10 Arbor Age / July 2014 www.arborage.com
B y M i c h e l l e S u t t o n
S
tudying tree pruning and its effects on tree stability is
a classic form of applied research — and can be a little
lonely. "Only a few researchers are tackling pruning
right now, and that can be frus-
trating," said Dr. Ed Gilman, professor of
Urban Trees & Landscape Plants for the
University of Florida Environmental
Horticulture Department. Gilman does
a great deal of outreach to commer-
cial arborists to teach pruning practices
based on his applied research fi ndings.
Because he is Florida-based, Gil-
man is acutely aware of the need for
tree pruning that enhances the tree's
ability to survive wind storms. As many
parts of our nation and world continue
to contend with severe storms, his re-
search has application well beyond the
Sunshine State.
Storms, risk, and where to prune
To fi nd out what method of prun-
ing best equips a tree for resisting storm
damage, in 2006, Gilman and his re-
search partners Dr. Jason Grabosky and Dr. Jake Miesbauer
subjected young live oak trees that they had grown since 2001
to winds of 110 mph. They employed a wind generator built
by wind engineers that was specially designed for hurricane
research. (You can see a mesmerizing short video on YouTube
if you search for "Effect of Hurricane-Force Winds on Land-
scape Trees.")
Of the 80 live oak trees in the
study, 20 trees were unpruned, 20 were
thinned, 20 were raised, and 20 were
given reduction pruning. Those that had
been pruned by reduction faired the
best. (Reduction pruning Gilman de-
fi nes as "reducing the length of a branch
or stem back to a live lateral branch
large enough to assume the terminal
role — this is typically at least one-third
the diameter of the cut stem.")
Gilman's research also focuses on prun-
ing as a means of risk management after
a proper risk assessment has been con-
ducted, such as that which the ISA Tree
Risk Assessment Qualifi cation course
teaches. Said Gilman, "Basically, there are
four things you can do after assessing —
do nothing, remove the tree, secure it with
support, or prune it. Our research is about
INDUSTRY INSIGHTS INDUSTRY INSIGHTS
Applied Research
and the
Bottom Line:
Ed Gilman's Work
on Pruning
Structural Pruning: A Guide for the Green
Industry By Edward F. Gilman, Brian
Kempf, Nelda Matheny and Jim Clark
(Urban Tree Foundation 2013).
Part 2 in a series
