Description and Habitat
The Long Point Region has among the most biodiverse floral assemblage in Canada, including many southern vegetation communities. One of these southern tree species is the Common Hackberry (Celtis occidentalis), a large tree primarily of floodplains in the hemp family (Cannabaceae). There are two species of Hackberry in Ontario, the other species is a shrub (Celtis tenuifolia), found only near the Pinery Provincial Park, Point Pelee National Park, and Pelee Island. In contrast, natural populations of Common Hackberry are widely observed across Ontario’s Lake Erie Region (Carolinian Life Zone), from Grand Bend to Hamilton and southwards, though specimens have been planted north of Hackberry’s original distribution. However, Common Hackberry reaches it’s highest abundance on Pelee Island and Point Pelee National Park, where it is the dominant tree. It is distributed southwards into Tennessee, and west to Nebraska. In the southeastern United States, Common Hackberry is replaced by Sugarberry (Celtis laevigata) to the south, another tree species that shares the same habitat preferences.
Common Hackberry is distinguished from other tree species to by it’s bark, which is comprised of corky ridges, creating irregular patterns. Hackberry leaves are ovate, broader at the base than at the tip, 5-12 cm long. The leaf margins are serrated (toothed). In the autumn, Hackberry foliage turns light yellow. Hackberry flowers in May, with the seeds ripening in September, promptly consumed by birds. The fruit is a fleshy drupe, each with a single seeds, measuring around 0.5 to 1 cm long.
Common Hackberry prefers riparian forests, although it can adaptable in other ecosystems. In riparian settings it most often grows with Black Walnut (Juglans nigra), Green Ash (Fraxinus pennsylvanica), Burr Oak (Quercus macrocarpa), Basswood (Tilia americana), and Shagbark Hickory (Carya ovata). It can also grow in more shaded, late-successional environments with Black Maple (Acer nigrum), Bitternut Hickory (Carya cordiformis), and Blue Ash (Fraxinus quadrangulata), provided that there are forest gaps to support it’s regeneration, since Hackberry is only moderately tolerant of shade. The understories of Hackberry forests are usually comprised of a very diverse set of shrubs, and wildflowers, including Bladdernut (Staphylea trifolia), Blue-beech (Carpinus caroliniana), Dogwoods (Cornus sp.), and Chokecherries (Prunus virginiana).
Wildlife importance
Hackberries are consumed by a wide variety of birds and small mammals. Since Pelee National Park and Pelee Island are migrant traps (hosting a large number of birds each year), this likely supported Hackberry’s proliferation in those areas. The foliage is a food source for a large number of butterfly and moth caterpillars, including Hackberry Emperor Butterflies (Asterocampa celtis), which are host specific to the Hackberry (Celtis) genus. Other insects utilizing Hackberry include the Tawny Emperor (Asterocampa clyton), Question Mark Butterfly (Polygonia interrogationis), Mourning Cloak Butterfly (Nymphalis antiopa), American Snout Butterfly (Libytheana carinenta), and Eastern Comma Butterfly Comma (Polygonia comma), White-marked Tussock Moth (Orgyia leucostigma), Banded Tussock Moth (Halysidota tessellaris), and Io Moth (Automeris io).
Fun facts
- The small, dark hackberries persist on the tree well into winter, even into early spring. They are important food source for many frugivorous bird species during the colder months, when other food sources are scarce.
- Hackberry was placed in the Elm family (Ulmaceae) for decades, which the Hemp Family (Cannabaceae) is closely related to, within a larger group called the urticalean rosids, or Nettles. Hackberries and elms have a similar leaf morphology, habitat preference, and growth form.
- The dense branching and rough bark of the hackberry provide excellent structure and camouflage for nesting songbirds.
- Though Hackberries rely on wildlife for seed dispersal, the flowers are wind-pollinated like most of Ontario’s other canopy trees.
Written by Matthew Palarchio, HBSc in Environmental Sciences, Western University.
Photos by Matthew Palarchio
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