It's also rare enough, says Maryland state forester Steven W. Koehn, that the state, like several others around the country, has placed it on a list of species that warrant special efforts at conservation.

"We can study it, take samples of its seeds and grow more individuals in our state facilities," says Koehn, adding that he doesn't believe, as some do, that the species has migrated north because of conditions caused by global warming, but that Maryland is simply at the upper reaches of its native range.

Swarth chuckles a little as his colleague waddles toward the stand of trees.

Reaves' boots sink in as much as a foot, making noisy sucking sounds as he staggers forward.

"That mud looks innocent enough at first, doesn't it?" Swarth says from the safety of the boardwalk. "The soft [stuff] goes down about 10 feet."

It's worth noting that, in fact, these aren't the first pumpkin ash trees ever spotted in Maryland. That honor goes to a few that arborists have seen near the Potomac River and in bottomlands inside Piscataway Park near Accokeek.

Problem is, they were so hard to reach that no one could measure them, at least to the standards set by Besley. The Jug Bay boardwalk happens to make these individuals accessible enough to catalog.

"It's the first example of a Maryland pumpkin ash that people can find and visit," Bennett says.

Why must the arborist get so close? Besley's method, still in use today, demands it. His formula for size incorporates a tree's circumference, height and crown spread (the distance its branches spread from the trunk).

A tree's point total is the sum of its circumference as measured in inches, its height in feet, and one-fourth of its average crown spread in feet. (For those interested in context, the state's biggest living tree, a silver maple in Cecil County, weighs in at a whopping 464.5 points; its smallest state champ, a poison sumac, has 53.)

Since this tree has already been officially measured, Reaves knows its details: its 58-foot height, 43-inch circumference and average crown spread of 26.5 feet gives it a points total of 108.

But it's hard to tell with the naked eye which is the champ. Reaves will find the one that's 43 inches around, and he and Swarth will mark that for future guests.

He finally slogs his way to a likely specimen and throws his tape measure around it at the height Besley prescribed: four and a half feet.

"This is it, Chris," he says with a look of triumph. "Here's our champion."

Workplace of wonders

In the course of the quest, it has been easy to lose sight of the glories of this place. But for a moment it comes clear.

Swarth points out a tiny tree frog that sits in the muck, chirping. A few feet away is a living example of adaptation: A tree that has fallen into the water has sprouted three slender trunks that reach straight up toward the sky.

Across the water, at marsh's edge, a white heron sits on an osprey perch, casting a regal glance.

"Look at that," Swarth marvels, still captivated by his workplace of 22 years.

Jug Bay, Anne Arundel's biggest park, is something of a paradox. If we weren't careful, we could damage it just by visiting. But thanks to this boardwalk and a system of carefully planned trails, it's possible to see all this at close range without taking anything away.