// SPECIES PROFILE · TREE · NATIVE · WILDLIFE KEYSTONE · URBAN-TOUGH

Common Hackberry

Celtis occidentalis

Common hackberry is a medium to large tree 40–60 ft tall with distinctive corky, warty bark and elm-like leaves that turn a muted, buttery yellow in fall. It produces small, sweet, date-like orange-brown drupes that hang on bare branches deep into winter — a critical cold-weather food for cedar waxwings, robins, and over two dozen bird species. The hackberry is the larval host for at least five butterfly species including the hackberry emperor, tawny emperor, and question mark. Celtis occidentalis is found in bottomlands, fencerows, and upland woods across all of NE Oklahoma, and it is exceptionally tolerant of urban conditions, clay soils, and drought — one of the most resilient and ecologically valuable native shade trees available for the Tulsa landscape.

// QUICK FACTS

Family: Cannabaceae (hemp family; formerly Ulmaceae — elm family)
Life cycle: Deciduous perennial tree; moderately long-lived (100–150+ years in favorable sites)
Native range: Eastern and central North America — southern Canada to Georgia, west to the Great Plains including all of OK
USDA hardiness: Zones 2–9 (Tulsa = 7a/7b — very hardy)
Mature size: 40–60 ft tall, 30–50 ft spread; occasionally to 100 ft on exceptional sites
Bloom: April – May (NE OK); wind-pollinated, inconspicuous
Flower: Inconspicuous, greenish-yellow, in small clusters at leaf bases; male and female/perfect flowers on same tree (polygamo-monoecious)
Fruit: Small, spherical drupe ⅓–½ in; orange-brown to dark purple; thin sweet flesh, single hard seed; ripens September–October, persistent into winter
Sun: Full sun to partial shade; best form in full sun
Soil: Extremely adaptable — clay, loam, sand, compacted urban fill; pH 5.5–8.0; tolerates occasional flooding and significant drought
Water: Low to medium; drought-tolerant once established; tolerant of periodic inundation
Wildlife: Winter fruit for 25+ bird species · larval host for 5+ butterfly species · pollinator-support · cavity-nesting habitat
Conservation: G5 — Secure; abundant and widespread throughout native range

Common Hackberry (Celtis occidentalis) — mature tree with corky, warty bark and elm-like leaves — *Celtis occidentalis* — the wildlife keystone hackberry: corky warty bark, small sweet drupes, and host to five butterfly species. Photo: Rooted Revival.

Identification

[ field key — habit · bark · leaf · flower · fruit · distinguishing features ]

Habit, Bark & Form

A medium to large deciduous tree 40–60 ft tall with a broad, rounded to somewhat irregular crown and often a short, thick trunk that divides into several large ascending branches. The bark is the tree's most distinctive feature: gray to light brown, smooth on young trees, but soon developing conspicuous corky ridges, warts, and knobs that form a unique, rough-textured pattern — once learned, hackberry bark is unmistakable at any distance. On very old trunks, the bark becomes deeply furrowed and somewhat scaly. The overall form tends to be more open and "stiffer" than the graceful, vase-shaped American elm, and the tree's silhouette in winter is recognizable by its twiggy, somewhat chaotic branching pattern and the small, witches'-broom-like clusters of twig growth that often form at branch tips.

Leaves

Leaves are simple, alternate, ovate to broadly lance-shaped, 2–5 in long and 1–3 in wide, with a strongly asymmetrical (oblique) base — one side of the leaf base is noticeably larger and attaches lower on the petiole than the other, a trait shared with elm leaves. The margins are sharply serrated, especially from the midpoint to the tip, and the leaf tip is long-acuminate (drawn out to a narrow point). The upper surface is rough and sandpapery to the touch (scabrous); the underside is paler and hairy along the veins. Fall color is a soft buttery yellow — not spectacular compared to maples or black tupelo, but pleasant in the landscape. The rough upper leaf surface is a good way to distinguish hackberry from slippery elm (which has consistently rough leaves) vs. American elm (smooth upper surface).

Flowers & Pollination

Hackberry flowers are inconspicuous and easy to overlook — small, greenish-yellow blossoms borne in the leaf axils in April–May, appearing as the leaves are expanding. The tree is polygamo-monoecious: it carries both male (staminate) and female/perfect flowers on the same tree, often in the same cluster. Pollination is by wind, and a single tree can set fruit without a partner, though cross-pollination improves fruit set. The flowers lack showy petals, and the entire blooming event is subtle enough that most people never notice it — the fruit, not the flower, is how hackberry announces itself.

Fruit & Distinguishing Features

The fruit is a small, spherical drupe ⅓–½ in in diameter, borne on a slender stalk (pedicel) ½–1 in long. In fall (September–October), the drupes turn orange-brown to dark reddish-purple and the thin, sweet flesh surrounds a single large, hard, stony seed. The flavor is mildly sweet and pleasant, reminiscent of a date or a raisin with a hint of molasses. The fruit persists on the tree well into winter — you will see hackberry trees in December and January with bare branches studded with dark drupes, an instantly recognizable winter silhouette. Key distinguishing features: the unique corky/warty bark; the asymmetrical leaf base combined with a rough-sandpapery upper surface; and the tiny, date-like, persistent winter fruits.

Habitat & Range in NE Oklahoma

Celtis occidentalis has one of the widest distributions and broadest habitat tolerances of any North American tree, ranging from southern Canada to the Gulf Coast. It is common throughout Oklahoma, and in the northeast part of the state it occurs in bottomland hardwood forests, floodplain terraces, fencerows, upland woods, limestone glades, and urban/suburban landscapes in essentially every county. You will find hackberry growing alongside pecan, sycamore, and black willow in the Arkansas River bottomlands; mixed with post oak and blackjack oak in the drier uplands of the Cross Timbers; and as a volunteer tree in alleys, vacant lots, and neglected corners throughout the city of Tulsa.

Hackberry's ecological flexibility is extreme: it tolerates seasonal flooding in river bottoms and prolonged drought on rocky ridge tops. It grows in soils ranging from deep alluvial silt to heavy, compacted urban clay. It recovers from being partially blown over in windstorms and resprouts vigorously when cut. This is not a fussy tree that requires careful site selection — it is a tree that you plant because it will thrive in the difficult spot where nothing else grows well: the hot, compacted parking lot island, the clay-heavy suburban yard, the degraded fencerow, the low corner of a property that floods briefly after every heavy spring rain.

Ecology & Wildlife Value

[ winter bird fruit · Lepidoptera hosts galore · cavity nesting · urban wildlife ecology ]

Winter Fruit: Birds & Mammals

Hackberry fruit is one of the most important winter wildlife foods in eastern North America. Because the drupes persist on the tree from October through February (and sometimes into March), they provide a reliable food source during the leanest months of the year when virtually all other fruits and insects are gone. The list of bird species that depend on hackberry fruit includes cedar waxwings, American robins, Northern mockingbirds, Eastern bluebirds, yellow-rumped warblers, hermit thrushes, Northern flickers, red-bellied woodpeckers, starlings, blue jays, and wild turkeys. Over two dozen documented bird species consume the fruit. Mammals including raccoons, opossums, squirrels, foxes, and white-tailed deer also feed on fallen hackberries. The fruit is calorie-dense for its size, with a relatively high fat content (from the seed) compared to many other small fruits.

Lepidoptera Hosts

Hackberry is one of the most important Lepidoptera host trees in North America. It is the larval food plant for at least five butterfly species that are entirely or largely restricted to Celtis: the hackberry emperor (Asterocampa celtis), the tawny emperor (A. clyton), the question mark (Polygonia interrogationis), the mourning cloak (Nymphalis antiopa), and the American snout (Libytheana carinenta). The hackberry emperor, in particular, is rarely found far from its host tree, and a mature hackberry in a Tulsa yard will reliably host a population. The tree also supports numerous moth species, and the dense foliage provides forage for a wide insect community that in turn feeds insectivorous birds, especially during the nesting season.

Cavity Nesting & Habitat Structure

Hackberry is prone to developing heartwood decay as it ages, which creates natural cavities that are used by woodpeckers, chickadees, titmice, nuthatches, Eastern screech owls, flying squirrels, and bats. A dead or dying hackberry limb left in place (as long as it does not pose a safety risk) is a wildlife apartment building. The tree's dense, twiggy branching provides excellent nesting substrate for songbirds, and the rough bark hosts lichens, mosses, and a diverse community of small arthropods that are gleaned by foraging birds year-round.

Nipple Gall & Insect Ecosystem

Hackberry leaves are famously host to the hackberry nipple gall psyllid (Pachypsylla celtidismamma), a small insect that induces the formation of small, round, nipple-like galls on the underside of the leaves. The galls are conspicuous and sometimes alarming to homeowners who notice them, but they are entirely harmless to the tree — hackberry and its gall-makers have been co-evolving for millions of years, and a heavily galled tree is a healthy, ecologically functional tree. The psyllid larvae inside the galls are an important food source for chickadees, warblers, and other small insectivorous birds. The galls themselves are a fascinating miniature ecosystem, with parasitoid wasps, mites, and inquilines all living inside and on them. In the ecological sense, hackberry nipple galls are a feature, not a bug.

Horticulture & Care

[ site selection · planting · urban tolerance · maintenance · companion planting · food forest role ]

Site selection & planting

Hackberry is one of the most bulletproof native shade trees available for the NE Oklahoma landscape. It accepts nearly any soil, pH, moisture regime, and exposure, and it transplants readily from container or ball-and-burlap stock.

Sun: Full sun for best form. Tolerates light shade when young but will grow toward the light.
Soil: The tree's tolerance is extraordinary — from heavy red clay to sandy loam to rocky limestone soil to compacted urban fill. It tolerates a pH from 5.5 to 8.0+. The only condition it will not accept is soil that remains permanently waterlogged (stagnant water for months at a time). Seasonal flooding in a bottomland is fine; a permanently saturated septic field is not.
Spacing: 30–40 ft from buildings, driveways, and other large trees. The root system is extensive but not aggressively surface-rooting like silver maple.
Planting season: Bare-root in late winter (February–March); container-grown any time with irrigation. Fall planting (October–November) works well.
Urban considerations: Hackberry is one of the few trees that genuinely tolerates the heat islands, compacted soils, road salt exposure, and air pollution of urban Tulsa. If you need a large shade tree for a difficult urban or suburban site, hackberry is among your best native options, alongside Kentucky coffeetree and honey locust.

Maintenance

Water: Water young trees regularly (1 in/week) for the first two growing seasons. Once established, hackberry is moderately drought-tolerant and will survive Tulsa summers without supplemental water, though growth rate will slow during extended drought.
Pruning: Prune in late winter to develop a central leader and remove crossing, rubbing, and V-shaped narrow-crotch branches. Hackberry can develop multiple competing leaders; select and maintain a single central leader while the tree is young. Mature trees benefit from occasional crown thinning and removal of deadwood, but hackberry does not shed large limbs as aggressively as some soft-wooded species.
Witches'-broom: The twiggy branch-tip clusters (witches'-brooms) are caused by a combination of eriophyid mites and a powdery mildew fungus. They are cosmetic and harmless — do not attempt to prune or treat them. They are part of the tree's normal architecture and provide dense nesting sites for songbirds.
Fruit litter: Hackberry fruit drop in fall and winter can create a layer of small, hard drupes on sidewalks, driveways, and patios. The fruit is small enough that it is not a tripping hazard and decomposes reasonably quickly, but it is worth noting if the tree is planted directly over a paved surface that you want kept clean. The birds will clean up much of the fruit for you.

Pests & diseases

Nipple gall psyllid — harmless leaf galls (see Ecology section above). No treatment needed or recommended. The galls are part of the tree's ecological function.
Hackberry lace bug — can cause stippled, yellowing foliage in hot, dry summers. Rarely severe enough to warrant treatment; a strong jet of water on the leaf undersides in early summer knocks back populations.
Powdery mildew — a white, dusty coating on leaves in late summer and fall, often associated with witches'-brooms. Cosmetic; no treatment needed.
Armillaria root rot — can affect stressed trees in poorly drained soils. Not a common problem in well-sited hackberries.
Hackberry is NOT susceptible to Dutch elm disease — despite its elm-like appearance, hackberry is in a different family (Cannabaceae) and is unaffected by the disease that has devastated American elms.

Companion planting & food forest integration

Hackberry functions as a canopy or sub-canopy tree in a multi-story food forest or native landscape planting. Pairs well with: pecan, American sycamore, black cherry, and Shumard oak in a bottomland/high-canopy layer; pawpaw, American persimmon, and red mulberry in the understory layer beneath; roughleaf dogwood, American hazelnut, and spicebush in the shrub layer; and wild ginger, Solomon's seal, and Christmas fern as shade-tolerant groundcovers. Hackberry's light, dappled shade is easier to plant beneath than the deep shade of a dense-canopied oak or maple, making it a good choice for a food forest where you want productive understory plants.

Edible & Cultural Uses

Hackberry fruit is small — mostly seed with a thin layer of sweet flesh — but it is perfectly edible and has been consumed by Indigenous peoples across North America for thousands of years. The tree is not a "fruit tree" in the orchard sense, but its drupes are a genuinely useful wild food, especially in winter when little else is available.

Taste and eating: The thin, sweet, date-like flesh surrounds a large, hard seed. The flavor is pleasant — mildly sweet, with notes of caramel, raisin, and a hint of molasses. You eat the whole drupe, crushing the seed with your teeth, or you can suck the sweet pulp off the seed and spit the seed out. The seed itself is edible and contains a small amount of oil and protein, but it is hard and gritty. For most people, the fruit is a nibbling food, not a substantial meal — but for winter birds, it is life.
Traditional Indigenous use: Hackberry fruit was a significant winter food for many Native peoples of the Plains and Eastern Woodlands. The Comanche, Kiowa, and Osage of the Oklahoma region pounded the whole dried drupes — seed and all — into a coarse meal that was mixed with fat and formed into cakes. The Dakota and other Plains tribes stored hackberries in parfleche bags for winter use. The fruits were also boiled into a sweet mush or added to soups and stews as a flavoring and thickener.
Modern culinary possibilities: Hackberry drupes can be processed into a sweet, molasses-like syrup by simmering the fruit, mashing, and straining through a fine sieve to remove the seeds. The resulting liquid can be reduced to a syrup or fermented into a country wine. The fruit can also be dried, ground (seed and all), and used as a high-fiber, slightly sweet flour extender for breads and muffins. The flavor is distinctive and pairs well with cinnamon, nutmeg, and vanilla.
Wood and craft uses: Hackberry wood is light-colored, moderately hard, and not particularly rot-resistant, but it is used for furniture, cabinetry, and occasionally for smoking meat (it produces a mild smoke similar to maple or ash). The wood is not a premier lumber species, but it is workable and has been used for inexpensive furniture, crates, and fence posts. The inner bark was used by some Indigenous peoples for cordage and rough fabric.
Landscape and cultural note: Hackberry suffers from a reputation problem — it is often dismissed as a "trash tree" because it volunteers in alleys and vacant lots, can look ragged in old age, and lacks the prestige of an oak or a maple. This reputation is unfair. Hackberry is one of the most ecologically generous trees in the North American flora, and its tolerance of difficult urban conditions makes it one of the most useful trees for the modern city. A hackberry planted in a Tulsa front yard will, over its lifetime, produce literally millions of drupes, host thousands of caterpillars, and feed dozens of generations of cedar waxwings. That is not a trash tree — that is a keystone.

One tree, dozens of species. If you were to plant exactly one native tree in a NE Oklahoma landscape for maximum wildlife benefit, hackberry would be on the very short list, alongside oaks and black cherry. It feeds winter birds when nothing else does, hosts five butterfly species, provides cavity nesting and roosting habitat, supports a micro-ecosystem of gall insects and their predators, and will survive the soil compaction, drought, and neglect that kill lesser trees. It is not the prettiest tree, but it may be the hardest-working.

Photo Reference

// Celtis occidentalis — flowering habit
Wikimedia Commons

// Celtis occidentalis — foliage & form
Wikimedia Commons

// Celtis occidentalis — flower detail
Wikimedia Commons

// Celtis occidentalis — in habitat
Wikimedia Commons

// Celtis occidentalis — fruit / seed
Wikimedia Commons

Sources & Further Reading

USDA NRCS PLANTS Database — Celtis occidentalis: plants.usda.gov/plant-profile/CEOC
Lady Bird Johnson Wildflower Center — Native Plant Database: wildflower.org — CEOC
Oklahoma State University Extension — Native Tree Selection for Oklahoma Landscapes (hackberry highly recommended for urban sites).
Tallamy, D.W. (2007). Bringing Nature Home. Timber Press — Celtis as a premier Lepidoptera host genus.
Dirr, M.A. (2009). Manual of Woody Landscape Plants. Stipes Publishing — thorough treatment of hackberry in cultivation.
Moerman, D.E. (1998). Native American Ethnobotany. Timber Press — extensive records of indigenous food and medicinal uses of Celtis fruit.
Wheeler, A.G. (2001). Biology of the Hackberry Nipplegall Maker. Cornell University Press — the ecology of the hackberry-psyllid relationship.
Wikipedia — Celtis occidentalis: en.wikipedia.org/wiki/Celtis_occidentalis (CC BY-SA 4.0; portions of the description, ecology and uses sections summarize Wikipedia content).

Hero photo: Rooted Revival. Strip photos courtesy of Wikimedia Commons contributors under their respective licenses (linked under each image).