PETERBOROUGH — On Friday's sunny morning, 10 eighth graders from the ConVal School District planted 90 chestnut saplings in the American Chestnut Foundation orchard on Otter Brook Farm.

For the past few years this orchard has been part of the foundation's efforts to breed blight-resistant American chestnut trees.

The morning of work on the farm was also a way for the students to thank the farm, which they use year-round for their science class.

The eighth graders are part of a group of about 80 students from both South Meadow School in Peterborough and Great Brook School in Antrim that participated in a yearlong science program at Otter Brook Farm run in collaboration with the farm and the Hancock-based Harris Center for Conservation Education.

“Today is all about them giving back to the farm,” said Laurel Swope, a Harris Center naturalist. “Most of the year they are collecting data, whether it is for water quality, forest surveys, or animal-tracking. The data's used for the farm's natural resource inventory, because most of the farm is protected under a conservation easement.”

The other 70 students were at different locations on the farm that day, some planting a garden, others clearing hiking trails.

“This orchard is a breeding orchard for the Vermont/New Hampshire chapter of the American Chestnut Foundation and it's hosted by Otter Brook,” said Kendra Gurney, New England Regional Coordinator for the American Chestnut Foundation. “Our goal is to restore the American chestnut. So our main tool for doing that is a breeding program aimed to develop a population of blight-resistant American chestnuts.”

Each state chapter seeks out wild-growing chestnut trees to cross-pollinate with a breed crossed with the blight-resistant Chinese chestnut.

“We're really just trying to borrow blight resistance from the Chinese chestnuts. Otherwise we want trees that look and act like our native trees,” Gurney said.

In its native range from Maine to Georgia, along the spine of the Appalachian Mountains, there once had been about four billion chestnut trees on 200 million acres.

“Then in the late 1800s on imported nursery stock from Asia, we brought chestnut blight accidentally into the U.S.,” Gurney said.

Over the next 50 years, the American chestnut was essentially wiped out.

Young saplings still grow since the blight does not affect the strong root system of the trees. However, the trees are not maturing to reproduce or provide nuts and participate in the ecosystem.

“We've pretty much lost them as a forest tree,” Gurney said.

Trees planted in the Peterborough orchard come from trees bred with American chestnut trees found in Mason, Washington, Merrimack and Canaan that matured enough to flower.

“So it's kind of our shot of incorporating local genetics into our breeding program,” Gurney said. “The trees that we find are not blight resistant, often times they are heavily blighted. … There are chestnuts out there. They just don't typically last very long. We are just looking for chestnuts that live long enough to flower.”

The orchard was started in 2009 and now has about 240 chestnut trees growing in it. Gurney said the foundation plans to plant another 100 saplings in the fall.

“These trees will grow for a while and eventually we'll pick the best candidates for the next generation of breeding,” Gurney said.

Before the blight, chestnut lumber was popular because it was lightweight and rot-resistant.

The nuts were also a food source, she said. “We've heard Nat King Cole singing about roasting chestnuts on the open fire. People did that. They tasted good.”

“Chestnut was widely used,” Gurney said. “All those benefits were lost.”

Friday morning, students moved quickly, planting and watering the trees and were soon weeding the orchard, mostly pulling up wild blueberry bushes sprouting around the saplings.

While many of the students groaned at the idea of weeding, 14-year-olds Ben Graves and Joshua O'Curran of South Meadow School said they were having a good time.

“Oh, heck yeah, we love it,” O'Curran said.

After the morning of work the students went to the Harris Center for a year-end celebration of their science program.

mpierce@newstote.com