On a recent visit to what remains of the Losh Run plant, Chris K. Firestone, wild plant program manager with the Pennsylvania Bureau of Forestry, said it was important to protect such long-lived plants because they might possess survival secrets that have yet to be identified.

“There are so many relationships between plants that we just don’t know about,” she said. “If we lose something, it could be something important.”

In the box huckleberry, one such secret lies underground.

The plant is considered self-sterile — it cannot fertilize itself with its own pollen — and relies on similar box huckleberries around it to reproduce, Dr. Pooler said. But it is something of a loner, growing in dry spots isolated from other plants like it.

Without pollination, it sends out underground runners that produce genetically identical shoots, or clones, spreading an average of six inches a year until it covers an immense area. (A box huckleberry’s age is calculated by measuring its spread and dividing by six.)

Although their long life makes these plants notable, accepting their age based on root material means adopting a unique perspective on what it means to be old. Back in 2004, Alan S. Weakley, director of the University of North Carolina Herbarium, accompanied Mr. Bloodworth to the site of his discovery and confirmed that it was indeed box huckleberry.

Dr. Weakley said he was somewhat uncomfortable comparing the plant’s age to that of ancient trees, whose rings make their age irrefutable.

“Yes, the huckleberry is the same genetic individual, a clone and all,” he said, “but to me, that’s less impressive than looking at a single trunk of a single tree and saying this trunk is 4,000 years old.”