Silverbells

Silverbells: It's Christmastime in the Cove Forests

So much is happening in April that it is hard to concentrate on just one plant or animal or mushroom. The forest is greening from the bottom up as spring ephemerals emerge for a few short weeks of light before the trees intercept most of it. Red efts cruise the leafy forest floor that produces such delicacies as ramps and morels, while ruby-throated hummingbirds and magnificently colored warblers flit through the trees overhead.

The trees visited by those warblers are just beginning to leaf out. As the leaves unfurl, hungry caterpillars nibble on the fresh greenery, but are themselves hors-d’oeuvres for the birds. Leaves, caterpillars, and migratory birds all appear in these mountains within a few short days of each other, for each depends on the other.

Leaves first appear on the trees of the cove forests. Appalachian cove forests are ecological communities of plants, animals, and other organisms, and this particular community has the highest diversity of tree species outside of the tropics. About 30 different species of trees and 1500 different herbaceous plants occur in this community, and these are all right in our backyard of the southern Appalachians. These coves are rich in both moisture and nutrients, and the deciduous trees contribute to the formation of the topsoil with their yearly addition of leaves to be decomposed. Topsoil in these rich coves can be 6 feet in depth and loamy black. Even the soil and trees are connected to each other through a reciprocal relationship.

One of the more common trees in the Appalachian cove forest is Carolina silverbell, named for the pendant white bells that hang from its branches in bunches. The bells are about an inch long and are composed of four white petals that are fused together around a cluster of stamens, laden with yellow pollen, and a central stigma. When they fall, it looks like snow covering the ground, more like Christmastime than springtime. In fact, the presence of silverbell (and white basswood) identifies the cove forest natural community, because these trees only occur in the Appalachian cove forest. Tulip trees (yellow poplar), dogwood, and Fraser magnolia are also common but are not unique to this community.

By far the most common of three species, the Carolina silverbell, Halesia tetraptera, is found in the cove forests of the southern Appalachians. Its scientific name refers to the four (tetra) wings (ptera) of the oblong, 1-2 inch fruits. Silverbells are usually understory trees but can reach into the canopy. They grow to a maximum height of about 70 feet, but are usually much smaller. Tulip trees in these same coves reach 150 feet or more. The twigs and small branches of Carolina silverbell have distinctive white streaks on them, and the bark of larger trees is blocky.

There are two other species of Halesia in the USA, both uncommon and both occurring in moist habitats along the Gulf Coast and into South Carolina. A fourth species occurs in China. One of these southeastern species, little silverbell, is named Halesia carolina because it is the species that was initially discovered.

Get out this spring for a hike through an Appalachian cove forest. Any rich cove in the southern Appalachians is likely to harbor this community, but the presence of Carolina Silverbell confirms it. Not only are the Silverbells beautiful, but the birds, salamanders, wildflowers and other trees are as diverse as anywhere in the USA.

PHOTO: The pendant flowers of Carolina silverbell.

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