Dutch elm disease leaves lone survivor on Pentacrest

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Thursday, March 1, 2012

It stands like the last of a people, the only survivor of a plague that all but wiped out a population with only a few stragglers in its wake.

Once, more than 100 American elm trees graced the Pentacrest, creating a towering canopy that shaded generations of University of Iowa students and faculty and provided homes to who knows how many birds and squirrels and whatever other animals lived in its limbs.

But then Dutch elm disease moved through and claimed all but this one that stands in front of Schaeffer Hall, still glorious despite the obvious ravages of time and wind storms.*

* More than 2,000 American elms once grew across the UI campus, but only two survived the Dutch elm plague. The other is near Reinow Hall and is much younger, smaller, and generally less inspirational than the one on the Pentacrest.

Andy Dahl, the university’s arborist, says no one is sure how old the tree is. Based on photos, he estimates it was planted sometime in the 1880s. The trunk is about 15 feet around and the highest branches grow to about 93 feet, high enough to loom above the three-story Schaeffer Hall. The tree’s root network could extend out as far as 50 yards from the trunk, though it reaches down only about 18 inches below the ground, not as impressively deep as an oak. It is, in fact, a state champion, certified as the largest American elm in Iowa.*

* Its giant cousin on the Pentacrest, the walnut tree growing in front of Macbride Hall, is also a state champion.

For years, it was about as elm an elm as you can get, with a full, high crown and a wide canopy, “that classic elm shape,” Dahl says, until a 1998 windstorm tore off the top 20 feet of its highest and longest limbs. It was the kind of tree to inspire poets to pick up their pens, artists their canvases, and Frisbee-throwers their Wham-Os. What is it that makes a tree so inspiring, to artists and non-artists alike? David Hamilton, professor of English, thinks it’s in our DNA.

“They’re older than we are, and they’re bigger and stronger,” he says. “We lived in the jungle before we moved into the savannah so they’re our ancient home. We climbed up into them to escape predators.”

Humans like big things, he said.* We are awed by skyscrapers and aircraft carriers, dinosaurs, whales, and elephants. It’s not an accident that one of the university’s icons is Rusty, the giant sloth. Trees are the whales of the plant kingdom.

* Unless it’s a bug. Giant bugs we don’t like much.

Literature is filled with paeans to trees, from Shakespeare’s plays to Kilmer’s poem to Dr. Seuss’ The Lorax. Hamilton imagines that early on, people saw as much fear as beauty in trees. Trees meant wilderness, darkness, and mystery, a place for highwaymen and wolves.

But over time, as the wilderness was tamed as farmland or urban space, trees became symbols of grandeur and beauty, something that could bring a person peace in an increasingly hectic world. In plays like As You Like It and A Midsummer Night’s Dream,for instance, Hamilton says Shakespeare used the forest as a place of restoration, where his messed-up characters could straighten out their lives.

“At some point in our history, the outdoors go from being fearsome and dangerous to offering an improving adventure,” he says. “Shakespeare may be more than a little responsible for our national parks and wilderness preserves.”

That love of trees has only accelerated in recent decades, as our understanding of the environment makes the loss of a tree not just a lost link to the past but a potential threat to our future. W.S Merwin’s poem, “Unchopping a Tree,” touches on that sense of tragedy. (Read more: observatory.designobserver.com/entry.html?entry=7857)

“Every time one goes, we’re more aware of what we’re losing,” Hamilton says.

It was not humans but a plague that wiped out the Pentacrest’s elm population, and how the tree managed to survive is a mystery, Dahl says. Dutch elm disease is carried by a beetle that arrived in North America in the 1920s, made its way to the Midwest in the 1950s, and destroyed millions of trees through the 1960s and ’70s, including those on the UI campus. Look at old photos and the Pentacrest seems almost like a rain forest with all the elms. But Dahl says that such a great concentration of a single species of tree in such a confined space helped to doom the elms, as it left the entire forest vulnerable to attack.

“It was too much of a good thing,” he says. “We created a plant monoculture and because there was so little diversity, when plagues came through, all the trees of that species got sick.” Had there been fewer elms on the Pentacrest and more oak or maple, he says the devastation would have been less severe.

It’s possible another blight will soon cause the mass deaths of more trees on campus, as the emerald ash borer moves west and leaves huge swaths of dead ash trees behind. The campus is home to somewhere between 700 and 800 ash trees—most notably, those lining Cleary Walkway—and Dahl says they’re all in danger.

The Pentacrest elm’s survival could provide clues as to how to save the ash, but Dahl says the best lesson the elm provides is that it’s good to be lucky. Dutch Elm was a fickle killer, wiping out most American elms but sparing others. One grove would be attacked and killed, but a grove a block away was left untouched. How this elm has survived, no one is sure.*

* Just to make sure it survives, it receives periodic injections of the fungicide Propiconazole to protect it against the occasional resurgence of Dutch elm disease.

Besides, he says, trying to save hundreds of ash trees would require resources beyond what the university can muster. He says Facilities Management will try to save a handful of strategically placed ash, but others will have to fend for themselves.

But ash trees, while lovely to look at in their own way, don’t grow to the height or the fullness of an American elm,* so future generations will likely not mourn the loss of ash trees as we still mourn the loss of the elms. Dahl says a typical elm’s natural lifespan is about 250 years, which means the Pentacrest elm has about 120 years left to awe and inspire if it can avoid future beetle infestations or nasty windstorms. That’s several generations of artists and poets and shade-seekers and Frisbee-tossers.

*They also litter the yard with lots of twigs and sticks and seed pods so they’re kind of a pain to clean up after.

“I hope it outlasts my tenure,” says Dahl, who admits the elm is his favorite tree on campus. “I don’t want to be the one who has to take it down. That would be a sad day.”