How One Couple Turned Their Backyard Into an Arboretum

This is what happens if you stay put, and keep digging holes: An effort that begins innocently enough — planting a garden at home — may grow on you. And it could morph into an arboretum.

Hortus Arboretum & Botanical Gardens, a 21-acre expanse in Stone Ridge, N.Y., with about 11 acres under cultivation, got its start as Allyson Levy and Scott Serrano’s much smaller backyard. It has been 25 years since the couple, both visual artists, moved from San Francisco to Ulster County, where they now count more than 240 genera in their plant collection.

And it all began, as most gardens do, by making space for irresistible finds from local nurseries — no master plan involved.

More than a few were plants that bore fruit.

“Scott was channeling his inner bear, planting a lot of berry plants,” Ms. Levy recalled. They both favored species whose leaves or seeds might inspire their artwork.

A few years in, with a young family and a budget to consider, she forced a reckoning, voicing the concern that they should focus their gardening efforts. “If we’re going to plant salvias,” she proposed, “let’s just have different species. If we’re going to plant anything, let’s start thinking about an overall design, and how we’re planting and where.”

Before long, they had exhausted the possibilities at nearby garden centers and began ordering tiny rooted cuttings of shrubs and trees from rare-plant nurseries. Others, they grew from seed — even trees.

They once lived three blocks from Strybing Arboretum (now the San Francisco Botanical Garden at Strybing Arboretum). That was “our first really hard-core introduction to trees,” Mr. Serrano said. “And we have planted a lot of what we saw there. A lot of that stuff lingers in our heads.”

An early visit to Brooklyn Botanic Garden made an impression, too.

“I said, ‘Oh, I would like a house dropped right here,’” Mr. Serrano recalled. “I wanted more fruit trees and more things I can eat, but I wanted a house dropped in a place like this. And so we set about just surrounding our house with an arboretum, slowly.”

At first, it was a process that he acknowledged was “sort of reckless.” But pretty quickly it became systematic, with proper record-keeping.

By 2009, the couple had added an eight-acre parcel across the road from their original three-acre yard. By 2012, they had applied for accreditation to the Morton Arboretum’s ArbNet, a registry of woody plant-focused collections and public gardens. Their arboretum, a nonprofit organization since 2019, is now open on weekends and by appointment through mid-November.

Collections Within the Collection

Early on, themes began emerging: They amassed a diversity of Chinese plants, and of hardy cactus. They went deep into beloved genera, collecting various Stewartia trees (a dozen in all); magnolias (about 20); and viburnum (more than 30). They also had lots of plants that were good to eat.

Many of those edibles became the focus of the couple’s 2022 book, “Cold-Hardy Fruits and Nuts: 50 Easy-to-Grow Plants for the Organic Home Garden or Landscape,” which profiles their successful selections from around the world.

That includes native fruits like pawpaw (Asimina triloba), American persimmon (Diospyros virginiana), chokeberries (Aronia) and juneberries (Amelanchier).

But many are from much farther away and are much less familiar, including real oddities like Himalayan chocolate berry (Leycesteria formosa), a showy shrub related to honeysuckle, with a small fruit they describe as tasting like “dark chocolate, espresso, burned caramel and blackberry — all at the same time.”

Its self-fertile flowers, produced from spring through fall, are surrounded by burgundy bracts that are particularly flashy when set off against the gold leaves of the cultivar Golden Lanterns.

Another honeysuckle relative, honeyberry or haskap (Lonicera caerulea), is an exceptionally hardy shrub with a circumpolar native range in Asia, Europe and North America. Its fruits, among the earliest ripening, are distinguished by their blue color. Because honeyberry is not self-fertile, two varieties with overlapping bloom times are required for cross-pollination.

In the book, the couple describe their arboretum as “an aesthetically arranged experiment station to test interesting and useful plants.” They don’t hesitate to push zones (the chocolate berry, for instance, is rated as Zone 7, but they do fine with it in Zone 6 by using winter mulch). They take a special interest in endangered plants, including natives like Stern’s medlar (x Crataemespilus canescens), a naturally occurring hawthorn-medlar hybrid from Arkansas, and the Virginia round-leaf birch (Betula uber).

What there aren’t a lot of are the usual fruiting suspects: the peaches, apples and plums that, although familiar, are not so easy to grow by the organic practices they follow, at least not in the Northeast.

“If you plant a peach tree in our environment,” Mr. Serrano said, “it’s like going to war. You sit back, and you wait to be attacked over and over and over and over.”

The common European pear tree (Pyrus communis) can also be susceptible to disease in the Northeast and can take a decade to reach fruiting age. Instead, they suggest trying an Asian pear (mostly hybrids of Pyrus pyrifolia), many of which are more disease resistant and bear fruit younger.

But if you’re planting an Asian pear, you’ll have to plant two, as Asian pears are generally not self-fruitful; cross-pollination by another variety that blooms concurrently is needed. For smaller gardens, there’s a workaround: Specialty nurseries sell combination or multi-grafted trees, with several varieties on a single plant, satisfying both the pollination requirements and the gardener’s appetite. The arboretum has a multi-grafted specimen of the flavorful varieties Chojuro, Yongi and Kosui.

Medlar and Goji Berry, Magnolia Vine and Che

If you’re planting medlar (Mespilus germanica), you’ll need to make room for just one to get a harvest.

Ms. Levy describes the self-fruitful rose family member, a relative of quince and apple, as “a beautiful, gnarly looking medieval tree” of rounded, shrubby stature, reaching maybe 15 by 15 feet. Its large, camellia-like white spring flowers are followed by one- to two-inch russet-colored fruits.

Figuring out when the fruit is ripe enough to eat, however, is a bit of a puzzle. It isn’t until well after the thick, shiny foliage goes butter-yellow in the fall and drops. What is required is a period of bletting: achieving an overripe state just short of rotting, manifesting an applesauce-like consistency and flavor inside. Frost exposure can help, as can a storage period.

One species in the Hortus collection more commonly found in health-food products than gardens is goji berry (Lycium barbarum), which has a long history in traditional Chinese medicine. Thankfully, it fruits on new wood, because pruning is required to keep it from being too messy.

“It’s a vine kind of disguised as a shrub, or a shrub that’s disguised as a vine,” Ms. Levy said. “It doesn’t quite know what it wants to be.”

Their solution has been to plant the small, fountain-shaped shrub where it can drape over a bit of stone wall. Goji flowers will self-pollinate, but a heavier crop of the fruit — which tastes like a combination of cranberry and licorice, and is sweetest when eaten dried — results when you plant more than one shrub.

The berries of Schisandra (S. chinensis), the magnolia vine, appear in records of Chinese medicine from more than 4,000 years ago, the couple write, but the plant is almost never seen in American gardens or catalogs. The vine, which needs a trellis or other support and a spot in partial shade, produces grapelike fruit clusters tasting of “lemon peel with a little bit of berry,” Mr. Serrano said. When sweetened, he noted, they taste something like strawberry lemonade.

Schisandra is naturally dioecious — the plants are either male or female — so at least one of each is required to produce fruit. But the cultivated variety Eastern Prince is reliably self-fertile (and can be found at Logee’s Greenhouses, among other specialist nurseries).

Another little-grown fruiting tree that Mr. Serrano and Ms. Levy hope more people will try: che, or Chinese melon berry (Maclura tricuspidata). Take the flavor of mulberry and fig (both che relatives), and add watermelon and lychee, they said, and you approximate the taste of these fruits, which ripen in October and resemble those of the kousa dogwood (Cornus kousa).

To get around the pollination issues of the male and female plants — and to avoid a mouthful of seeds — seek out a seedless, self-fruitful female variety.

The arboretum’s edibles list goes on — it also includes lingonberries, gooseberries, quince and more — and is not limited to woody plants. Despite warnings that they are too tender for Zone 6, the couple have succeeded in getting myoga ginger (Zingiber mioga) and wasabi (Eutrema japonicum) to grow as perennials at the arboretum.

Not everything works, of course, and sometimes they must let go. Various of those needy, disease-prone Prunus — plums, cherries, sour cherries, peaches — have been felled since last October to make way for a meadow, another extension of Mr. Serrano and Ms. Levy’s botanical education.

Visitors will often point to some specimen and lament, “I tried to plant that, but …”

The couple’s answer is invariably the same: “How many times?”

“Most of our learning is really by doing and failing, sometimes failing several times,” Ms. Levy said.

Eventually, they figure out a plant’s needs, she added: “You’ve done your homework; you’ve seen how it grows in a certain spot.”

Perhaps one of their plants would flourish in a corner of the expanding collection in your own backyard?

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

If you have a gardening question, email it to Margaret Roach at gardenqanda@nytimes.com, and she may address it in a future column.