In the Garden: Unfair Competition
By Charles Kidder
Competition is said to improve the breed. A plant that has to duke it out with other plants for resources should end up better for it, right? Or at least the best of its offspring should prevail over the weaker ones. But what about competition in another sense, where one competitor barely gets an invitation to the contest?
The leading contender in the fray of spring-flowering trees is arguably the familiar flowering dogwood (Cornus florida). Abundant in the wild as well as ubiquitous in gardens, who would dare challenge the dogwood? So, the shy, retiring silverbell tree (Halesia spp.) just sits in the corner and hopes somebody will notice it. And perhaps even invite it into their gardens.
As yet another tree with white flowers in mid-to-late April, silverbells have an uphill battle to gain attention. But not all white flowers are created equal. The “bells”, only ½’’ to ¾” long, are white and hang delicately from the branches. What they lack in size, they make up for in numbers, cloaking the tree before and during leaf emergence. Attractive from any angle, they show best when viewed from below, allowing you to look up into the bells. A good choice for a patio, where folks can sit under the tree, or on a hillside where you can stroll under it.
In their native haunts, silverbells can be relatively common trees, but unfortunately we’re beyond where they grow wild. One species of Halesia is found in China, with the rest growing in the southeastern United States. Just how many species are native to the U.S., and what they’re properly called, gets a bit murky. As gardeners, the distinctions aren’t that significant, since all three species are pretty similar. They are typically fairly small understory trees, often with two or three trunks with subtle striping. The simple, undivided leaves may turn soft yellow in the fall, but silverbells aren’t known for spectacular autumn color.
The Little Silverbell, H. carolina, has the smallest flowers and grows in alluvial forests of the deep south. The Common, or Mountain, Silverbell (H. tetraptera) is the most widespread, ranging from one or two counties in Southwest Virginia all the way to Texas and Oklahoma. The center of its distribution is the southern Appalachians, especially the Great Smoky Mountains, and this is where the taxonomy becomes confusing. Most Common Silverbells are small trees, ranging up to about thirty feet tall. But in the mountains, silverbells can reach heights of eighty feet, with a two-foot diameter. These trees also have slightly larger flowers; sometimes labeled as a separate species, they’re now more commonly regarded as a variety.
The Two-wing Silverbell (H. diptera) is slightly more distinct from its brethren, but only because its fruits have two wings rather than four. There is also a variety of this deep south species, magniflora, but the “large” flowers are still just barely over an inch in length. Some authorities consider this variety to be more drought-tolerant, however.
And speaking of drought, what growing conditions should you provide for your silverbell? In the wild they generally receive abundant moisture, either growing near streams, in moist mountain coves, or along wet slopes. So don’t plant them in a hot, dry, exposed place, and be prepared to provide some supplemental water in dry spells. Partial shade, with protection from the hottest sun, will provide the best conditions for flowering and good growth. Mulch to keep the roots cool. One blessing: grown in the right conditions, silverbells are generally quite pest- and disease-resistant.
Silverbells are not widely available, but with some looking or travelling, you should be able to find one. There are a few cultivars out there; most focus on pink flowers, although there is one weeper, as well as a variegated selection. One caveat when buying the pink varieties: if possible, look at the actual tree, since the degree of pinkness is highly variable.
Even if you don’t plant a silverbell, take a trip to find them. For years a silverbell has grown in the gardens behind Pavilion III at UVA. I hope it’s still there, but haven’t checked recently. If you’re up for a drive, head down to the Smokies and look for the really big examples. One of my favorite hikes is up into Albright Grove on the Tennessee side of the mountains. Among many large trees of various species, mature silverbells stand out. Instead of the striped bark of young specimens, they develop gray-black-brown plates that are almost iridescent, well worth the hike.
And what about snowbell trees, cousins to the silverbells? Perhaps another contender in this competition? Stay tuned.