In Defense of the Humble Hackberry

I've lost count of the number of times I've heard hackberries casually referred to as "trash trees." The label seems to have stuck, often because of their messy fruit, irregular form or the inconveniences they can cause. Like any species, hackberry has its drawbacks, but its ecological value is often overlooked. It's worth taking a closer look at this much-maligned native tree and what it contributes to our landscapes.

A valuable tree for wildlife

Hackberry (Celtis occidentalis) provides food and habitat for a surprising range of wildlife. Its foliage supports native insects, including the caterpillars of butterflies such as the hackberry emperor, tawny emperor, mourning cloak and question mark. Research by entomologist Doug Tallamy lists 43 species of native caterpillars associated with the hackberry genus (Celtis), highlighting its contribution to the food web.

Its fruit is equally valuable. Common hackberry fruit is eaten by at least 25 species of songbirds, including cedar waxwings, American robins and mockingbirds, as well as wild turkeys, quail and grouse. Squirrels, raccoons and other small mammals also feed on the fruit, which can persist into winter when other food sources become scarce.

Oaks rightly deserve their reputation as ecological powerhouses, supporting an exceptionally diverse range of caterpillars. Hackberry doesn't need to match an oak's numbers to have ecological value. A diverse urban forest needs a variety of native trees, each contributing its own food sources and habitat. Hackberry has a valuable place in that mix.

Hackberry provides food for birds and other wildlife through its fruit, while its foliage supports native insects, including the caterpillars of butterflies such as the hackberry emperor and tawny emperor. Oaks support an exceptionally diverse range of caterpillars and rightly deserve their reputation as ecological powerhouses. But a diverse urban forest needs more than one kind of tree. Different native species support different wildlife, and hackberry has a valuable place in that mix.

Cavities are habitat, too

Mature hackberries often develop cavities and hollows that provide shelter and nesting opportunities for wildlife. Woodpeckers may excavate cavities in suitable wood, and other birds and animals can use them later. In urban landscapes, where mature trees and natural habitat features are increasingly scarce, these cavities can be an important resource.

Of course, cavities and decay can also affect a tree's structural integrity. Their presence requires appropriate assessment, not automatic removal or automatic retention. As arborists, we need to consider both the structural implications and the ecological benefits. A cavity can be a structural concern and an ecological asset at the same time.

Yes, hackberries have their shortcomings

The Asian woolly hackberry aphid is a genuine nuisance in Tennessee. During heavy infestations, it produces honeydew that coats cars, patios and other surfaces, often followed by black sooty mold. Hackberries can also develop poor branch architecture and structural defects, making appropriate species selection and pruning important.

These are legitimate considerations, particularly when choosing a tree for a specific site. A hackberry planted above a frequently used parking space may not be ideal. But a drawback in one setting doesn't make an entire species worthless.

Every tree has its shortcomings. Oaks drop acorns and leaves, sweetgums produce spiky seed balls, maples can develop structural problems and girdling roots, and Osage oranges have formidable thorns. Yet we don't write off these species entirely because of their inconveniences. We recognise their individual characteristics, understand their limitations and plant them where they're appropriate. So why should hackberry be any different?

The goal isn't to find a perfect tree. It's to understand the trees we have, select appropriate species for the site and recognise the value each brings to our urban forest. A tree's inconveniences don't erase its ecological value.

The value of a mature tree

A mature tree provides benefits that cannot be replaced overnight. Its canopy, woody structure and established habitat take decades to develop. Where a mature hackberry is suitable for its surroundings and can be retained with an acceptable level of risk, preserving it can maintain ecological value that a newly planted tree cannot immediately replace.

Sometimes removal is necessary, and no tree should be retained at the expense of public safety. But when a mature tree is dismissed simply because of its reputation, it's worth asking whether we're making an informed assessment or repeating a popular opinion.

The right tree in the right place

I'm not suggesting hackberries should replace oaks or that they're suitable for every landscape. Tree selection should account for available space, soil conditions, infrastructure, intended use and long-term management. Oaks are exceptional native trees, but so are other species in their own ways. A diverse urban forest benefits from a range of trees suited to their surroundings.

Hackberry isn't a perfect tree, but no tree is. It provides food for wildlife, supports native insects, tolerates challenging urban conditions and, as it matures, can develop cavities that offer valuable habitat.

The next time a hackberry is dismissed as a "trash tree," perhaps we should look a little closer. Its value extends well beyond its appearance or the mess it might make. Sometimes, the humble hackberry deserves a little more respect.

Nashville Trees and Gardens