Every year about 37 million people go to Central Park, and, finding themselves surrounded by 23,000 trees, most do not know their sassafras from their euonymus.

But Ken Chaya and Edward Sibley Barnard are not like most people. Spend two hours walking Manhattan’s oxygen-infused oasis with this pair and it’s as if all of your senses are on steroids.

You smell the fresh wintergreen scent of a sweet birch branch split open. You pick up a crusty pod from the Kentucky coffeetree and taste the molasses-like jelly inside (but not the seeds, which can be toxic if they are not cooked). You run your hands over the winged branches of the Euonymus alatus and they feel like cork.

And then you begin to understand the pure wonder that drove these two men to give up two and a half years of their lives to make a map that details 19,933 trees in Central Park.

The map includes 174 species and represents about 85 percent of the vegetation on the park’s 341 hectares.

“Do I want every tree?” asked Mr. Chaya, 55, a birder and freelance graphic designer. “Of course, but I’m crazy. You can’t have every tree. There’s great hubris in wanting every tree. But we got the big ones, we have the important ones.”

The pair said they had spent nearly $40,000 on the project because they cherished Central Park. They hope only to earn back their expenses.

The two-sided, waterproof map, called “Central Park Entire: The Definitive Illustrated Folding Map,” is sold for $12.95 at a giftshop in the park and on the men’s Web site, CentralParkNature. com. They have sold about 1,100 copies of the $35 poster version since January.

Mr. Chaya drew the features, including trai ls, monuments, bridges and playgrounds. All restrooms are noted.

The map, said Mr. Barnard, who is called Ned, was his idea. He wanted to write a book about the trees of Central Park and enlisted Mr. Chaya, a friend since the 1970s.

But once Mr. Chaya delved into the thicket of the Ramble to sketch a sample, the two realized they had a bigger product, one more immediately useful. Just inside the Inventors’ Gate at 72nd Street and Fifth Avenue, Mr. Barnard pointed to a diverse group of about 20 species, including the magnolia, the hornbeam with a sinewy bark, the stately American elm, the omnipresent black cherry (there are 3,839 of those on the map), the buckeye, and the invasive Norway maple, which Mr. Chaya jokingly called Eurotrash because it aggressively took resources from other species.

In the foreground was the London plane, the favorite of Robert Moses, the urban planner who had it planted all over the city, thinking it was a sophisticated British tree. It is a garden hybrid, Mr. Barnard said. In any event, its leaf remains the symbol of the parks department.

Near the Conservatory Water, Mr. Barnard and Mr. Chaya eagerly pointed to three mature pin oaks, each leaning like the Tower of Pisa toward a slice of sun.

“Their powers of observation are tremendous,” Neil Calvanese, the vice president of operations for the Central Park Conservancy, said of the mapmakers. The Conservancy is the nonprofit organization that manages the park and raises 85 percent of its $37.4 million annual budget.

Mr. Calvanese has worked with trees in Central Park for 30 years, but the men told him about a chestnut oak in the North Woods that he had never seen. “It kind of bothered me,” he said. “I should have known that.”

Since the poster came out, Mr. Calvanese has overseen the removal of nearly 70 precarious trees on that map; that task is an important part of the Conservancy’s work, since falling limbs over the last two years caused two deaths . The organization is also still trying to fill in a northern section that lost more than 500 trees in a storm in August 2009. The folding map reflects 303 new trees.

Only about 150 trees are left from the era of the park’s designers, Frederick Law Olmsted and Calvert Vaux. One from around 1862 is a favorite of Mr. Barnard’s: the black tupelo, sitting in its own meadow in the Ramble, the park’s woodland area. “Old trees have a sacred element for me,” Mr. Barnard said . “They created us. We’re all mammals that spent our time in the canopy.”

Mr. Chaya said he considered the park one of the most important masterpieces of American art. “And to me,” Mr. Chaya said, “masterpieces never smell this good.”

But masterpieces are eternal and Central Park is forever changing . Leaving the Ramble the other day, the men spotted a hollowed stump of a black cherry, just recently cut down.

“This is an example,” Mr. Chaya said, “of the map that’s never finished.”


By LIZ ROBBINS