtain the average. The
average is then recorded in the formula. However, when calculating the total
points, the measurer must remember to divide the average crown spread by 4 to
obtain ¼ of the average.
A white oak has a circumference of 17 feet, 6 inches. Multiple 17’ x
12” + 6” = 210”.
It has a height of 83 feet.
The longest crown spread is 120 feet. The crown spread at 90 degrees is 96 feet.
120’ + 96’ = 108’.
Formula: Circumference (120”) + Height (83’) + ¼ of average crown spread (108’ x
¼ = 27) = 320 points
In this example, the white oak would be considered an “average” big tree. The
State Champion currently (2010) is at 392 points. We have over 30 white oaks in
Maryland larger than 320 points.
While obtaining the height of the tree is the most difficult (and the most
inaccurate) measurement, obtaining the circumference has the most special rules
and exceptions. One particular rule to remember is that a tree with heavy vines
growing up the trunk cannot be accurately measured until the vines are cut
and/or removed. For obvious reasons, trees with poison ivy vines should not be
attempted until those vines are removed.
The Maryland Big Tree Program, sponsored by
the Maryland Association of Forest Conservancy District Boards, provides a free
service to measure big trees in Maryland.