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05/05/2004

One Big Tree

Last week I discussed the bringing back of both the whooping
crane and memories spurred by reading Ralph Kiner’s new book.
I cannot bring back a memory of any past April in which the
blooming bushes and trees have been more beautiful in our neck
of the woods in New Jersey. The large magnolias, cherries,
dogwoods and flowering crab apple trees have been absolutely
magnificent. Speaking of trees, one memory from my childhood
is that of my mother telling people that, at the age of three, I
could recite Henry Wadsworth Longfellow’s “The Village
Blacksmith” by heart. Today, I only recall the lines

Under a spreading chestnut tree,
The village smithy stands.
The smith, a mighty man is he,
With large and sinewy hands ……………

Until this week, I had never given any thought to Longfellow’s
use of a chestnut tree in the poem. Actually, there’s a pretty
good chance that you’ve never seen a chestnut tree, at least an
American chestnut tree. In Longfellow’s time, back in the
1800s, fully a quarter of the woodlands in the eastern United
States were populated by American chestnuts. This hardwood
tree grew to heights of up to 100 feet and trunk diameters of five
feet were not uncommon. The crown of an American chestnut in
the open can spread a hundred feet. Longfellow must have been
inspired by one of these truly “spreading” giants. This was one
big tree, comparable to the redwoods in California. Like the
redwood, the American chestnut was prized as a source of
sturdy, rot-resistant lumber.

Those chestnuts roasting by the fire today are likely to be Asian
chestnuts because, like the whooping crane, the American
chestnut was brought to the brink of extinction. During the
twentieth century, over three billion American chestnuts died!
The culprit is chestnut blight, caused by a fungus known as
Cryphonectria parasitica (let’s call it CP for short). As with so
many problems today, West Nile and AIDS, for example, CP is
an alien species that was imported to our shores. In CP’s case, it
is thought to have stowed away in a shipment of Japanese
chestnut trees ordered by a Long Island nursery in the late 1800s.
Mail orders for cuttings from these trees spread CP from Maine
to Mississippi.

I learned of the plight of the American chestnut from the article
“Return of the King of the Trees” by Karen Wright in the May
issue of Discover magazine. The article deals in part with the
work of Gary Griffin, Professor of Forest Pathology at Virginia
Polytechnic Institute. For additional information, I visited the
Web site of The American Chestnut Cooperators’ Foundation
(ACCF), run by Lucille Griffin (Gary’s wife, daughter or
sister?). The ACCF is a nonprofit foundation “dedicated to
restoring the American chestnut in our Eastern hardwood
forests.” Comparing the task of bringing back the whooping
crane to that of bringing back the American chestnut, for
relatively quick gratification I would join the whooper people.

Cranes can breed more cranes in a few years but to see whether
you’ve been successful in combating the chestnut blight takes
decades. In fact, chances are that you won’t live long enough to
really know how successful you’ve been. Trees are not rapid
growers. A tree must be at least seven years old before it starts
making nuts and there’s no point to testing a tree for blight
resistance before it’s five years old. The blight causes rapid
growing deep cankers that kill tissue and cause the tree’s demise.
On a blight-resistant tree in a blight-infested area, cankers still
form but they are superficial and slow growing and the tree
survives. However, these slow growing cankers can change into
the fast growing destructive type; hence the problem that, many
years after you think you’ve been successful in beating the
blight, it may win out in the end.

So, how to beat the chestnut blight? The American chestnut
itself is trying to wage its own comeback. New shoots sprout
from stumps or old root systems of trees than have fallen to the
blight. Unfortunately, the CP doesn’t go away but sticks around
in the old roots and comes back to attack the new shoots.
Thankfully, there are the rare chestnuts that still stand, even in
heavily blight-infested areas. The ACCF is trying to bring back
the American chestnut by raising and distributing seedlings from
nuts taken from these seemingly blight-resistant trees. The hope,
of course, is that the offspring of these trees will also be blight-
resistant.

Researchers aren’t just hoping that propagation of blight-resistant
trees will do the trick. There is a virus that infects and goes after
the CP fungus. This “hypovirulence” is being used in the blight
fight. The approach is to inoculate the slow growing cankers on
blight-resistant trees with the hypovirulence. Back in 1980,
branches from three resistant trees were grafted onto sprout
clumps and in 1982 and 1983 the first cankers were inoculated
with hypovirulence. These grafts are thriving and have been
producing nuts for a decade, even though surrounded by non-
resistant trees that keep getting killed back by the blight. The
largest is now over 60 feet tall and 20 inches in diameter “at
breast height” with few branches killed by the blight.

The first approach to solving the blight problem was
crossbreeding, begun back in the early 1900s. In this approach,
man steps in to modify the normal pollination process. The
American chestnut has male and female flowers on each tree. A
tree can’t self-fertilize and the pollen from a male flower must be
transported, normally by wind and insects, to a female flower on
another tree. What the breeders do is to place bags over the
newly emerged female flowers of the “mother” tree, wait a week
or so and then fertilize the bagged flowers with pollen taken from
the male flowers of the “father” tree. They do this by misting the
female flower and either painting it with the pollen on a brush or
by dragging a cluster of male flowers across it.

By keeping careful track of the bagged flowers, the breeder can
cross the American chestnut with the more blight-resistant Asian
varieties or, the ACCF approach, with other blight-resistant
American chestnuts from various areas. The nuts harvested from
the bagged flowers can then be used to seed the new crossbreed
hybrid chestnut. As noted, crossbreeding of Asian and American
chestnuts began back in the early 1900s, when the extent of the
blight devastation was realized. While the crossbreeds may have
better blight-resistance, they are much smaller trees than the pure
American chestnut and have trouble competing in the forests
with other trees such as the maples, beeches, ashes and oaks.
Accordingly, “backcrossing” the hybrid Asian-American trees
with the most blight-resistant American chestnuts has been going
on. This approach tries to keep the blight-resistance genes of the
Asian chestnut in a hybrid having more of the characteristics of
the American variety.

The cross- and backcross-breeding to obtain all kinds of mixtures
of the traits of the Asian and American varieties takes
generations of trees to achieve. Hopefully, at least one of the
varied approaches will succeed and the country will once again
have billions (or at least millions) of these giant trees covering
the forests of the eastern United States. The Discover article has
a picture of an 88-foot-tall American chestnut in Olympic
Memorial Park in Tumwater, Washington. This is the largest
healthy American chestnut in the country, grown in the West, far
from the range of the blight in the eastern part of the country. To
really appreciate the size of these trees, take a look at another
picture taken circa 1920 in the article. It shows a man (seated)
and four women standing at the base of an American chestnut. I
measured the height of the women in the picture and, assuming
they were only 5 feet tall, I calculate the diameter of the tree at
seven and a half feet. That’s one humongous tree!

I’ve just looked up the full text of “The Village Blacksmith” on
americanpoem.com. It’s rather long and there’s no way that at
the age of three I would have known the whole thing by heart. I
suspect that all I knew were the lines I quoted and that my
mother had overstated my capabilities, as mothers are wont to
do. Happy Mother’s Day to all you mothers out there! And let’s
hope those “mother” American chestnut flowers produce
children that will live long, blight-free lives.

Allen F. Bortrum



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Dr. Bortrum

05/05/2004

One Big Tree

Last week I discussed the bringing back of both the whooping
crane and memories spurred by reading Ralph Kiner’s new book.
I cannot bring back a memory of any past April in which the
blooming bushes and trees have been more beautiful in our neck
of the woods in New Jersey. The large magnolias, cherries,
dogwoods and flowering crab apple trees have been absolutely
magnificent. Speaking of trees, one memory from my childhood
is that of my mother telling people that, at the age of three, I
could recite Henry Wadsworth Longfellow’s “The Village
Blacksmith” by heart. Today, I only recall the lines

Under a spreading chestnut tree,
The village smithy stands.
The smith, a mighty man is he,
With large and sinewy hands ……………

Until this week, I had never given any thought to Longfellow’s
use of a chestnut tree in the poem. Actually, there’s a pretty
good chance that you’ve never seen a chestnut tree, at least an
American chestnut tree. In Longfellow’s time, back in the
1800s, fully a quarter of the woodlands in the eastern United
States were populated by American chestnuts. This hardwood
tree grew to heights of up to 100 feet and trunk diameters of five
feet were not uncommon. The crown of an American chestnut in
the open can spread a hundred feet. Longfellow must have been
inspired by one of these truly “spreading” giants. This was one
big tree, comparable to the redwoods in California. Like the
redwood, the American chestnut was prized as a source of
sturdy, rot-resistant lumber.

Those chestnuts roasting by the fire today are likely to be Asian
chestnuts because, like the whooping crane, the American
chestnut was brought to the brink of extinction. During the
twentieth century, over three billion American chestnuts died!
The culprit is chestnut blight, caused by a fungus known as
Cryphonectria parasitica (let’s call it CP for short). As with so
many problems today, West Nile and AIDS, for example, CP is
an alien species that was imported to our shores. In CP’s case, it
is thought to have stowed away in a shipment of Japanese
chestnut trees ordered by a Long Island nursery in the late 1800s.
Mail orders for cuttings from these trees spread CP from Maine
to Mississippi.

I learned of the plight of the American chestnut from the article
“Return of the King of the Trees” by Karen Wright in the May
issue of Discover magazine. The article deals in part with the
work of Gary Griffin, Professor of Forest Pathology at Virginia
Polytechnic Institute. For additional information, I visited the
Web site of The American Chestnut Cooperators’ Foundation
(ACCF), run by Lucille Griffin (Gary’s wife, daughter or
sister?). The ACCF is a nonprofit foundation “dedicated to
restoring the American chestnut in our Eastern hardwood
forests.” Comparing the task of bringing back the whooping
crane to that of bringing back the American chestnut, for
relatively quick gratification I would join the whooper people.

Cranes can breed more cranes in a few years but to see whether
you’ve been successful in combating the chestnut blight takes
decades. In fact, chances are that you won’t live long enough to
really know how successful you’ve been. Trees are not rapid
growers. A tree must be at least seven years old before it starts
making nuts and there’s no point to testing a tree for blight
resistance before it’s five years old. The blight causes rapid
growing deep cankers that kill tissue and cause the tree’s demise.
On a blight-resistant tree in a blight-infested area, cankers still
form but they are superficial and slow growing and the tree
survives. However, these slow growing cankers can change into
the fast growing destructive type; hence the problem that, many
years after you think you’ve been successful in beating the
blight, it may win out in the end.

So, how to beat the chestnut blight? The American chestnut
itself is trying to wage its own comeback. New shoots sprout
from stumps or old root systems of trees than have fallen to the
blight. Unfortunately, the CP doesn’t go away but sticks around
in the old roots and comes back to attack the new shoots.
Thankfully, there are the rare chestnuts that still stand, even in
heavily blight-infested areas. The ACCF is trying to bring back
the American chestnut by raising and distributing seedlings from
nuts taken from these seemingly blight-resistant trees. The hope,
of course, is that the offspring of these trees will also be blight-
resistant.

Researchers aren’t just hoping that propagation of blight-resistant
trees will do the trick. There is a virus that infects and goes after
the CP fungus. This “hypovirulence” is being used in the blight
fight. The approach is to inoculate the slow growing cankers on
blight-resistant trees with the hypovirulence. Back in 1980,
branches from three resistant trees were grafted onto sprout
clumps and in 1982 and 1983 the first cankers were inoculated
with hypovirulence. These grafts are thriving and have been
producing nuts for a decade, even though surrounded by non-
resistant trees that keep getting killed back by the blight. The
largest is now over 60 feet tall and 20 inches in diameter “at
breast height” with few branches killed by the blight.

The first approach to solving the blight problem was
crossbreeding, begun back in the early 1900s. In this approach,
man steps in to modify the normal pollination process. The
American chestnut has male and female flowers on each tree. A
tree can’t self-fertilize and the pollen from a male flower must be
transported, normally by wind and insects, to a female flower on
another tree. What the breeders do is to place bags over the
newly emerged female flowers of the “mother” tree, wait a week
or so and then fertilize the bagged flowers with pollen taken from
the male flowers of the “father” tree. They do this by misting the
female flower and either painting it with the pollen on a brush or
by dragging a cluster of male flowers across it.

By keeping careful track of the bagged flowers, the breeder can
cross the American chestnut with the more blight-resistant Asian
varieties or, the ACCF approach, with other blight-resistant
American chestnuts from various areas. The nuts harvested from
the bagged flowers can then be used to seed the new crossbreed
hybrid chestnut. As noted, crossbreeding of Asian and American
chestnuts began back in the early 1900s, when the extent of the
blight devastation was realized. While the crossbreeds may have
better blight-resistance, they are much smaller trees than the pure
American chestnut and have trouble competing in the forests
with other trees such as the maples, beeches, ashes and oaks.
Accordingly, “backcrossing” the hybrid Asian-American trees
with the most blight-resistant American chestnuts has been going
on. This approach tries to keep the blight-resistance genes of the
Asian chestnut in a hybrid having more of the characteristics of
the American variety.

The cross- and backcross-breeding to obtain all kinds of mixtures
of the traits of the Asian and American varieties takes
generations of trees to achieve. Hopefully, at least one of the
varied approaches will succeed and the country will once again
have billions (or at least millions) of these giant trees covering
the forests of the eastern United States. The Discover article has
a picture of an 88-foot-tall American chestnut in Olympic
Memorial Park in Tumwater, Washington. This is the largest
healthy American chestnut in the country, grown in the West, far
from the range of the blight in the eastern part of the country. To
really appreciate the size of these trees, take a look at another
picture taken circa 1920 in the article. It shows a man (seated)
and four women standing at the base of an American chestnut. I
measured the height of the women in the picture and, assuming
they were only 5 feet tall, I calculate the diameter of the tree at
seven and a half feet. That’s one humongous tree!

I’ve just looked up the full text of “The Village Blacksmith” on
americanpoem.com. It’s rather long and there’s no way that at
the age of three I would have known the whole thing by heart. I
suspect that all I knew were the lines I quoted and that my
mother had overstated my capabilities, as mothers are wont to
do. Happy Mother’s Day to all you mothers out there! And let’s
hope those “mother” American chestnut flowers produce
children that will live long, blight-free lives.

Allen F. Bortrum