Ryan Spaulding, biological research aide at the U.S. National Arboretum, examines box huckleberry seedlings for a breeding program that seeks to increase the genetic diversity of the ancient plants. (Adrian Higgins)
Gardening columnist

The box huckleberry is a cute little plant related to both the blueberry and the cranberry. Its fruit is the color of a blueberry, a dusky indigo, but smaller and shaped more like a cranberry.

The flavor is something of a hybrid, too. “You think it’s a blueberry, but more sour,” said Ryan Spaulding, who could be found recently harvesting the summer crop at the U.S. National Arboretum in Northeast Washington. I will have to take his word for it, because the seed is so precious that I was politely denied a sample.

Spaulding is a biological research aide whose recent and methodical harvesting of the berries — they ripen sequentially and in their own time — represents something quite exciting in the world of plant biology, even if the magnitude of the event is not obvious.

In four long, concrete cold frames in the arboretum’s lath house, 14 separate populations of box huckleberry have been growing for the past decade. This has been an inconspicuous research project in part because the lath house — designed to provide shade for plants that don’t like it too sunny — is not in a public part of the arboretum. The plant itself is no showoff, but rather a low-growing, shrubby ground cover with glossy but small evergreen leaves. If you saw it in its native setting, it would be calm and reassuring. These passive elements are really important in any landscape; they lower the pitch and keep things serene.

This summer’s crop of berries has been the best to date, which for plant geneticist Margaret Pooler is great news. Each berry may bear several seedlings, and each baby box huckleberry, when it sprouts, will further enrich the gene pool of this plant. As they stand, the humble colonies in these cold frames represent not only the richest genetic diversity of box huckleberry on the planet, but also the richest in the entire life history of the species.

Margaret Pooler, research geneticist at the U.S. National Arboretum, with cold frames of rare box-huckleberry. (Adrian Higgins)

Much of this is down to the fact that the box huckleberry, Gaylussacia brachycera, is a botanical loner.

As with blueberry and cranberry, it is a native shrub of the heath family, but unlike them, it increases by creeping runners. A colony may fruit, but the berries contain no seed or are sterile. Because it spreads no more than six inches a year, botanists calculated that the largest known colony, in south-central Pennsylvania, might be 13,000 years old. This makes it one of the most ancient life-forms on Earth, and a lot older than the venerable giant redwoods or bristlecone pines.

The contained nature of box huckleberry colonies makes them both wondrous and prone to loss through habitat destruction, which humans seem to have perfected.

The arboretum collection began because Pooler’s now-retired scientific colleague Ruth Dix took a cutting from a stand of box huckleberry that was about to perish in Anne Arundel County. Over the years, she collected and propagated clones from wild colonies in several states, each of them adapted to its own climate, soil and growing environment.

Generally, the plant likes to be in hardwood forests with soils that are sour and dry but not poor. Like a lot of woodland plants in an undisturbed setting, it builds up a symbiotic relationship with beneficial fungi in its root zone.

At the arboretum, the gathering of these different colonies has permitted the cross-fertilization of the flowers and the development of living seed. When I was there, Spaulding was packing the berries in marked vials. In the lab, they will be examined to see which seeds are viable for germination. The clusters of pretty heatherlike flowers, appearing in May, were pollinated by colonies of commercially raised bumblebees brought in for the task.

Each of these assembled plants reflects the peculiar genetic adaptation for its locale, and this diversity of ecotype, as it’s known, bodes well. The aim is to raise strains that can be used to replace lost or threatened colonies in the wild. But through breeding and evaluation, Pooler is also looking to develop traits that nursery growers need in garden plants. These include a willingness to propagate, vigor, disease resistance and ornament of leaf and flower.

In a few years, the box huckleberry may become a stalwart ground cover of the shade garden. One of the hardest challenges for gardeners is to find a reliable evergreen cover for beds in dry shade conditions, a role that used to be filled by the now disfavored English ivy, pachysandra and periwinkle.

One day, perhaps, this wee spreading shrub could be used as a fine-textured foil to blocks of ferns and gingers and hellebores. I dream of the day when I can pop a berry into my mouth.

Read past columns by Higgins at washingtonpost.com/home.

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