In late April, a spate of wind storms rushed through D.C., and a tree fell in Rock Creek Park. I wasn’t there to hear it, but for months after, I drove by, gloomily expecting to see a dying tree.
Instead, the tree continued to grow.
The storm uprooted the tree, laying it to rest across a roadside lawn on the eastern edge of the park. It was a white oak with a broccoli-shaped canopy and leaves with lobes like fingers. Weeks passed and I drove by occasionally, glancing out the window, checking its vitals. The fallen oak bloomed white with its neighbors in late spring and turned its wide leaves to the sun.
In August, it was removed from the lawn where it made its summer home. But until then, despite everything, the tree was alive.
The white oak spent its life on a low, anonymous hill at the intersection of Piney Branch Parkway NW and 17th St. NW. Neither park nor city, the intersection is one for venturing deeper into the park, getting from one neighborhood to the next, or going to Virginia, by way of Theodore Roosevelt Bridge. One would not visit this particular crossing without intentions to immediately depart. Before it fell, the white oak wouldn’t have attracted much attention either. After seeing it fall and live to tell the tale, I wanted to know: Was this particular tree special at all?
Urban foresters know the plight of fallen trees has as much to do with a tree’s underground bits as it does the above. Usually, even a fierce storm isn’t solely responsible for a tree’s collapse. For each downed tree, countless others weather the storm. Storms just tend to be good at finding the most vulnerable trees.
When I asked Doug Rowley, Rock Creek Park’s head horticulturist, about the fallen tree, he immediately knew the one. It wasn’t a tree that would have stood out as a hazard, he said. Rowley wasn’t certain of its age, but estimated it was 35 to 45 feet tall and 27 inches across, almost as wide as a folding table. When it fell, the oak stretched deep into the lawn on the side of the road, towards cars and joggers.
“It’s what they call a windthrown tree,” he said. “The trunk goes over, and the whole root system is uprooted on one side.”
Roots and all, oaks are shaped like a wine glass — if the foot stretched out two times the width of the cup. Roots burrow into the earth, foraging for oxygen, water, and nutrients. Often, a central taproot sinks down, but most of the roots won’t grow deeper than oxygen in the soil. Since that tends not to be more than a foot belowground, oaks are vulnerable to damage from bustling activity overhead, like trail running, lawn-mowing, or construction work.
Windthrow can snap a tree’s roots clean through, or, in the white oak’s case, lift the entire root plate — the foot of the wine glass — into the air. Previous root injuries weaken a tree’s foundations, making it more susceptible to rough winds. Wounds open the door to pests and disease. In a survey of 80 mature, windthrown trees over two decades, University of Melbourne urban forestry scientist Greg Moore reported nearly 90% had experienced prior root damage.
This particular oak spent its life on a gravelly hillside at the edge of a wooded area. Rowley recalled D.C. was getting more rain than usual leading up to the fall. Waterlogged soil stresses trees, choking roots so they can’t take in oxygen. And, maybe after all the rain that April, Rowley suggested, the slick, wet soil couldn’t hold the heavy roots any longer.
Upon his survey of the windthrown Melbourne trees, Moore reported more than half suffered from too much rainwater. In the Washington region, climate change is expected to bring wetter, wilder storms — and with that, floods. Increasingly, arborists will need to consider trees’ personal history, including previous bouts of flooding, when they assess trees for risk of windthrow. Besides poor canopy health, signs of damaged roots and evidence of compacted or waterlogged soil indicate increased likelihood of falling.
Apart from falling in the first place, the white oak was a lucky one: The spill left its roots and leaves mostly unscathed. Since its roots weren’t oriented in the direction of the fall, they erupted from the soil in one piece.
“About half the root system was still intact with the ground,” Rowley said. “There was some cracking — a little less than half — but there was enough there to supply the water needs of the tree.” Also, by the time it fell, the tree had donned its summer leaves. Even on the ground, they kept photosynthesizing. Life goes on, horizontally.
After the storm, someone filed a removal request with DC 311, the city services department. The request bounced to the Urban Forestry Division, which determined the oak fell within the boundaries of Rock Creek Park — National Park Service property. They handed the request over to the Park Service. Since the fallen tree wasn’t obscuring any walkways and presented no immediate hazards, they marked it a low-priority case. The oak kept growing.
In late August, a Park Service crew finally made their way to the tree. Had they not gone, Rowley says, it would have eventually succumbed to late summer heat; the exposed roots couldn’t have pulled enough water for much longer.
Branch by branch, the crew pared the tree down until it resembled a telephone pole. They chopped the trunk into manageable pieces and hauled them away. Later, they’ll grind the logs into woodchips, which they’ll process into mulch.
“Next spring, we’ll use the mulch in our flower beds in different areas around the park,” Rowley said. “We try to recycle what we have to take.” The oak should produce enough mulch to fill a small pick-up truck.
In early November, I visited the intersection again, parking for the first time. Ivy grew over the site of the fall, dulling the feel of upheaval. The crew removed almost the entire tree, but splaying root flares and around five feet of the trunk remain.
“Where we can, we leave what we call snags,” Rowley told me before. “That provides habitat for birds and squirrels over time as the stump decays.”
Already, the soft wood showed signs of decomposing. Frilly lichens slowly dined. Scattered woodchips, coughed up from the chainsaws, melted into wet leaves on the ground. In the spring, the soft oak mulch will blanket flower beds, sheltering fresh growth, and the snag will meet its new neighbors. The white oak will find new ways to grow. I turned to leave and startled a squirrel hunting for acorns.
