THAT I SHALL NEVER SEE A POEM lovely as a tree . . .
As an elementary
school student, Don Smith, self- proclaimed lover of trees, won
a blue ribbon for reciting this Joyce Kilmer poem.
up in West Texas without many trees. I don’t take them for granted,”
says the UNT associate professor of biological sciences.
is helping to save the post oak — the Dallas-Fort Worth area’s predominant
native tree —from death by insufficient water absorption.
root of the problem
oak, or Quercus stellata, thrives in warm climates from Texas to
Georgia. Post oaks may grow up to 50 feet tall and 2 feet wide and
may live 100 years or more.
of these rugged trees are hypersensitive, reacting to any root system
disturbance by slowing down production of root hairs.
extensions of epidermal cells are located on new roots smaller than
a little finger. Root hairs live less than a month but absorb more
than 95 percent of a tree’s water and minerals, Smith says.
roots are not necessarily more absorptive than larger roots, but
they make up a large fraction of the total surface area available
for absorption,” he says. “Very little absorption occurs in roots
much more than an inch from the growing tip, so a tree must constantly
produce new root hairs to thrive.”
he first became aware of post oaks’ hypersensitivity a decade ago
through his tree-trimming business.
that many trees located in new construction sites died within a
few years. It was obvious that insufficient water reached the tips
of limbs. People asked me why this happened, and I got tired of
answering, ‘I don’t know,’” he says. “I decided to find an answer.”
out irrigation system problems, Smith tried to discover if a parasite
was destroying the trees’ roots. But the roots, even in dying trees,
appeared healthy. He soon discovered that any disturbance to most
post oaks’ root areas, such as a bulldozer driving across nearby
ground or a new sidewalk being paved, resulted in slowed growth
of new root hairs because of decreased production of new roots.
groan and say post oaks ‘don’t do well with civilization,’ which
is accurate,” Smith says.
species of tree becomes somewhat distressed in construction areas,
but most begin to thrive again soon after construction ceases, Smith
says. However, approximately 80 percent of post oaks in construction
sites die if their root growth is not stimulated, he adds. Smith
says builders preserve these trees to provide highly desired shade
homebuilders pay thousands of extra dollars for lots with large,
50- to 100- year-old trees,” he says.
are impossible to replace in a lifetime, he adds.
see them in nurseries because they usually can’t be transplanted
without dying,” he says. “You cannot replace post oaks unless you
start with an acorn. Sadly, while trying to preserve and take advantage
of the beauty and utility of these lovely trees, we are killing
significant numbers each year.”
signs point to a declining post oak, including thinning leaves.
When a tree is in full foliage, “you should be able to stand under
it, look up and not see any sky,” Smith says.
of water sprouts — twigs that grow out of the bark of a larger limb
rather than from a joint on another twig — and less than 6 inches
of annual growth on the tree’s twigs also indicate that a tree is
root growth in ailing post oaks through a homemade treatment.
Although early spring is the ideal time for fertilizing,
Smith says it’s more important to fertilize healthy post oaks before,
or soon after, nearby construction starts to ward off future slowdown
of root growth. Unhealthy post oaks should be treated as soon as
possible.“I actually get more calls during the summer because it’s
then that people notice thinning leaves,” he says.
the treatment, Smith has fertilized approximately 200 trees, including
post oaks adjacent to the construction site for UNT’s new Gateway
Center. He has an 80 percent success rate for saving trees.
tree dies despite my treatment, its energy reserves may have been
too low to grow more roots, and the treatment, by stimulating production
of new roots, hastened death by exhausting the meager food supply,”
Smith says. He adds that when he has applied the treatment before
or soon after the root area is disturbed, the trees almost never
go into decline. Smith says he hopes his research will ultimately
result in post oaks existing and thriving despite new construction.
easy to maintain, and they’re part of our culture. You see many
references to the strength of oaks in literature,” he says. “We
should do everything possible to preserve them.”