More than a century ago, J. Sterling Morton, secretary of agriculture under Grover Cleveland, founded Arbor Day. Celebrated on the last Friday in April, the holiday is simple: Just plant a tree. On the first Arbor Day in 1872, a million-plus trees took root across the United States. No doubt many of them survived the odds and still shade our city streets and backyards. But those are just babies.

Some trees in our region have escaped the ax, lightning bolt, steamroller, and hurricane for a stunning number of years. And these "monument trees" tend to stir up sentimentality. There's the Balmville Tree in Newburgh, N.Y, the oldest eastern cottonwood in the eastern U.S. Harvard University scientists estimate it to be more than 300 years old, almost as old as Harvard itself. The usual life expectancy of cottonwoods is about 85 years. This monument tree lives on a small piece of protected land—in fact the smallest state forest in New York (348 square feet)—its trunk now hollow, several of its branches secured by steel cables.

The Washington Oak, in Princeton Township, N.J., witnessed British and American troops fight the 1777 Battle of Princeton and has long been a popular tourist attraction. In the 1980s development threatened the mighty white oak, but supporters fought for its cause. Today it stands on a protected piece of open space in the middle of a mixed-use housing development.

New York City's tallest and oldest living resident lives in more obscurity. The Queens Giant, a 134-foot-tall and, some say, more than 425-year-old tulip tree, is a neighbor of the Douglaston Plaza mall and the Long Island Expressway. No signs identify it and passersby don't tend to linger in Alley Pond Park, near where the Giant is surrounded by a chain-link fence and a grove of younger tulip trees.

"People tend to view trees as permanent fixtures," says Tchukki Andersen, staff arborist at Tree Care Industry Association in Londonderry, N.H. "People get attached to them because they're always there," she says. "Those in our profession understand the life cycle. Trees live, grow, change, get old. Everything has a shelf life."

But the monument trees often receive special treatment. "It's difficult to accept that this old monument will fall and become part of the soil," says Andersen. And so band-aids like cables and other props come into play.

Ironically, it's the attention we give to a tree that can stress it the most. "The tree basically wants to be surrounded by other trees," she says. "Those with soil, birds, and animals around them have it easier."

When humans, vandals, machines, and pavement enter and "tree associates" are removed, says Andersen, "that tree has to support itself." While we worship the witness to so much human history, she says, the monument tree might be saying, "Oh, where is the forest duff to feed my roots?" Perhaps that independent spirit makes their survival even more poignant.