King of the Forest: Chestnut trees face extinction unless measures

TECA Chestnut Feature_TECA_0114_ 12/31/13 3:43 PM Page 12
of the
Chestnut trees
face extinction
unless measures
are taken
Story by Debra Gibson Isaacs
Photographs by Robin Conover
r. Gregory Weaver is too young to
remember the American chestnut
when it was the kingpin of trees —
the most common and important tree
in the eastern United States, a forest giant,
often growing up to 100 feet tall and 5 feet
in diameter. But chestnut blight, technically
Cryphonectria parasitica, was accidentally
imported from Asia, and by the end of the
1930s, the Tennessee chestnut forests were
largely destroyed. Today, though, Weaver is
one of the people determined to breed a
blight-resistant cultivar of the American
chestnut and return the tree to its rightful
place as “king of the forest.”
The tree earned its exalted title because
of its many attributes.
“Chestnut trees grow all the way up to
Canada,” Weaver says. “They are resistant
to 30 degrees below zero
and can tolerate 100-degree
Dr. Greg Weaver stands next to a dead chestnut trunk in the Great Smoky Mounheat and go without rain.
tains National Park. The tree probably died in the 1930s. Its large stump, measuring
When harvested, chestnut
15.5 feet in circumference at chest height, is still standing because of the rot resistwood is rot-resistant,
ance of chestnut. Photograph courtesy of Dr. Greg Weaver
lighter than oak but strong
for its weight. It has a good combination
of lightness, strength and rot-resistance.
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The chestnut also does not
require the use of wood
In addition, the trees support wildlife from black
bears to turkeys, songbirds,
squirrels and chipmunks.
The loss of chestnuts, a tasty
and nutritious food source,
is largely responsible for the
20th century decline in the
number of black bears. Scientists don’t even know the
full impact of the loss of the
chestnut tree — considered
one of the worst ecological
disasters of the century —
because ecological science
was too primitive in the
1920s and ’30s. But, as
Weaver notes, “You can’t
erase 25 percent of a forest
and not have an impact.”
Members of the Tennessee Chapter of the American Chestnut Foundation (TACF) present Dr. Gregory Weaver with the National American Chestnut Foundation Volunteer
A lifelong quest
Service Award for his efforts with the organization. From left are Clint Neel, Vicki Turner,
Weaver’s journey to help Sean Fisher, Paula Phelps-Weaver, Dr. Weaver, Tennessee Chapter TACF President Joe
restore the American chest- Schibig, Jack Torkelson and Tim Phelps. Below, orange blight fungus grows on a damnut actually began more than aged chesnut tree. Photograph courtesy of Dr. Greg Weaver
five decades ago, although
“Daddy knew a lot about trees,” Weaver recalls, “and he
he didn’t know it then. At the time, Weaver was just relishwould tell us about them. There were a lot of big chestnut
ing Sunday afternoon walks on the family farm with his
stumps on the farm, and he would tell us stories about how
dad, Arles, mother Joyce and brothers Anthony and Tom.
important the chestnuts once were.
“Daddy remembered eating the nuts and how one of the
signs of toughness as a young man was to stomp open the
chestnut burrs with your bare feet. He could do it. Dad remembered watching the trees die, the tops dying first until
they were just chestnut ghosts. Chestnuts are rot-resistant,
though, so the trunks and stumps stood many years.”
Stumps were still scattered around the family farm
when Greg left for college for a degree in forestry. He didn’t like the idea of cutting down trees, so that degree soon
changed to premed followed by medical school and a specialty in radiology. Weaver never lost his love of forests
and trees, though, most especially the chestnut.
In 1995, Weaver — by then a respected radiologist with
a farm of his own — found a brochure about The American Chestnut Foundation (TACF) and the organization’s
special breeding process. He joined immediately and went
to its fall meeting.
“My knowledge of what was going on in regard to the
chestnut was limited,” Weaver says. “I knew the history of
the tree, but I didn’t know where the science was. I found
out there were a wide assortment of people — scientists,
Januar y 2014
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academics, people like me, industrial
foresters — who are serious about
restoring the American chestnut. This
wasn’t a theory. They were going to
do this.”
Weaver is a doer. His idea of
leisure is to haul rocks and build
stately stone fences at the entrance to
his farm on Leipers Creek Road just
outside of Nashville. The goal of developing a stronger, blight-resistant
strain of the tree intrigued him, although he knew prior attempts to
breed blight-resistant trees in the
mid-1900s were unsuccessful.
Weaver soon planted TACF-provided chestnut seeds on his farm.
“These were pure American chestAbove, Dr. Hill Craddock and his University of Tennessee at Chattanooga crew
nuts, so we knew they would get a
grade blight resistance and assess physical characteristics of American chestblight infection and ultimately die,”
nut trees in Greg Weaver’s Williamson County orchard. The trees had been inhe says, “but I needed to learn the
proper technique of planting the trees oculated in June 2012 with two strains of chestnut blight. Photograph
courtesy of Dr. Greg Weaver. Below, a tree injected with the blight is marked.
and how to care for them. An intermediate step for my chestnut-growing
grow the generations of trees proximal
efforts was to plant hybrids — trees that are partially
to the ultimate goal.”
blight-resistant and used to successively concentrate blight
A recent addition to Weaver’s orresistance in their offspring. A lot of my work has been to
chard are chestnut saplings that have already been crossbred. The trees —
F3B3 chestnuts as they are known
among TACF members — are 15/16
American chestnut and 1/16 Chinese
“We want an American phenotype
Dr. Weaver
that is a forest canopy tree,” he says.
“Before the blight, it was common for American chestnuts
to be 120 feet tall when fully matured.”
But breeding a tree isn’t like other endeavors where you
put the right ingredients together and create the product
you desire. The breeding program has to go through six
generations to reach the 15/16 American gene fraction, with
the 1/16 for Chinese origin blight-resistance.
“Along the way you select American chestnut traits,”
Weaver says. “Only about 8 percent are blight-resistant
enough to propagate to the next generation. We’re still in
testing. We will have to see how they grow.”
A microcosm of a bigger movement
Weaver can see some of that growth in his own chestnut orchard set high on a hill at his farm (chestnuts grow
best on the top of hills). Each year, he has planted more
“It’s important to keep planting,” Weaver says. “Some,
the deer get; some, drought gets. Small rodents are a big
problem. Voles, for instance, eat the plant roots and essen-
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tially amputate the trees. The aim is to increase the number over time.”
In this regard, Weaver says he and his
fellow association members are farmers.
“We’re growing a crop for a charitable
cause and for future use, but we’re still
farmers. We are subject to all the same
problems that farmers are subject to.”
Drought is particularly rough on the
trees, according to Weaver. He has designed
a system to collect rainwater in huge barrels
and then distribute it with hoses so the trees
can be watered when there isn’t enough
rain. The system can capture 13,000 gallons
of rainwater and does not require electricity. It was a significant development beSeeds from American chestnut trees backcrossed with Chinese chestnuts
cause otherwise Weaver had to haul water
begin growing in tubes. As they grow into saplings, they will be injected
in 5-gallon buckets a half a mile up the
with two strains of chestnut blight fungus to test their resistance. Trees
steep hill.
with good resistance will be used in future crosses. Photograph courtesy
After years of protecting the seedlings
of Dr. Greg Weaver
from deer and other animals, keeping the
constructing an informational display about chestnuts that
young trees watered and building fences and watering syshe made from recycled chestnut lumber. The display is
tems, last summer members of the Tennessee chapter of
currently on extended loan to the Science Department at
The American Chestnut Association came to poison the
Volunteer State Community College in Gallatin.
very trees Weaver had worked so hard to grow.
“This work is very important to me,” Weaver says, “but I
They deliberately infected Weaver’s trees with two viruam a small part of the total puzzle. We need everyone to
lent strains of Cryphonectria parasitica. Then the trees
were graded according to how they responded to the infec- volunteer, to do something. You don’t have to have a farm
to participate. It is a huge commitment, and it is gratifying
tion. Weaver said most of his trees were killed. “I have a
to see people across the spectrum pulling together.”
few left,” he says, “and they will become parents for the
Now assisted by memnext generation.”
bers and volunteers such as
This process is being
Weaver in 16 state chapduplicated across the naters, TACF is planting
fter the chestnut blight killed entire forests of trees, the
tion. One of the leaders narestoration chestnuts in setrunks still stood tall for decades. In 1936, some farmers
tionwide is the Hill
lect locations throughout
in Indiana decided to turn the tragedy into triumph, acCraddock, a professor at
the eastern United States.
the University of Tennessee
cording to a December 2013 article in Rural Electric maga“My father’s generation
at Chattanooga and one of
zine. The farmers used the trunks to build an electric
chestnut trees in the
the world’s pre-eminent
distribution system. Tall, strong and rot-resistant, the trunks
Weaver says. “My
chestnut scientists. Some
were perfect poles, and soon, aided by a $100,000 loan
is doing the
300 people in Tennessee
from the Rural Electrification Administration, an electric
work to get them back, but
and 6,000 nationwide are
cooperative was born and people who never had electricwe won’t know if we were
doing their part to help reity before could now flip a switch and light their homes.
successful for 400 years.
store the tree.
The first pole was set on
My hope is that my chilIn October, Weaver was
Feb. 12, 1936. The last one was
dren will see the chestnuts
honored for his work with
taken out of service in 1997.
introduced back into the
a Volunteer Service Award
The American chestnut’s repuforest.”
from TACF. The award
tation for being strong and rotThe website for the
recognized his service as
resistant remained true even
American Chestnut Foun(past) president of the
after the trees’ deaths.
dation is You
Tennessee chapter and his
These tree trunks were used
can contact the Tennessee
volunteer work growing
as poles throughout the counChapter of TACF via email
an orchard, giving lectures
try. The trees were bought and
at [email protected]
and presentations and
sold in Tennessee and became
an integral part of electrifying
the nation.
Januar y 2014