December 2022 - Hackberry
Common Name: Common hackberry; also called Hackberry, American Hackberry, Nettle Tree, beaverwood, and false elm.
Botanical Name: Celtis occidentalis
Native Range: Native to New Jersey and throughout central and northeastern North America, in USDA Hardiness Zones 3 to 9. Grows best in bottomlands along rivers and streams, common on slopes and bluffs, and in fence rows. In New Jersey, it is mainly a tree of the piedmont.
Height: Its mature size varies, depending on its location. Its typical mature height is 40 to 60 feet, but it can grow to 100 feet in ideal conditions.
Spread: Crown is 40 to 60 feet wide in ideal conditions.
Form: A medium to large deciduous tree whose form varies in response to its habitat. In youth, it is weakly pyramidal. Grown in the open, it matures to a vase shape, with a straight trunk, 1 to 3 feet in diameter, and a rounded or oval crown with stout spreading and arching branches.
Growth Rate: Medium to fast growth rate, to 20 to 30 feet over a 10 to 15-year period under ideal conditions.
Sun: Prefers full sun but will tolerate part shade.
Soil: Best grown in moist, organically rich, well-drained soils, but will tolerate a wide range of soil conditions, including wet soil, dry soil, clay soil, and poor soils.
Leaf Description: Alternate, simple, ovate to oblong-ovate, bright green leaves (2-5” long) with acuminate (sharply pointed) tips and mostly uneven leaf bases. Coarsely toothed from mid-leaf, attached via ½ to ¾ inch petiole. The upper side is often rough-textured, underside paler.
Fall Color: Pale yellow. Flower Description: Insignificant green flowers, 1/8 inch wide, on drooping stalks appear from April to May. Male and female flowers are borne separately on the same tree, although sometimes perfect flowers (with both male and female parts) are also present. Male flowers are in clusters near the base of new branchlets and female flowers are solitary or in pairs in leaf axils.
Fruit: Female flowers give way to an often-abundant crop of round fleshy berry-like drupes, 1/3 inch in diameter, ripening from green to orange-red to deep purple. Each drupe has tough skin, a thin pulp layer, and one hard round brown seed within. The pulp layer is edible and somewhat sweet.
Bark Description: Smooth and cool gray. Distinctive narrow corky projecting ridges and furrows form on the trunk and older limbs as the tree matures, providing multi-season interest.
Wildlife Benefit: Hackberries are among the best food and shelter trees for wildlife. Many birds, including quail, pheasants, woodpeckers, and cedar waxwings, consume sweetish fruits, which are high in protein. They are an important winter food source for birds. It is also a larval host plant for many butterflies, including the American snout, question mark, mourning cloak, and hackberry emperor.
Tolerates: Hackberry is a tough, adaptable tree. It is tolerant of moderately wet to dry conditions. Though its leaves may wilt under sustained drought, it will recover quickly once watered. It tolerates both sandy and clay soils, even rocky soils. It withstands both acid and alkaline conditions. It tolerates wind and urban pollutants. This versatility makes it a worthy candidate for enduring the vicissitudes of climate change.
Possible Disease and Insect Problems: Hackberry thrives without pampering. It is considered to be essentially pest-free. Nonetheless, it can have powdery mildew, as well as leaf spots, root rot, lace bugs, and scale.
Uses: As a tough shade tree, it is a good choice for parks and other large open areas, parking lots, and naturalized sites. Its arching branch structure makes it appropriate for use as a street tree. Its tolerance of windy conditions makes it a good appropriate for use in a windbreak.
Where to be found on municipal property:
• Hackberries are on Walnut Lane across the street from the Princeton Middle School.
• Hackberry are located at the cross street of Aiken Avenue and Murray Place, on Aiken.
• There is a Hackberry in Marquand Park along the walking trail across from Willow Oak.
• Due to its tolerance of urban conditions, Hackberry will be one of the trees planted in the Witherspoon Street corridor.
• Mites and fungi can induce the formation of “witches’ brooms” (dwarfed, dense, contorted twig clusters) on the tips of hackberry branches. These can degrade the appearance of the tree, particularly in winter. Resistant cultivars are available.
• Hackberry leaves support the life cycle of numerous gall-producing insects. As a result, nipple galls may riddle leaf surfaces. While this is ecologically beneficial and not harmful to the health of the tree, many consider this disfiguring. Gall-resistant hackberry cultivars are available and planting sites can be chosen where the leaves will not be too closely observed.
• The cultivar ‘Prairie Sentinel’ has a columnar form that lets it fit into a site that is too narrow for a full-width tree.
The American Horticultural Society, Trees, Ortho Books, 1982.
Dirr, Michael A., Manual of Woody Landscape Plants, Their Identification, Ornamental Characteristics, Culture, Propagation and Uses, 5th Edition, Stipes Publishing L.L.C., 1998, pp. 201-202.
Kartesz, J.T., The Biota of North America Program (BONAP). 2015. North American Plant Atlas. (http://bonap.net/napa). Chapel Hill, N.C. http://bonap.net/MapGallery/County/Celtis%20occidentalis.png
Kershner, Bruce et al., Field Guide to Trees of North America, National Wildlife Federation, Sterling Publishing Co., 2008, p. 364.
Lady Bird Johnson Wildflower Center
Martine, Christopher, Trees of New Jersey and the Mid-Atlantic States, Forest Education Resource Center, NJ Department of Environmental Protection, 4th Edition, 2000, p. 52.
Michelle Sutton, City Trees Editor, “Announcing the 2020 SMA Urban Tree of the Year: Hackberry (Celtis occidentalis)”
Missouri Botanical Garden
RPD No. 662 - Witches' Broom of Hackberry, Integrated Pest Management, University of Illinois at Urbana-Champaign