Underutilized Trees for Urban Use: Carolina Silverbell

Carolina silverbell (Halesia carolina) flowers. Photo from MOBOT Plant Finder (missouribotanicalgarden.org/PlantFinder)

Carolina silverbell (Halesia carolina) produces fruits that look more like winged footballs than bells. Thus, one taxonomic synonym for this tree is Halesia tetraptera, where tetraptera means “four wings.” Carolina silverbell falls in that category of urban trees that are best used in parks, campuses, generously wide tree lawns, and other places where the influence of the built environment (asphalt, concrete) on the soil pH is not too profound. This is because it can’t tolerate highly alkaline soil and indeed prefers acidic soil where possible. In high pH-soils, its leaves can appear chlorotic (yellowed).

Carolina silverbell fruits start out yellow, then turn rusty brown. Photo by Michelle Sutton

Other than an affinity for a slightly alkaline, neutral, or acidic soil, Carolina silverbell is quite soils-adaptable, including being able to withstand occasionally wet soils. In its native range (primarily the southeast U.S.), it grows as an understory tree, which tells you it can tolerate part shade; it does fine in full sun if it’s watered during a prolonged drought. Like most trees, it doesn’t thrive on soil compaction.

Mature Carolina silverbell growing in favorable conditions. Whereas normally mature trees of this species are pyramidal in shape, this one is tall and slender, probably due to decades of competing with neighbors for light. Photo by Michelle Sutton

Depending on the source, Carolina silverbell is cold hardy down to Zone 4 or to Zone 5. It has no serious insect or disease susceptibilities, but it does not care for deicing-salt spray (another reason to keep it away from asphalt and concrete). It’s said to be tolerant of proximity to black walnut trees.

Halesia carolina foliage Photo by Michelle Sutton

As an understory tree it tends to max out at 25-35 feet tall, but an open-grown specimen can get considerably taller. (See photo above of a majestic mature one on the Vassar College campus in Poughkeepsie that is 50-plus feet tall.) The showy white, bell-shaped flowers emerge in downward-pointing clusters in May, from the previous year’s wood.

Bark of mature Carolina silverbell. Photo by Michelle Sutton
Bark of young Carolina silverbell. Photo by Michelle Sutton

Carolina silverbell is worthy of the careful siting it requires because it has so many worthy ornamental traits in addition to the flowers: a pleasing medium-dark green foliage, showy aforementioned fruits (starting out pale yellow, then turning football-brown), attractive yellow fall color, and distinctive and handsome bark. A pink-following cultivar called ‘Arnold Pink’ can be found in the trade.

‘Arnold Pink’ Carolina silverbell. Photo from Moon Nurseries (moonnurseries.com)

Carolina silverbell is often confused with its cousin, Japanese silverbell (Styrax japonicus); they are both in the Styracaceae family. We’ll cover that species here soon.

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