Bruce Levine, with the American Chestnut Foundation, looks for a ripe chestnut at an orchard of hybrid trees.
The American chestnut tree was once called "the redwood of the East" because of how huge it could grow. It was an amazing food source: each fall, the tree would drop an unbelievable bounty of tasty and nutritious nuts — feeding wildlife, livestock and people. The tree was wiped out a century ago by blight, but the American chestnut can still be found clinging to life in forests around D.C. and across the eastern U.S. It could make a comeback, thanks to modern science and a highly committed cadre of chestnut aficionados, including dozens of locals who volunteer their time and land in an attempt to bring the tree back from the brink of extinction.
American chestnuts were once among the most common trees in forests in the D.C. area, accounting for as many as one in four trees in some places. Nowadays, finding surviving chestnuts isn't easy — but a few hundred have been documented growing wild recently in the District, Maryland and Virginia.
In Rock Creek Park, a handful of American chestnuts can be found on the steep eastern ridge above the creek.
Leaves of an American chestnut growing in Rock Creek Park near Carter Barron Amphitheatre.
"This is a tree, I'm sure thousands of people have passed and never paid any attention to," says Gabriel Popkin, pausing at one of the chestnut trees. Popkin is a local science and environmental writer who leads occasional tree walks.
The tree he's stopped at is a completely unremarkable sapling, blending in with nearby beech and chestnut oaks, which have similar leaves. The chestnut is identifiable by its sharply saw-toothed leaves (beeches have much shallower serrations, while chestnut oaks have rounded serrations.)
This small tree is what is known as a stump sprout — a young tree growing from old roots.
"That's the tree trying to make another go at it," says Popkin.
When chestnut blight attacks, it girdles the tree's trunk, cutting off nutrients and killing everything above. But the roots can live on, repeatedly sending up new sprouts, only to have them knocked down after a few years. Nowadays, the "redwood of the East" very rarely grows large enough to flower and bear fruit.
'The Wail Of The Chestnut Tree Lover'
The story of the American chestnut's demise starts in 1904, at the Bronx Zoo in New York City. The zoo's forester found small orange-red dots on the bark of chestnut trees, and cankers encircling the trunks. Affected trees succumbed quickly.
By 1908, blight had made its way to the D.C. area, with reports coming in from Maryland and Virginia.
"All the chestnut trees in the United States are doomed to destruction," wrote the New York Times, as efforts to contain the blight were stymied. In just a few years, the chestnut blight had killed thousands of the valuable timber trees, an economic loss of $5 to $10 million. It was the "most rapid and destructive" fungus known to the world, according to the Times.
A chestnut trunk bulging with blight at the TACF orchard in Montgomery County.
"The wail of the chestnut tree lover is heard from all parts of New York, Long Island and adjacent country," wrote the Times in another 1908 story, oozing with helplessness and distress. Experts at the New York Botanical Garden had received hundreds of letters, "containing almost piteous appeals for help from people whose trees were dying."
The pathogen had traveled over the oceans on shipments of imported Japanese chestnut trees. The Asian trees were blight resistant, but the fungus spread unchecked among the defenseless American trees. People tried all sorts of things to stop the spread: spraying with various chemicals that had worked on other pests, even cutting down mile-wide swaths of trees as a sort of firebreak against the fungus.
"Pretty quickly people realized there was just nothing to be done," says Popkin. "It was just this scene of total devastation."
By around 1950, an estimated 4 billion American chestnuts had been killed by the fungal blight.
But there are still likely millions of American chestnuts, sprouting from old roots, struggling for survival in forests throughout the D.C. region (and elsewhere in the eastern United States). The National Park Service documented living chestnuts in D.C.-area parks in a 2014 inventory.
A tagged chestnut in Rock Creek Park.
"We found a surprising number," says NPS ecologist Liz Matthews, who worked on the project.
In Rock Creek Park, 20 trees were found. There were 27 along the George Washington Memorial Parkway, and 29 at Wolftrap. Catoctin Mountain Park, in Maryland, had the most trees: 98, including 4 that were flowering. One large tree was discovered, 78 ft. high, tall enough to reach the forest canopy.
But most trees were small, with an average trunk diameter of about 3 inches.
Matthews says the easiest way to find American chestnut sprouts is to look for co-occurring species. The presence of mountain laurel, in particular, is a good indicator chestnuts may be growing nearby. Another way to find chestnuts (and report them when you do), is with the citizen science app iNaturalist, which currently has dozens of reports of chestnuts in the region.
"Once you start looking, you can't stop finding them," says Matthews. "We had interns working with us that summer we did the inventory and they got hooked."
Ecologist Liz Matthews in Rock Creek Park.
'Nature Has Solved The Problem'
Bruce Levine, of Takoma Park, Md., also got hooked on chestnut trees after stumbling upon a few in the wild, about 25 years ago.
"I thought I had found the only chestnuts left," recalls Levine. He knew blight had wiped out the American chestnut, and didn't realize there were still survivors. "I went home and started Googling — I don't know if they had Google — I started Yahooing or something."
In his Yahooing, he came across the American Chestnut Foundation, which has been working to create a blight-resistant American chestnut tree for decades. Levine is now president of the Maryland chapter.
At a chestnut orchard operated by the group in Montgomery County, Levine shows off some of the progress. Most of the trees in the orchard near Sugarloaf Mountain are hybrids — a cross between American and Chinese chestnut trees — and are at least somewhat blight-resistant.
Levine points out his favorite tree — it's growing tall and straight like an American chestnut, but shows signs of good blight resistance. It's being attacked by the fungus, but it's fighting back.
"You see that it has these chestnut blight cankers on it, including a big one up at the top, but it's kind of superficial," says Levine, examining the tree's bulging bark.
Bruce Levine examines a blight canker.
Chinese trees have developed resistance to blight over millennia. Now TACF is attempting to transfer that trait into trees that are mostly American through a breeding program.
Breeding trees is not easy work. For one thing, it takes years before they're old enough to reproduce.
"This is not like corn where you get one or two crops a year," says Levine. "It's like 10 years a generation."
The orchards require lots of land, most of it donated, and volunteers to tend the trees. In Maryland alone, the foundation has more than 10,000 hybrid chestnut trees growing in 22 orchards, cared for by dozens of local volunteers tree-lovers. In Virginia, the foundation has another 14 orchards.
The trick is to create a hybrid tree with the tall growth habit of an American tree, so it can compete with the towering oaks, tulip trees and maples that now dominate eastern deciduous forests, but that also has the blight resistance of the lower-growing Chinese tree.
To do this, TACF begins with one American parent and one Chinese parent, creating offspring that are a 50-50 hybrid. Volunteers then "backcross" those hybrids, breeding them with pure American chestnuts, and only retain the most blight-resistant trees. This backcrossing is repeated for three generations, resulting in trees that are more than 90% American.
The TACF orchard has many open spaces with stumps of trees that were not sufficiently blight-resistant.
But Levine says blight resistance is turning out to be more complicated than originally thought, involving more genes. Starting this year, TACF is changing its procedures to try to speed up the process, weeding out weak trees earlier and only crossing the best parents with each other.
Levine is still optimistic about the breeding program. "It's a slow process, but it definitely will eventually work," he says. "Nature has solved the problem of chestnut blight."
It's just a matter of transferring nature's solution into American trees.
The First Transgenic Trees
Meanwhile — there's another, parallel effort to bring back the chestnut. Scientists at the State University of New York College of Environmental Science and Forestry in Syracuse successfully used genetic engineering to introduce a blight resistant gene from wheat into the tree. Journalist Gabriel Popkin has written about the project; he says it's a first for genetic engineering.
"This idea of using it to reintroduce a native tree, and really for noncommercial purposes — yeah, that's totally new. It sort of takes the GMO controversy and puts a whole new spin on it."
Bringing back a species that was wiped out before most people in this country were born may sound a bit like Jurassic Park. Genetically modified organisms are controversial, and some chestnut enthusiasts are opposed to GMO trees. But Popkin says it's hard to imagine the slow-growing chestnut turning into an unstoppable superweed.
The TACF orchard has many open spaces with stumps of trees that were not sufficiently blight-resistant.
"If the American chestnut started reproducing out of control, most people would probably think that's a good thing. It's a great tree," he says. "I thought about it for a while, and it was hard to really get myself feeling too anxious about it."
The transgenic tree is currently under review by the U.S. department of agriculture. Even if it wins approval there, there are numerous other agencies that would have to sign off before GMO trees could be introduced.
Aside from that, reintroducing the American chestnut comes with a host of other challenges — whether it's a GMO tree, or one created through the TACF breeding program.
NPS ecologist Liz Matthews says one issue is that other trees have taken the place of the chestnut in the woods around D.C.
"These forests are not the same forests that occurred in 1940, when the chestnut declined," Matthews says. "All sorts of things have happened: climate change; the forest has undergone succession — so a different group of species. It would be a real challenge, I think, to reintroduce the American chestnut."
Still, the prospect of eventually bringing back the iconic tree offers a glimmer of hope on a warming planet beset by species extinctions. Some day, forest floors in D.C., Maryland and Virginia could again be blanketed by spiky chestnut burrs, feeding squirrels and raccoons and human foragers.
This story is from DCist.com, the local news website of WAMU.