When the High Line at the Rail Yards, the final section of the elevated park, opens on Sept. 21, we will no longer have to stop at 30th Street and stare longingly through the construction gate at the Queen Anne’s Lace blooming in wild profusion along the old tracks.

We can walk out on a wide plaza made of the familiar concrete planks, tapered so that plants appear to be pushing up out of the crevices. It’s the same planking system that flows from Gansevoort Street, a mile south, where the High Line begins in the heart of the meatpacking district, in the dappled light of a birch grove.

© Todd Heisler/The New York Times

The northernmost $75 million section has the same benches, too — modernist perches, of reclaimed Angelique, a tropical hardwood, and precast concrete, that appear to peel up from the floor. But now, they have morphed into picnic tables and even a seesaw for children, as one heads west, along a grove of Kentucky coffee trees toward the river.

Quaking aspens, their leaves rustling in the slightest breeze, rise out of beds full of sumacs, sassafras and the countless prairie plants and grasses that Piet Oudolf, the Dutch master plants man envisioned here. “It’s still lush, still natural, but we used different trees and other species,” Mr. Oudolf said on the phone from his home in Hummelo, the Netherlands.

The wild, untouched section is reached only after crossing the 11th Avenue bridge, where a wide central path rises gently over seven lanes of streaming southbound traffic, and lifts the heart with its dramatic views up and down Manhattan’s grid.

It is a relief to leave behind the old tamed High Line, truly a garden now, complete with a lawn. (Couldn’t lawn lovers just go over to Hudson River Park?)

After the bridge, the joy is gazing upon unruly plantings, left by the birds or the wind, growing out of the rusted track: chokecherry, laden with berries, milkweed pods bursting with seeds, evening primrose and blazing star, even a crab apple tree fruiting in the middle of a sea of Queen Anne’s lace.

Working with the designers — James Corner Field Operations and Diller Scofidio & Renfro — Mr. Oudolf had created meadows and shady woodlands, a kind of call and response to the sunny openings and architectural canyons traversed by the entire High Line.

But now, as the tracks curve westward at 30th Street, there is more of a visceral sense of those freight cars that once rushed straight for the Hudson River, before taking a sharp right turn at the West Side Highway and shooting north to 34th Street. The wide open feel of the plaza at 30th Street quickly shifts to a westward journey. At first, sections of original rail track, with new wood ties filled with bonded aggregate, form a smooth walking path. After the bridge, you find yourself on a path with rusted rails and weathered ties, running along the untouched, self-seeded landscape all the way.

“We haven’t pruned a thing,” said Tom Smarr, the director of horticulture for the Friends of the High Line, as we gazed at a crab apple tree, heavy with fruit. “We’re going to do very little here.”

It’s the spirit of the old railroad that Mayor Rudolph W. Giuliani wanted to tear down in 1999 when nobody loved it, except for a few graffiti artists and street people, and others drawn to industrial ruins. It was a romantic, forgotten place, but once it became a park, it had to support the weight of the five million people who now flock here annually.

Most of them think they are walking through a “wild” tapestry of plants that came here on their own. That’s how good Mr. Oudolf is. But, of course, the grasses and fabulous flowering plants and vines, the magnolias and shad trees, the groves of gray birch, are planted and tended by many human hands, not the unconscious random hand of nature.

“It’s not wild at all,” Mr. Oudolf said. “It’s an introduction to the wild.”

Apparently enough of us have missed that old sense of the High Line to want a piece of it back.

“We’ve had a lot of feedback from the community saying, ‘We want to walk on the original tracks,’ ” said Megan Freed, communications director for the Friends.

But you had better come see it while you can because the Friends call it an interim walkway.

“A time will come when we’ll have to do some of the things we did on the rest of the High Line,” said Josh David, president of the Friends, “in terms of removing the original landscape, stripping the steel work of lead paint, restoring the concrete” just to make this public park structurally sound and safe.

Mr. David and Robert Hammond founded the Friends in 1999, persuading the city to see the hulking steel dinosaur of New York’s industrial past as a powerful symbol that could be transformed into a new kind of park, deep in the city, yet hovering above it.

“I think for Robert and me and a few people who did spend a lot of time up in the original landscape, there will be a nostalgia for that lost place, which is one reason that the rail yard section is so exciting to us,” said Mr. David, who sat down next to Mr. Hammond at his first community meeting 16 years ago, because he thought Mr. Hammond was cute.

The new section also responds to another frequent request from the community: more activities for children.

“I was behind a family the other day, and the kid kept saying, ‘Can we go now?’ ” Mr. Smarr said on our afternoon walk.

Now, a section has been cut out of the steel structure, so that children and adventurous adults can explore the maze of girders and beams (covered with thick rubber safety coating).

The Rail Yards section affords a whole new set of experiences. People can look down on the expanse of commuter trains lined up below in Hudson Yards. They can eventually walk east, at 30th Street, beneath a vast colonnade to a forested spur that will span 10th Avenue. Coach is building the first of the skyscrapers that will hem in the sky, as the 26-acre, $15 billion Hudson Yards district proceeds.

All the more reason to enjoy the Rail Yards section of the High Line now.

“Something magical happens closer to the river,” Mr. David said.

It’s magical where the so-called weeds grow, too. Why make it an interim path? There are so many plants on the rest of the High Line, you have to look hard even to see the tracks.

Mr. David thought about that for a moment. “In theory, you could let it happen all over again,” he said of those plants that grew on their own, between the tracks. “Do the repairs, put the gravel ballast back and let it happen, like it did before.”

He didn’t think New Yorkers would want to wait around for that.

But I say: Let them wait. Here’s a little piece of the wild High Line worth keeping.