Common Hackberry or American Hackberry

(Ulmaceae - Elm Family)

Form

• large shade tree
• usually maturing at about 70' tall by 50' wide, but with the capacity to grow much larger
• upright oval growth habit in youth, quickly losing its central leader and becoming rounded to irregular in growth habit with age
• rapid growth rate

Culture

• full sun (tolerant of partial sun in youth)
• prefers moist, rich soils but is highly adaptable to many adverse conditions, including wet soils, dry soils, poor soils, compacted soils, rocky soils, soils of various pH, heat, drought, flooding, pollution, and windswept areas
• species form is propagated primarily by seed, while stem cuttings from cultivars may be grafted onto seedling understock, or they may be rooted
• Elm Family, with several cosmetic disease (leaf spots, leaf nipple gall), pest (scale), combination (witches' broom), and physiological (leaf chlorosis) problems, none of which seem to significantly slow the species down, and not including Dutch Elm disease, which is restricted to members of the genus Ulmus
• moderate availability, usually in ball and burlap form
• often a volunteer tree in very wet or very dry sites, waste sites, fence rows, and cut-over woodlots, which is left because of its convenient quick shade or windbreak function (or it rapidly becomes too big to conveniently cut down)
• Common Hackberry is somewhat sensitive to being transplanted in Autumn, and care should be taken to amend the soil, fertilize, water thoroughly, mulch adequately, and avoid Winter salt spray, to enhance survival chances during the first Winter

Foliage

• alternate along the stem, medium to dark green, and about 4" long
• leaves are ovate, serrated, with an acute to acuminate apex, and with the leaf base asymmetrical (skewed or lop-sided, like the foliage of most Elm Family members)
• leaf spots and/or nipple gall on Summer and Autumn foliage are cosmetic leaf diseases
• chlorotic (yellowing) foliage in Summer is usually indicative of alkaline (high pH) soils that result in manganese nutrient deficiency to the tree
• fall color is chartruese to green an ornamentally poor

Flowers

• greenish-yellow in April and May, a mixture of staminate, pistillate, and perfect flowers on the same tree (polygamo-monoecious), giving a fine texture and lime color to the tree in early Spring as the foliage just begins to emerge

Fruits

• greenish small round fruits hang from the leaf axils, changing to an ornamentally insignificant orange or purple color at maturity in September and October, either abscising to the ground or devoured by the birds

Twigs

• light gray, slightly zig-zag, and irregular in their growth pattern
• twigs have no terminal buds and are often knobby
• witches' broom occasionally affects this species, being a dense clustering of miniature stems and foliage scattered throughout the newer growth of the tree, caused by the combined effects of a mite (pest) and a fungus (disease)
• the branching pattern of the species form of this tree rarely goes very far in a straight line, constantly forking, curving, dipping, and ascending

Trunk

• light gray, similar to Beech (Fagus) in color, but not smooth
• very corky to warty ornamental bark, slowly becoming platy with age
• often to 3' or more in diameter on mature trees, losing the central leader in youth and eventually with significant basal flare as the trunk meets the surfacing roots near the base of the tree
• wood is not storm-prone, being much stronger than Silver Maple (Acer saccharinum, another large tree that is highly adaptable to poor soils of wet or dry character, and which is often overplanted as a quick shade tree)

ID Summary

• ovate leaves with asymmetrical bases occur in alternate fashion along somewhat zig-zag, knobby twigs, with the gray branches and massive trunk developing a warty character with age
• inflorescences are small and lime-green in Spring, giving rise to small round fruits in Autumn which are devoured by the birds
• leaves often have spots on the upper surface and nipple gall on the lower surface, trunk develops basal flare with age, and stems may develop witch's broom throughout the canopy

USAGE

Function

• shade tree (often as a native tree at property borders and neglected sites, where it was once a pioneer invader tree), deciduous windbreak, or tree for erosion control

Texture

• medium texture overall in foliage and when bare (fine-textured twigs are contrasted by the bold trunk and irregular branching pattern); truly a difficult tree in the species form to classify in terms of its non-uniform texture
• average density in foliage but thick density when bare

Assets

• very urban tolerant
• rapid growth and establishment (for shade, windbreak, or erosion control)
• ornamental bark with age
• very cold-hardy

Liabilities

• gets too large for most urban areas (in canopy height and width, trunk girth, and basal trunk flare)
• foliage (leaf spot, nipple gall, chlorosis) and twig (witches' broom) cosmetic diseases are sometimes present
• bird droppings are often found underneath the tree in early Autumn due to the bird's overconsumption of the ripened fruits
• poor fall color

Habitat

• zones 2 to 9
• native to floodplains of the Eastern United States

SELECTIONS

Alternates

• large shade trees for stressful sites where poor environmental conditions exist (Ailanthus altissima, Fraxinus americana, Gleditsia triacanthos inermis, Morus rubra, Ulmus parvifolia, etc.)
• large shade trees with ornamental bark (Betula nigra, Fagus sylvatica, Fraxinus americana, Gleditsia triacanthos inermis, Ulmus parvifolia, etc.)

Variants

• Celtis occidentalis 'Chicagoland' - maintains a single, relatively straight trunk throughout most of its life
• Celtis occidentalis 'Prairie Pride' - possesses a uniformly oval canopy, lustrous dark green thick foliage, stems that do not develop witches' broom, and low fruit set

NOTES Translation

• Celtis is the Greek name for the Hackberry tree (Hackberry itself is a derivative of the Scottish name Hagberry, which is actually a type of Cherry).
• occidentalis translates as "western", referring to the American continent where it is native.

Purpose

• Common Hackberry is one of the most urban-tolerant and rapidly growing shade trees.

Summary

• Celtis occidentalis is a tough and very large tree, growing rapidly to provide shade, deciduous windbreak, and/or erosion control under many different types of stressful conditions.