The Hackberry is a medium to large deciduous tree with a rounded crown of spreading to slightly drooping branches, growing 50 to 90 feet tall and up to 1.5 feet in diameter.
The bark is smooth, gray or light brown when young, then developing corky warts which in maturity become corky irregular ridges.
Twigs are slender, with a zigzag, light brown to red-brown in color, with lighter lenticels. A true terminal bud is absent on the twig; lateral buds are small, tan, and appressed close to the twig.
The leaves are alternate, 2 to 4 inches long, stalked, and simple, ovate in shape, long pointed, with serrated edges except toward the unequal-sided rounded base. Leaves appear in two rows on the branches. This and the unequal base is a characteristic of the Elm family. Three main veins originate from the base of the leaf, sometimes these veins have hair on the underside. The upper surface is shiny green, sometimes scruffy with fine hair.
Flowers: This species is monoecious, that is, male and female flowers are separate, but on the same plant. Flowers appear in dense hanging clusters from the axils of new leaves, each flower about 1/8 inch wide. The flower calyx has 4 to 5 lobes. Male flowers have stamens that are incurved before flowering, exserted during flowering. Anthers are ovate in shape. The female flower has 4 to 5 nonfunctional stamens (staminodes). The style is short but divided at the top into 2 reflexed lobes.
Seed: Fertile flowers produce a fleshy drupe, 1/4 to 3/8 inch in diameter, that encloses a cream colored stony pit. The outer skin at maturity can be orange-red to dark purple. The fruit is sweet and edible (although Thoreau called it "dry and repulsive") and persists on the tree after leaf-fall.
Habitat: Hackberry prefers rich moist soils of river valleys, upland slopes, bluffs and woodlands, although it is somewhat tolerant of drought, making it valuable as an ornamental street tree. The tree is subject to witches broom gall and nipple gall on the leaves. There is considerable variety within the species.
Names: The common name of Hackberry is thought to be derived from the Scottish 'hagberry' which means 'marsh berry' - applied to a different tree in Scotland but with similar habitat. The genus Celtis is the name of another tree in this plant family and the species occidentalis is used to refer to a New World species to separate it from species of the Elm family in the old world. The author name for the plant classification - 'L.' is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Comparisons: The leaf with unequal sides at the base and the leaves appearing on two rows of the branches are characteristics of the elm family trees. The shape of the leaf, the bark, and the drupe of the Hackberry separate it from the other local elm family trees - Red Elm, Ulmus rubra; Rock Elm, Ulmus thomasii, and American Elm, Ulmus americana L.
Above: A large Hackberry in the Woodland Garden at Eloise Butler. Drawing from North American Sylva, Francois Michaux
Below: 1st photo - Male flower clusters. 2nd photo - Female flower clusters.
Below: Leaves have long pointed tips with serrate edges except near the unequal portion of the rounded leaf base.
Below: 1st photo - The underside can have fine hair on the ribs and veins. Hackberry is subject to the leaf nipple gall as shown here. Note the 3 main veins from the base - typical of the Elm family. 2nd photo - The fruit is a fleshy drupe, 1/4 to 3/8 inch in diameter, that encloses a cream colored stony pit.
Below: 1st photo - Twigs are light brown to red-brown in color, with lighter lenticels. Buds are small, tan and appressed. 2nd & 3rd photos - Example of bark on older trees. The corky warts (2nd photo) that is typical of Hackberry can also be broken into more obvious ridges (3rd photo).
Notes: Hackberry is indigenous to the Garden. Eloise Butler catalogued it on April 29, 1907. Martha Crone also planted it in 1934. Garden Curator Susan Wilkins added additional plants in 2008. Hackberry is found in most Minnesota counties except those of the far north coniferous forest. Its range in North America is from the Rocky Mountains eastward to the coast, including Manitoba, Ontario. P E Island and Quebec in Canada. Absent in Maine and the other Canadian maritime provinces.
Uses: The wood of Hackberry has been used for furniture, boxes, crates and plywood, but it is not a major source for any of that today. Instead Hackberry is mainly used as an ornamental tree. The fruit is consumed by wildlife.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"