In the rain they come, groups of older women, mostly, and mothers with teenage daughters. Their umbrellas are bright and patterned, but they cannot outshine the flowers.

Since Helen Dillon announced she was leaving 45 Sandford Road after 44 years, the visitors have been crowding into Ireland’s most famous private garden for one last horticultural feast before it closes on the last Sunday of September. Dillon and her husband, Val, have sold their Georgian house and the half-acre garden in Dublin’s trendy Ranelagh neighborhood and plan to retreat to a smaller abode.

Like the Dublin rain, visitors pour into Helen Dillon’s famed town garden for one last feast. Dillon plans to close the garden permanently at the end of the September. (Adrian Higgins/The Washington Post)

Soon, the celebrated Dillon Garden will retreat, too, and in private, as the new buyers convert much of the heart of the garden back to lawn. Dillon will gather her plants in pots, which must number hundreds and range from tiny cuttings in two-inch containers to her beloved potted hagenias, a sumac-like tree from Ethiopia.

Robin Lane Fox, in a 2014 column in the Financial Times, described the Dillon Garden as “the best walled town garden one can hope to see.” Note to the world’s garden lovers: Hurry.

Around the spine of a descending Moorish fountain and canal, the garden is a harmonious medley of tender and hardy plants from five continents, planted in highly considered combinations. There are no trendy plant habitats or faux ecosystems, but intense, artful compositions. It reveals Dillon as a master plantswoman and a skilled colorist, which is a dying art.

Dillon is a master at the art of colorful floral combinations. Here, she has combined brugmansia, tibouchina and alstroemeria. (Adrian Higgins/The Washington Post)

The plants are not labeled, and many may be known only to connoisseurs, but this is the garden’s charm. I don’t think I have seen another garden where so many diverse plants — bulbs, tropical vines, tender perennials, shrubs, herbs, succulents, annuals — are interwoven so densely, seamlessly and effectively. The heavy reliance on containers, some obscured, others not, allows Dillon to move things in and out of season and to adjust heights.

In one part of the central border, she paired a pink brugmansia with an intense magenta alstroemeria and a royal blue Tibouchina urvilleana.

Elsewhere, she used light and dark varieties of agapanthus in a blue border, the hue repeated in the towering blooms of aconitum. Peeking from below was a hydrangea whose white florets were aging a rose color that harmonized with the blues. God is in the details.

Among the extravagant oddities was a shrubby tender vine whose common name, monastery bells, speaks to its big, squat campanulate flower, unlike any other I have seen. It grows in and around a red-barked slender tree named Arbutus x andrachnoides.

The couple came to the property from London in the early 1970s. One of the first things Helen Dillon did was to remove an incongruous but period-trendy rock garden, and then she made the decision — a blunder, she admits — to erect an antique iron fountain as a focal point, now long gone. The central canal and its dark limestone frame came later, and apart from its utility, it gives the garden some structure to temper the parade of plants.

The water brings light down from the sky and spreads it around like a croupier dealing cards. In Dublin, summer days are long but not necessarily bright.

The great design challenge in a town garden, even one as generous as this, is to address the dominance of its rectilinear boundaries. Here, the edges are blurred with sub-gardens, including an arid-looking corner consisting of a grove of aralia trees underplanted with ferns and tropical shrublike plants resembling justicias. It sounds a bit wacky, but it is this inventiveness that has given the garden its originality and its edge. If Dillon seems driven to a point of obsession, the garden merely affirms that.

In one edge, near a raised-bed garden marked by a sundial, she has a handcrafted aviary stocked with a few zebra finches, a flock of orange canaries and, if you are still, a furtive mouse that darts out to feed.

Closer to the house, two small greenhouses offer shelter from the drizzle and a look at more plants in pots — including regal geraniums and more ferns. It is here that Dillon, originally from Scotland, has spent long and absorbing hours over the years, starting new plants from seeds and cuttings.

The two small greenhouses offer a propagation center for Dillon, and a place to store tender plants in winter. Here regal geraniums are set close to a tree fern. (Adrian Higgins/The Washington Post)

She has written several books about the garden, co-hosted a popular garden show on Irish TV for several years and has done the lecture tours wide and far. “I’ve been to 27 states, including Alaska,” she said, handing me a cup of tea. I had talked my way into her cozy kitchen, out of the rain, for a chat. We had met years ago in Richmond, but I’m not sure she remembered.

She’s now in her 70s, and gardening at such a pitch takes its toll on the body, even with some help. Her plan was to let the garden fade with time, and in great age she would merely observe its decline from within the house, which was built in 1830. But last winter, the couple made the decision to downsize.

It seems hard to think of such a dynamo winding down, and when pressed, she says the new garden will get the creative juices going again, even if she has no plans to open it to visitors. Her plant-driven, consummate approach, she concedes, “is labor-intensive, which is very unfashionable.”

The Washington Post (Adrian Higgins)

Over the years, she has done major reworkings of portions of the Dillon Garden, which opened to visitors 25 years ago. The front garden is a strikingly restrained composition of a stone terrace and birch trees. But there’s nothing left to redo. “It has got like an overpainted picture. It’s not fresh, and I can’t think of anything else to do with it,” she said. “I want to play somewhere else.”

Another consideration is that an intensively cultivated garden runs out of steam even if, like Dillon, you use only organic feeds. The soil is depleted, and the pests and diseases have built up. It was time to move on.

“I don’t want to be a curator,” she said, “I want to be a creator.”

Asked how he felt about the end of the era, Val Dillon, who has served as his wife’s garden helper all these years, chose church Latin over the botanical kind. “Deo gratias.”

More from Home and Garden:

A shrub to brighten the dog days of summer

Rekindling a gardener’s passion for daylilies

Birds, chipmunks, snakes, insects: At some point, the gardener feels like an intruder

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