THE VIEW FROM THE TOP

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THE VIEW FROM THE TOP
Arboretum Arborists Bring Plant Care to the Canopy
Jon Hetman, Communications and Stewardship Officer
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reasons. “We’re a well-balanced team,” Bob says of his arborist
cohorts. “We all do everything and rotate responsibilities. On
more complex jobs, like a tricky removal, we gravitate to our
own particular strengths.”
In an urban landscape like the Arboretum, trees may
be affected by an array of human and natural disturbances,
Richard Schulhof
Jon Hetman
arge, inviting trees reaching skyward may spark in
us an instinctive urge to climb. Though this may be
tempting, the Arboretum asks visitors to admire its
trees from the ground, to protect what are essentially living
museum objects. Consider also that without proper training,
supervision, and equipment, tree-climbing can be a very
dangerous activity. To protect life and limb of trees and treelovers alike, ascending the canopy is best left to the experts—
the Arboretum’s arborists.
The arborists at the Arnold Arboretum—head arborist
John DelRosso, Bob Ervin, and Kyle Stephens—share nearly
40 years of combined experience in arboricultural care, and
thousands of hours accrued in the treetops. Their individual
career paths include work with commercial tree companies,
golf courses, and even Central Park in New York City. Here
they work collectively most of the time, cycling through the
collection and keeping one another within earshot for safety
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Left to right, John DelRosso shows the ropes to
interested young visitors at an Arboretum event; Kyle
Stephens removes a dead limb from a cedar of Lebanon
(Cedrus libani) near the Hunnewell Building; and Bob
Ervin ascends an accession of cucumber magnolia
(Magnolia acuminata).
ArnoldArboretum
Arboretum
Arnold
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the LMP is that it apportions more time for everyone on the
crew to work in lower priority zones. “As arborists, our work
was much more defensive previously,” says John. “We mostly
focused on situations needing our immediate attention.
Now we spend more time identifying potential problems
and taking care of them before they become hazardous.
As a result, we generally work less defensively because the
collection as a whole has improved in condition.”
Proper pruning can provide many advantages to a tree,
but is only performed with a specific purpose in mind. “Every
leaf is feeding the tree,” Kyle explains. “We try not to cut
more than is necessary for the
health and well-being of the
plants here. Unlike arborists
working commercially, we have
the luxury of knowing we’ll
return to these same plants
on a regular basis, so some
work can wait.” While they are
skilled in tree removal, they
take great pains to preserve
trees as valuable individuals
in the living collection. “Many
of the trees we work on are
significant because of their age,
origin, or history,” says Bob.
“We want to help them thrive
for as long as possible.”
Since the LMP was put
in effect, the arborists estimate
they spend about 90% of their
time climbing, so they value
opportunities to spend time
on the ground. One way they
do this is by pitching in on
larger projects, like the current
Bradley Rosaceous Collection
renovation. They also participate in the Arboretum’s horticultural training program with
Norfolk Agricultural High School students, and the Arboretum’s Hunnewell Interns spend a week with the arborists
each summer. As with many other members of the staff, they
also teach an occasional Arboretum class, including tree
identification, pruning, and pest management offerings. “A
fun part of our job is interacting with the public,” says Kyle.
“It’s great to talk about what we do and play a role in the
education here. It’s important, though, for safety sake, to wait
to engage us when we—and any tree parts we may be removing—are safely on the ground.” e
Jon Hetman
both above and below ground. Like doctors rigged with
ropes and harnesses, arborists provide continual care aimed
at improving a tree’s prospects for survival. Timing and
methods of treatment depend on the species of tree and
the purpose of the work. To determine the best practices,
a thorough knowledge of local species and environments
is essential. This task increases in complexity at the
Arboretum, where familiar native species are grown sideby-side with exotic species from all over the world, and the
cultural needs of these plants aren’t always immediately
understood. Toward this end, arborists are continually
learning from their experience
with trees in the collection,
and applying their knowledge
to new challenges as they are
encountered in the landscape.
Guiding their efforts—and
indeed the work of the entire
horticulture staff—is the institution’s Landscape Management Plan (LMP), currently in
its third edition. The LMP provides a pruning calendar based
on intensity of needs and the
priorities of each of the Arboretum’s collection zones. Some
zones require attention multiple
times a year, while others may
need work once every few years.
“Pruning gets scheduled based
on growth habits, seasonal
access issues, and the individual characteristics of a species,”
remarks John. “For example,
some trees tend to sucker if they
are pruned in spring rather than
fall. On the other hand, it can
be difficult with ashes (Fraxinus
spp.) to tell the difference between live and dead twigs in
winter, so these are pruned during the growing season. Trees
grow slowly, so we often find the right approach through
years of direct contact.”
The LMP also facilitates a great deal of collaboration
in collection care, and the arborists often work closely with
the Arboretum’s skilled group of horticultural technologists.
“Our hort techs are a great resource to gain information on
the condition of trees in all parts of the Arboretum,” explains
Kyle. “Advice and consultation helps us keep up with the
demands of all parts of the collection.” Another advantage of
Spring/Summer 20117