Plants are flopping, and leaves are dropping; the garden is letting go. But while we may have the urge to check “garden cleanup” off the to-do list with one heroic push, it’s not like “mop kitchen floor.”

There’s a valuable education, and a lot of life, tucked between and beneath all those fading bits.

As Peter Bevacqua, a garden designer in Claverack, N.Y., has learned, a conscious cleanup can yield site-specific, garden-improving ideas — and also seasonal snippets you can bring indoors, to savor a little longer.

Get out your notebook: It’s prime study time.

Mr. Bevacqua has been watching, and occasionally assisting, as things unfold in the two and a half acres of formal gardens and wilder plantings that he shares with his husband, Stephen King. In 1988, the two former advertising creative directors bought the 1920s colonial-style house on a flat piece of land outside Hudson, N.Y., as a weekend place. For about five years now, it has been their full-time home.

For Mr. Bevacqua, whose father taught him to garden when he was a child, being upstate has meant liberation from the frustrating constraints of a few window boxes outside the couple’s former Upper West Side apartment.

Tentatively at first, they set about making a formal landscape — Mr. King making his mark with hardscape projects and crisp edging, Mr. Bevacqua with plants and more plants.

They laid a winding brick path to a greenhouse the previous owner built not far from the main house, and planted a long border there. “Or at least it seemed long to us in those days,” Mr. Bevacqua said of that first project.

Tentative turned to adventurous, and long came to mean longer, after Mr. Bevacqua did a two-week, hands-on training at one of England’s best-known gardens, Great Dixter, in East Sussex. He has returned five times, calling himself a proper “Great Dixter groupie” in his Instagram bio.

That connection shows. At the heart of the couple’s place is the sun garden, a rectangular room defined by yew hedging that gets shorn in early July. Within it are gravel pathways and effusive flower beds.

Inside the hedges and beyond, theirs is a world studded with boxwood globes and topiary, from oversized muffins to giant green wedding cakes. It has been a popular Garden Conservancy Open Days destination for 15 years and is one of 20 gardens profiled in the new book “American Roots: Lessons and Inspiration from the Designers Reimagining Our Home Gardens,” by Nick McCullough, Allison McCullough and Teresa Woodard.

Things Are Looking Up: Think Vertical

In the fall, as clients’ landscapes and his own quiet down visually and show their bones, Mr. Bevacqua is recording what worked and what didn’t, before all evidence is erased. He will make the rounds, ensuring that strategically placed planting pockets are left open, prepped and ready to receive bold, tender things in spring’s planting frenzy — perhaps dark-leaved cannas or seedlings of red-leaved castor bean (Ricinus communis).

He will be checking on certain energetic perennials that his compositions rely on: Without editing, they will overgrow their territories, throwing off the weight of a design. Cup plant (Silphium perfoliatum) and Tatarian aster (Aster tataricus) are on that list, reduced now or noted for spring division.

But there are subtler cues to watch for, too — including where you might “co-opt a view,” he said. One example: a neighbor’s giant Crimson King maple, he said, is “a big kind of purple blob I use as the background for a couple of our garden scenes.”

Look beyond, and look up: Because of his visual background, Mr. Bevacqua knew that juxtaposing shapes — mounds, pyramids, columns — would make for more dynamic garden compositions. But for years, he didn’t grasp the full potential power of the vertical, which has become a signature of his designs.

“I kind of did it before the impact it could have came to me,” he said. “I was so busy looking down, I never thought I could change the elevations of this flat piece of land — but I realized I could, in the air.”

The reveal conjured the architecture of an old church, he said: “There are always these wonderful columns that lead your eye up to the heavenly host or something up there. And I could move the garden that way. That was a big ‘aha’ for me.”

Now whenever he looks at a prospective job or reviews a landscape in progress, he asks himself, “Which vignettes or views here could use a vertical?”

Layer Upon Layer

In his own garden, Mr. Bevacqua has made room for many columnar elements in addition to the classical, architectural ones, including a sweetgum tree (Liquidambar styraciflua Slender Silhouette) and a purple-leaved European beech (Fagus sylvatica Red Obelisk). Even that Silphium, a prairie native reaching 10 feet, is kept upright and exclamatory by a long-legged metal support that he had custom made.

Other early efforts included sheathing the garage in not just vines, but also a shrub, variegated Euonymous. It is trained flat up one wall, mingling with Boston ivy (Parthenocissus tricuspidata) and Dutchman’s pipe (Aristolochia).

How do you make a shrub behave like a climber?

Plant it right next to the wall and cut off anything that comes toward you, Mr. Bevacqua said. As it grows, keep removing anything that’s not headed upward, until the plant gets the idea.

Layering plants to create intimate partnerships, rather than planting a single one on its own, is another favorite tactic. And he scouts for possibilities: What shrub might serve as armature for a Clematis vine? Which tree could support a climbing hydrangea (Hydrangea petiolaris)?

Take a Walk on the Wild Side

An opportunity to add habitat and create a contrast to the formality the couple had cultivated presented itself five years ago, when an adjacent quarter-acre lot became available. It was the beginning of their nearly wild garden, and offered a place for an introduction to beekeeping.

“It was an old lawn that just went wild,” Mr. Bevacqua said. “And tons of invasives came in.”

How to subdue them without herbicides, making way for enhanced diversity? The competition was too fierce for sowing the seeds of desirable species. Even small seedlings plugged in wouldn’t take, either.

Keeping the unwanted vegetation cut back, Mr. Bevacqua began introducing large plants. Successes include Baptisia, goldenrods (Solidago), asters and Phlox paniculata Jeana, as well as winterberry hollies (Ilex verticillata). Some too-energetic edits from the formal areas, including the Silphium and Tatarian aster, are also finding homes in the nearly wild garden.

“It’s sort of an experiment,” he said. “But the key, for me, was just planting things that were large.”

Plan for Some Movable Color: Potting Up Bulbs

Even the best-planned garden needs props — movable elements to call into service as needed.

Outdoor furniture can complete a picture. Mr. Bevacqua placed four red chairs halfway between a dogwood (Cornus florida) and a big urn on a pedestal filled with paddle plant (Kalanchoe thyrsiflora). Both the tree and the succulent turn reddish in the fall, so what would otherwise be a dead space becomes a few weeks of fiery, three-note harmony.

But Mr. Bevacqua’s favorite portable accessories may be his pots of bulbs, including the Casablanca lilies he will enjoy on the terrace next summer or plug into a dead spot in a border. Each fall, he pots up tulips and lilies, and waters them. The pots, covered with heavy screening to keep animals out, overwinter in the garage or the cool greenhouse, where they remain until they start to show some growth in early spring and are set outside.

The containers of tulips offer an extra benefit: They provide a botanical test drive, a way to sample a variety and figure out if its color or height is just right, before committing to putting a larger number in the ground.

Conscious Cleanup (and Some Guilt-Free Rewards)

As the garden has evolved, so has Mr. Bevacqua’s fall cleanup routine.

“I used to go at it sort of hammer-and-tongs to clean up things,” he said.

Yes, the red Abyssinian banana (Ensete ventricosum) still gets cut back hard and stashed in the cellar with other potted tropicals. But elsewhere, his orientation is now based on ecological horticulture tenets: Leave plenty of bird food standing, as well as a good base of leaf litter, wherever practical, to support overwintering beneficial insects and other organisms.

Only the formal areas get anything resembling an old-style cleanup. And even that is actually a series of mini-cleanups in the style called chop-and-drop, “making maybe five passes over the final weeks, so that the pieces are smaller and just settle in and decompose,” Mr. Bevacqua said.

It also means he isn’t caught short by a sudden hard frost, when lots of the garden is still standing.

He cuts the nearly native garden down in stages, too, but the final cuts there are made at least 12 inches high, leaving more overwintering habitat — including hollow stems that native bees may tuck into.

Some chopped-down gleanings don’t drop, exactly, but come indoors as the stuff of impromptu arrangements that merge vivid tropical foliage with native fall wildflowers. These arrangements brighten rooms — and the gardener’s spirits.

“If I make these little bouquets to bring inside,” Mr. Bevacqua said, “I feel less guilty about taking the garden apart gradually, when it still looks like it could go on.”

Margaret Roach is the creator of the website and podcast A Way to Garden, and a book of the same name.

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