Butternut trees are threatened by a fungal disease that eventually kills them. It can be hard to find one that’s not already affected – which is why ecologists at the Pittsburgh Parks Conservancy were so excited by a recent discovery in Frick Park.
The forest behind the Frick Environmental Center is lush. But walk about 500 feet along the Clayton Hill trail and you come to a clearing, a break in the forest canopy.
“It looks a little bit shocking when you first see it,” says Judith Koch, volunteer landscape coordinator for the Pittsburgh Parks Conservancy.
A Wall of Honeysuckle
Over the winter, Koch worked on a restoration project in this area. A giant stand of invasive bush honeysuckle – about 2.6 acres – had taken over making the area impassable. It needed to come down before it smothered whatever was growing below.
“This whole area, you couldn’t see anything,” Kochsays. “It was just a wall of bush honeysuckle. You could not walk in here. It was so crazy.”
The honeysuckle in this patch of forest likely escaped from someone’s yard and had been growing, unchecked, for about two decades. And once it was cleared, the parks staff made an important discovery: Ten strong, full-grown butternut trees. This news was thrilling to Conservancy staff because a healthy butternut is a very rare find.
According to the Pittsburgh Parks Conservancy, every butternut in Frick Park – except for these newly discovered ones – shows symptoms of a disease called butternut canker. Canker is caused by an exotic fungus that spreads easily through a forest. When a butternut gets canker, it develops an oblong-shaped abscess that oozes. The wounds eventually cut off the tree’s nutrient and water supply, and it dies. In some states, 80% of the butternuts have been killed by it.
“To us it’s pretty exciting, because it is so sad to see to us lose tree species,” says Koch. “There are just so many threats to our native trees that seeing trees that are not diseased, that are withstanding something that is spreading throughout the country and taking out entire species — that is a big deal to us,” says Koch.
Butternuts are a widespread but now rare hardwood native to eastern North America. Also known as white walnuts, they used to be abundant in Pennsylvania’s forests. Their nuts — an important food source for squirrels and other wildlife — were collected and eaten by indigenous people in this region.
LISTEN: “Restoration Work Leads to Big Surprise in Frick Park”
The Pittsburgh Parks Conservancy staff doesn’t know exactly why these butternuts don’t have canker. They will be closely monitoring them for the next couple years for any signs of the fungus. If they remain canker-free, the conservancy staff will collect their DNA and add it to a genetic database of the city’s strongest trees. And they’ll also use the seeds to grow new trees that will be used to re-populate this site.
“That is one of the greatest things about Pittsburgh, that we are so green, and we have so many parks. So it’s really important to preserve them and make them stronger.”
“We want to see if they are maybe not susceptible to the canker or just a little bit stronger than other butternuts,” explains Koch.
Lots and Lots of Weeding
For now, the hard work of forest restoration continues. That means trying to keep the area free of invasive species like that pesky honeysuckle that is already creeping back. And because no pesticides are allowed in city parks, that means lots of old-fashioned hand weeding. Kochhas spent hundreds of hours out in Frick Park weeding with volunteers.
On this day, Koch has a chainsaw to help. And also three interns. But she hopes to find funding to bring goats to the site soon.
“They’re just very efficient at munching down any invasive plants that are sprouting,” she says. “Much faster than me and the interns.”
Ideally, the Pittsburgh Parks Conservancy says they will begin planting restoration trees on the site in two to three years. And in another 10 years, they are hopeful that the tree canopy will be closed by healthy canker-free butternut trees. It’s a commitment and a lot of work, Koch says, but worth it.
“That is one of the greatest things about Pittsburgh, that we are so green, and we have so many parks,” says Koch. “So it’s really important to preserve them and make them stronger.”
The Parks Conservancy is always looking for volunteers to help with restoration projects in Pittsburgh parks. There’s more information here.