The naturalistic landscapes that Donald Pell creates meet with approval from such discerning constituents as pollinators and birds, and seeing and hearing their feedback delights him in return.

But when Pell begins to conceive the transformation of a space, it is always with another demographic squarely in mind, he said: “How do we make it a habitat for humans as well?”

Pell’s objective as a designer is an immersive landscape that invites us to engage — one we intuitively understand how to interact with, not simply look at.

“I want to live in these places that I can move through and explore and be in,” he said, adding that a successful landscape is “not just this thing that you see, it’s this place you live in.” We touch and smell the plants and hear the birds, he said, making “multiplicities of connections that you are now part of.”

At first glance at one of his effusive, wild-ish landscapes, an observer might guess Pell works in natives only. Although many figure in his designs, he is “not the native plant guy,” he is quick to point out — not a purist.

Instead, he makes the case for a wider palette, one that includes “the joy of cosmopolitan plants,” which he says “have been demonized.” (Pell and others use the term “cosmopolitan” to mean distinguished plants from many parts of the world.) We needn’t be botanical absolutists, he contends, to successfully serve resident and visiting humans and wildlife alike.

A garden “can be wild places, and be about people first, and be about native plants and include cosmopolitan ones,” he added. “It can be all of these things.”

Pell does not use nonnatives that have proved invasive. But at the East Vincent, Pennsylvania, headquarters of his landscape design studio, on a 14-acre former farm he bought in 2008, he welcomes plants from many homelands in the gardens.

He wouldn’t be without woodland sage (Salvia nemorosa), a European and west-central Asian species whose bold swaths of purple start in early summer. The compact cultivar Wesuwe and the larger, more open East Friesland are two favorites.

The current scene is enlivened by native asters, including the smooth aster (Symphyotrichum laeve) and the heart-leaved aster (Aster cordifolius), plus a hybrid called Twilight. Intermingled with them, nonnative moor grasses (Molinia) play a big part in autumn’s success, offering “spectacular fall colors of rich mango that explode in late October,” he said.

All around, seedheads of various perennials, a feature he says he “obsesses about,” are starting to form.

In a shady corner, the orchid-like flowers of Tricyrtis Sinonome, a hybrid toad lily of Asian origin, could seduce even the most devoted nativists. “Nobody doesn’t respond to it,” he said of the plant, whose white blooms are spotted with burgundy-purple.

The studio’s gardens and nursery area are where Pell experiments with building what he calls “novel plant communities” — plant combinations not found in nature, but which he imagines might be visually appealing. Will they work, though, and really prove to be good long-term partners? Before they are drawn into a design, he needs to know.

One that got a resounding yes: Panicum Shenandoah, a cultivar of native switch grass (P. virgatum), paired with the tall, airy meadow rue from Japan (Thalictrum rochebruneanum), sporting loose sprays of tiny lavender bells.

At the farm, he can test-drive such ideas and trial newly introduced or otherwise unfamiliar plants, culling any that don’t perform or that misbehave.

Clients visit, too, to get a feel for how Pell’s dynamic landscapes work, and what goes into their continuing care. Showing his guests around, he is able to offer real-life examples of how things will evolve, since static artworks these are not.

Editing as an art form

Pell wants one thing to be understood: Editing will be required (and some spots may require rethinking). Despite his practice of planting densely, to reduce weeds, he has faced such inevitabilities in each of his 31 years in the business, and shares tactical wisdoms acquired along the way with whomever will be caring for any garden he designs. The conversations continue once or twice each year even at properties his crew isn’t helping to maintain.

His role is to listen to what’s happening and suggest options for next steps, explaining the possibilities so the garden’s humans can decide in which direction they want to nudge the picture in front of them. There is no one right answer.

“Gardeners really become the designers of the future,” he said. “Depending on how the composition is put together, things are going to sow freely and they’re going to move around, and those folks get to decide what they’re going to allow and not allow.”

There are obvious weeds to remove — he loves a hori hori knife for removing roots and all — but this aftercare role, he stressed, is more than a maintenance job.

“Editing is a real art form,” he said.

Like the garden itself, he is a voice inviting us to engage and explore.

“I think my message is just like: ‘Go put plants in the ground. See what you like, put them in the ground, and play, and fail,’” he said. “And that’s OK, that’s just as exciting.”

Exciting, if at first a little counterintuitive, Pell knows. The looseness of naturalistic landscapes, compared with the formality of traditional ones, contributes to the impression that they are lower-maintenance. “I hear that often: ‘Oh, native plants are easier,’” he said.

Plants of any origin are competitive, and some are outright bullies, which is why he does that trialing and testing. He strives for combinations based not just on looks, but on where the component plants’ inherent competitive natures match, too.

That doesn’t mean they won’t still need some editing.

“You might just be left with a monoculture if you don’t intervene,” he said. “Even native plants are not just ‘set it and forget it.’ If you want a dynamic planting, you’re going to have to decide to intervene. And that’s gardening.”