Of all the trees along the Milford Upper Charles Trail, one made Michelle Clay stop and take a second look.

The 30-foot tree, right next to the walking trail, was an American chestnut. And it was flowering.

"My jaw dropped," said Clay, a resident of Franklin. "I'd never seen one in bloom before."

The American chestnut — a giant once known as the Sequoia of the East — is a fast-growing, hardwood tree that was wiped out by a blight by the 1930s. What remains in the landscape, including the tree along the Milford trail, have sprouted from the roots of those old trees.

The blight, which still remains active, typically kills them off by the time they mature enough to bloom. That's what makes the Milford tree unusual.

Clay contacted the American Chestnut Foundation, a Asheville, NC-based foundation trying to resurrect the tree by creating and planting blight-resistant hybrids.

A group of foundation volunteers, from the Massachusetts chapter, got town permission to place small bags around the flowering ends of the tree that were within reach. Each bag contains pollen from a hybrid American chestnut — an American chestnut pollinated by a Chinese or Japanese chestnut that is blight-resistant, said Kendra Gurney, New England Regional Science Coordinator for the Chestnut Foundation.

The hope is to collect the chestnuts that eventually form, and plant them in a Chestnut Foundation orchard. As they grow, these saplings would continue to be paired with American chestnuts, and eventually reintroduced to forests, Gurney said. Over time, if the effort is successful, the reintroduced trees will have blight reisistance, but have almost all of the features of the old American chestnut.

About 20 trees across New England are now in a pollination phase, she said, including the tree in Milford. "It's pretty rare," she said, of finding a flowering specimen.

What makes the American chestnut worth such effort? The tree once dominated Eastern forests. It was massive when mature, Gurney said, and the trunks often had a three- to five-foot diameter. (measured at a man's chest level)

It was a very good timber species, she said, rot-resistant. And its nuts were prized by wildlife and people alike. For that reason, she said, once the squirrels figure out the chestnut in Milford is forming nuts, she said, the Chestnut Foundation will have to guard the contents of the little bags.

"Once they know what's in those bags, it's a race for time," she said.

Clay, who wrote in her gardening blog about her experience in spotting the American chestnut, likened the discovery to seeing a unicorn.

"I never thought I would see an American chestnut blooming in the wild, much less find one myself," she wrote.