Hackberry trees are worth another look

Day by day, hour by hour, trees are dropping their leaves, allowing us to appreciate their architectural structure. While growing conditions can shape a tree’s form – a white oak’s limbs will be truncated in a crowded forest, but in the middle of a pasture, they’ll sprawl – each species also has its own inherent traits. Compare the lateral limbs of a black gum with a vase-shaped willow oak.

Some sources compare the shape of the common hackberry (Celtis occidentalis) to one of our most graceful trees, the elm. In my experience, this is yet another reminder that you can’t believe everything you read on the internet.  At its best, the hackberry has a great deal of character. According to the Lady Bird Johnson Wildflower Center, the “broad crown is often erratic in shape.” Hackberries often grow in riparian areas. Amid the dense vegetation, they branch frantically, desperate for any shaft of sunlight. Even in the open, they can’t seem to resist sending out awkward limbs. These are prone to break. They also tend to produce unsightly sprays of twigs known as witches’ broom.

Hackberry leaves covered in sooty mold. Photo: Ruth Ann Grissom

The hackberry’s trunk resembles a beech with a bad case of acne. The smooth bark is covered with what is often described as “corky warts.” Toward the base, these bumps seem to coalesce into deeply grooved ridges. Their leaves have no appreciable fall color, and they’re susceptible to powdery mildew and hackberry nipple gall. Even worse, they’re often attacked by the Asian woolly hackberry aphid. These fluffy insects, resembling whiteflies, secrete a sticky honeydew. This, in turn, creates conditions for a proliferation of sooty mold. Anything unfortunate enough to inhabit the area under a hackberry’s canopy — a lawn, an herbaceous layer, a sidewalk, roof or deck — is stained dark gray.  While the tree itself doesn’t seem to suffer, a poorly sited hackberry might force homeowners to apply systemic pesticides, which kills beneficial insects as well as the woolly aphid.

Despite these negatives, the Arbor Day Foundation actually encourages their use as a street tree or shade tree. (Perhaps this advice pre-dates the woolly aphid invasion in the 1990s.) While hackberries tolerate many challenging conditions – air pollution, heavy clay, wet soil or drought – it’s hard to imagine why someone would actually want or need to plant one.  In the Piedmont, they routinely pop up in the neglected margins of suburban yards. 

That’s where I first encountered a hackberry. On a fine autumn day many years ago, I noticed our late, great Jack Russell terrier, Buster, grubbing around in the leaves along our property line. There, I’d left a moonvine entwined in the fence. Past its prime, it was still adorned with clusters of shiny purple seed pods. I suddenly remembered that moonvine seeds were hallucinogenic!  Alarmed, I fell to my knees and crawled alongside Buster, trying to determine exactly what he was eating.  To my relief, it wasn’t the seeds at all, but small brownish-purple, slightly wrinkled fruits. I traced their source to the limb of a neighbor’s scraggly tree that reached into our yard. Animal Poison Control assured me hackberry fruits aren’t toxic.  In fact, the flesh is said to be sweet, with a flavor reminiscent of dates. Buster certainly had a taste for them, but I’ve never worked up the courage to try them myself.

I might recoil at thought of having a hackberry in my backyard, but I celebrate them in the Piedmont’s natural areas. In the right setting, they’re supremely beneficial to wildlife. Their fruits might lack the aesthetic appeal of holly berries, but they’re prized by birds in winter, especially woodpeckers, waxwings, mockingbirds and robins. The hackberry is also a host plant for several butterfly species including the American snout, mourning cloak, question mark, hackberry emperor and tawny emperor.

Hackberries remind me of the French term jolie laide (literally “beautiful ugly”). It’s used to describe someone who’s unconventionally attractive. Critic Daphne Merkin defines it as “a triumph of personality over physiognomy, the imposition of substance over surface.” Two centuries ago, renowned French botanist Andre Michaux recognized the hackberry’s allure. In The North American Sylva, he wrote, “The Hack Berry is certainly one of the most beautiful trees of its genus.” He went on to say, “In France, it is principally esteemed for the rapidity of its growth; and it is to be wished that its wood may be found valuable enough to entitle it to a place in our forests.”