Recently, I was looking for homeowners willing to have trees planted in the right-of-way on their properties. A neighbor said, “What I’d like to see is walnuts. If you could find me walnut trees, I’d take as many as you’d give me.” This made me think about local street names and the characteristics of the trees whose names they bear.
Walnut. Even though my neighbor asked for walnut trees, as a shade tree commissioner, I would not be able to approve his request. For use as street trees, walnuts are a bad choice. The first obvious problem is the walnuts themselves. By mid-September, the ground under walnut trees begins to get covered with the lemon-looking, brown-staining flesh that surrounds the walnut. I don’t think you would sleep through the night hearing this hailstorm attacking the car parked on the street in front of your house, and I don’t think you would go to sleep at night thinking about the possibility of the lawsuits when pedestrians walking down your sidewalk take an unwanted weeks’ long detour into the hospital.
The second problem with walnuts is their roots. Remember survival of the fittest? Well, walnuts cheat at life’s most basic game: Instead of facing their plant competition in a head-to-head battle, walnut roots secrete a chemical called juglone into the soil. Juglone prevents many plants from growing near a walnut tree. So if you plant a walnut in a streetscape, the walnut might be the only plant in the streetscape.
Poplar. When I think of poplar, I think of a customer we had several years ago. A larger-than-life character, his discretion in choosing plants was no better than his love for his neighbor. So likely he was a fine target for the sales pitch I have seen in some plant catalogues: “Poplar variety grows 8 to 10 feet in a year!” Planted in a row along the back of his small property, soon the poplars towered over his house, and soon his lawn was covered in roots and suckers. Once the weak wood started breaking, he paid a steep price to remove the dozen trees and their roots and re-landscape. These poplars would be a terrible choice for street trees.
A better choice, but not a true poplar, would be the tulip poplar. But this towering native tree is better suited for parks than streets.
Ash. Get out your handkerchief: The temporary end of all American ash trees is near, thanks to the emerald ash borer (EAB). As recently as this decade, the ash was a common, large canopy street tree. But alas, like the elm and the chestnut, we will probably have to wait most of a lifetime until its replacement emerges from a university lab.
Linden. Let’s listen to the bees and plant more. Beside air pollution: “trouble-free.”
Reach me at email@example.com.
Joshua Arp is an ISA-certified municipal specialist, Clarks Summit’s municipal arborist and an operator of an organic lawn and landscape maintenance business.