UNITY, Maine — For one weekend in September, all roads lead to the usually quiet central Maine town of Unity as tens of thousands of farmers, organic foodies, border collie enthusiasts and others make their annual trek to the Common Ground Fair.

Among a myriad of activities, attendees will have the chance to learn about a heritage apple project that practically makes John Bunker’s mouth water when he talks about it. Bunker of Palermo is a board member of the Maine Organic Farmers and Gardeners’ Association, the organization that holds the 37th annual fair. On all three days — Sept. 20 through Sept. 22 — he will discuss the new orchard he and others are creating about a quarter mile away from the fairgrounds on a reclaimed former gravel pit.

“About 150 years ago, there were 15,000 to 20,000 named American apple varieties,” he said. “In Maine, there were hundreds of different varieties. What I have been doing, with the help of other people, is to track them down and save them.”

About 40 of the apple varieties already are growing at a small heritage orchard on MOFGA property at the site of the fair. Bunker has an additional 225 trees in a nursery that are awaiting to be planted at the new, larger orchard, with the first batch to be put in the ground in April. The new orchard will have room for between 500 and 700 different varieties of the apples that were historically grown in Maine.

Why so many varieties? The answer, he said, has to do with the unique nature of apple trees, which reproduce asexually. Every seed that grows into an apple tree creates an entirely new kind of apple. The apple varieties that caught on — like the popular McIntosh, for instance — have all been grown via graft.

“What’s the history behind every variety?” Bunker, who said he’s still on the hunt for old, gnarled and nearly-forgotten apple trees, asked. “Each one has its unique story. Why are they still here? Who’s trying to save them?”

If people can point him in the direction of Maine’s “old, broken-down apple trees,” he said that would be very valuable to save the heritage trees. Otherwise, they can learn about the project and also about the new space, which will be terraced in a way similar to farms on Vietnamese hillsides.

“These apple trees are going to be perched on these terraces,” Bunker said. “It’ll be spectacular.”

In addition to learning about heritage apples, enjoying bean-hole beans, contra-dancing outside and listening to lectures on subjects ranging from alpacas to vermicomposting, Common Ground fairgoers can learn much more about preserving food via fermentation. Sandor Katz is Friday’s keynote speaker and self-described “fermentation revivalist.” He will speak at 11 a.m. Friday, Sept. 20, and perform a cooking demonstration at 2 p.m. Saturday, Sept. 21.

Katz said that fermentation is on the rise because people want to “reclaim their food and have some connection to it.”

Some fairgoers are likely to meet Ted Quaday, MOFGA’s new executive director, who will officially start on Oct. 1. Quaday of Santa Cruz, Calif. is an organic food advocate and former program director at Farm Aid. He succeeds Russell Libby, who led the organization from 1995 until his death late last year of cancer.

Bunker said that he and many others in the organization are excited to have Quaday start his new post.

“Russell Libby was one of my closest friends,” Bunker said. “I was very, very sad to see him go. The rest of us need to move on, and share his legacy.”

For more information about the Common Ground Fair, please visit the website www.mofga.org.

BDN writer Kathleen Pierce contributed to this report.