Frank Knight sat in a rocking chair on his back porch and pondered his feelings for Herbie.

For more than 50 years, Knight took care of Herbie, a 110-foot-tall American elm tree on Route 88 that is officially the largest elm in New England.

He saw Herbie through 15 bouts with Dutch elm disease, spraying, pruning, picking off bugs, doing whatever he could to keep the massive tree alive.

As a man who has worked with trees his entire life, Knight knows that Herbie’s current case of Dutch elm is fatal, and that the tree will have to be taken down this winter. It’s the right thing to do, but not an easy thing to do.

“Of course I’m sad, but everything’s got to go, ” said Knight, who is 100 years old and was Yarmouth’s tree warden for 50 years. ”It’s pretty near my time, too. I’m just glad we had Herbie all these years.”

Knight and the town’s current tree warden, Debra Hopkins, concluded this summer that Herbie would have to come down. They have begun spreading the word so that people can visit Herbie one more time, maybe have their children’s pictures taken with it.

No firm date has been set, but Herbie will probably be cut down in early 2010, Hopkins said.

The Dutch elm disease has essentially caused the tree’s system of carrying nutrients to shut down, said Hopkins.

An examination of Herbie’s core last month by William Ostrofsky, a Maine Forest Service pathologist, showed ”no indication of internal decay.” His report said there should be ”at least some substantial amount of usable wood in the stem.”

A committee of residents has been formed to decide what might be done with that wood. Ideas being tossed around include Christmas ornaments or pens for Yarmouth residents, or some sort of fine woodwork.

Taking Herbie down will probably cost about $6,000, Hopkins said, and it may cost another $12,000 or more to mill and dry the tree’s wood for use.

”I think it would be wonderful for people to be able to have a piece of Herbie, ” said Barbara Parkhurst, a member of the committee and a 36-year resident of the town. ”I think people who lived here awhile will definitely miss Herbie.”

There will probably be people beyond Yarmouth who will want a piece of Herbie. After all, it holds the Maine and New England titles as the largest standing American elm, said Jan Santerre, coordinator of the Maine Register of Big Trees for the state’s Department of Conservation.

The story of Herbie, and how Knight has worked to keep the tree alive all these years, has been written up in national and local publications.

Sitting on his porch Friday, Knight held a letter he got in 2003, addressed to ”Herbie the Champion Elm.” It was from the owner of the largest elm in Texas, and Knight proudly noted that the Texas tree was not as big as Herbie.

Over the years, people have written to Knight to ask for seeds from Herbie. Others have sent Knight checks to contribute to Herbie’s care and well-being.

The tree, estimated to be more than 230 years old, is at the corner of East Main Street – Route 88 – and Yankee Drive. It is partially on town land and partially on the front yard of a house owned by Donna and Irving Felker. The Felkers have agreed with Knight and Hopkins that the tree must come down.

Donna Felker, 67, grew up in the house closest to Herbie and gave the tree its friendly name, Knight said. She doesn’t exactly remember that, but she doesn’t dispute it, either.

Irving Felker said tour groups and individuals can regularly be seen on the sidewalk in front of Herbie, gawking at a trunk that is 20 feet around and limbs shooting up toward the clouds.

When he was a little more mobile, Knight could be seen there, too, on most days.

”The man is 100, but until four or five years ago I don’t think a day went by that he didn’t visit that tree, ” said Irving Felker.

Knight was still playing golf and splitting his own firewood when he was in his early 90s. Now he uses a walker to get around, so he has given the day-to-day tree warden responsibilities to Hopkins.

Knight began as tree warden when a rash of Dutch elm disease was breaking out in 1956. A couple of years later, he and others in town had to cut down 100 elms that had the disease.

Most of the time, diseased elms had to come down to save the trees around them, he said. Herbie was an exception.

Knight worked year after year to keep it alive. Besides strategic prunings, it got inoculations of a fungicide, every three years at first, then every year.

”It’s been cut about 13 times because of disease, but it was such a beautiful tree, ” said Knight. ”There were some bigger, but none more beautiful, with that nice straight trunk.”

Knight thinks it’s funny that stories about him and Herbie make him look like ”the biggest tree lover.”

Having been a pulpwood dealer and a woodlot owner, Knight said, he probably ”has taken down more trees than anyone in Maine.”

But there’s at least one tree that he won’t watch come down. He doesn’t plan to be on hand for Herbie’s last day.

”No, ” he said, ”I don’t need to see that.”