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// SPECIES PROFILE · TREE · NATIVE · POLLINATOR

Common Hackberry

Celtis occidentalis

The Common Hackberry is one of the toughest, most adaptable native trees in eastern North America — a rugged shade tree that thrives in urban conditions, heavy clay, drought, and occasional flooding with equal indifference. Celtis occidentalis is a member of the Cannabaceae (the hemp family, surprisingly), and while it will never win a beauty contest for its form — the crown is often described as "informal" or "irregular" — it is nearly unrivaled as a wildlife tree. Its sweet, date-like berries feed more than 40 species of birds, its foliage hosts the caterpillars of five butterfly species including the tawny emperor and question mark, and its deeply ridged, corky bark provides winter foraging substrate for brown creepers and nuthatches. In NE Oklahoma, it is a premier choice for a low-maintenance shade tree that doubles as a living bird feeder.

// QUICK FACTS
Family
Cannabaceae (hemp family — yes, related to Cannabis)
Life cycle
Deciduous tree
Native range
Eastern & central N. America — Quebec to GA, west to the Rockies; all of OK
USDA hardiness
Zones 2–9 (Tulsa = 7a/7b)
Mature size
40–60 ft tall, 30–50 ft wide; broadly rounded crown
Bloom
April – May; small, greenish, wind-pollinated flowers
Fruit
Round drupes, 1/4–3/8 in, orange-red to dark purple; ripens Sept–Oct; persists into winter
Sun
Full sun to part sun
Soil
Any soil — clay, loam, sand, alkaline, compacted; pH 5.5–8.0+
Water
Low to medium; very drought-tolerant once established
Wildlife
Host for 5 butterfly spp. · berries for 40+ bird spp. · winter bark foragers
Notable
Distinctive corky, warty bark; virtually indestructible in the urban landscape
Common Hackberry (Celtis occidentalis) showing distinctive corky, warty bark and broadly oval serrated leaves
Celtis occidentalis — the unmistakable corky, warty bark is the best winter identification feature of this rugged native tree. Photo: Rooted Revival.

Identification

[ field key — bark · leaf · fruit · form ]

Bark & Form

The bark is the tree's most distinctive feature. On mature trunks, the bark is light gray to grayish-brown with conspicuous, irregular, corky ridges and warty projections that give it a uniquely rough, knobby texture unlike any other native Oklahoma tree. This bark pattern is present even on relatively young trees and makes winter identification easy. The tree has a broad, rounded to irregular crown with a short trunk that often divides into several large, ascending branches. The overall silhouette is that of a large, somewhat untidy shade tree.

Leaves

Alternate, simple, ovate to lance-ovate, 2–5 in long, with a strongly asymmetrical base (one side of the leaf attaches lower on the petiole than the other) and a long, tapering tip. The margins are sharply serrated except near the base. The upper surface is medium green and rough to the touch (scabrous) — like very fine sandpaper. The underside is paler and softly hairy along the veins. Fall color is an unremarkable soft yellow. The leaves are often disfigured by hackberry nipple gall, a small, cylindrical gall caused by a psyllid insect that is entirely cosmetic.

Flowers & Fruit

The flowers are small, greenish, and inconspicuous, borne in early spring (April–May) as the leaves emerge. They are wind-pollinated and of little interest to pollinators. The fruit, however, is ecologically critical: each flower develops into a round, fleshy drupe about 1/4–3/8 in in diameter that ripens from green to orange-red to dark purple in September and October. The thin, sweet flesh surrounds a single, large, hard, bony pit. The drupes hang on slender stalks and persist on the tree well into winter, providing an extended food resource for birds when other fruits have been exhausted. The flavor is similar to a date or raisin.

Witches' Broom

Hackberry is frequently affected by witches' broom — dense, abnormal clusters of twigs caused by a combination of a powdery mildew fungus (Sphaerotheca phytoptophila) and an eriophyid mite. These dense branch clusters are unsightly but do not seriously harm the tree, and they actually provide additional nesting sites and cover for birds. In a wildlife-focused planting, they are a feature, not a flaw.

Habitat & Range in NE Oklahoma

Celtis occidentalis has an enormous native range extending from the Atlantic coast to the Rocky Mountains and from southern Canada to the Gulf states. It is native throughout Oklahoma and is especially common in bottomland forests, floodplain terraces, and the rich alluvial soils of river valleys. In NE Oklahoma, it is a common component of the Arkansas, Verdigris, and Illinois River bottomlands, where it grows alongside sycamore, cottonwood, green ash, and boxelder. However, its adaptability is such that it is equally at home on dry, rocky upland sites, in compacted urban soils, and in the alkaline clay of suburban Tulsa yards.

Hackberry's tolerance of nearly any soil condition, drought, wind, ice, and urban pollution has made it a common street and shade tree across the region, though it is less frequently planted today than in the mid-20th century. It is an outstanding, low-maintenance choice for a large shade tree in a NE Oklahoma wildlife garden, windbreak, or riparian buffer.

Ecology & Wildlife Value

[ butterfly host · bird food · mammal forage · urban ecology ]

Butterfly Host

Hackberry is the essential larval host for at least five butterfly species: 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 relationship is obligate: these species cannot complete their life cycles without hackberry foliage. The caterpillars feed on the leaves, and their presence is a primary reason to include hackberry in any NE Oklahoma landscape.

Birds

The persistent winter drupes are among the most important emergency food sources for birds. Over 40 species are documented consumers, including Northern cardinal, cedar waxwing, American robin, Eastern bluebird, mockingbird, brown thrasher, yellow-rumped warbler, Northern flicker, and pileated woodpecker. The berries' high sugar and fat content provides critical energy during cold weather, and their persistence into late winter makes them a survival food when other fruits are gone.

Mammals & Other Wildlife

White-tailed deer, raccoons, opossums, foxes, and squirrels all eat the drupes. The rough, corky bark provides excellent foraging substrate for brown creepers, white-breasted nuthatches, and downy woodpeckers that probe the deep crevices for overwintering insects and spiders. The dense witches' broom clusters offer secure nesting sites for mourning doves, cardinals, and other shrub-nesting songbirds. Hackberry is also a preferred roosting tree for turkey vultures and black vultures.

Urban & Riparian Ecology

Hackberry is one of the most pollution-tolerant native trees and is widely used in urban forestry. Its extensive, fibrous root system stabilizes streambanks in riparian zones. The tree's tolerance of soil compaction, salt (to moderate levels), and reflected heat makes it one of the few large native trees that can survive and thrive in the harsh conditions of urban parking lots, street tree wells, and commercial landscapes.

Horticulture & Care

[ site selection · planting · maintenance · cautions ]

Site selection & planting

Hackberry is among the easiest native trees to establish. It accepts nearly any soil, any drainage, and any exposure except deep shade. Plant bare-root seedlings in late winter or early spring, or container-grown specimens anytime. Hackberry transplants readily and establishes quickly.

Maintenance

Landscape value

Hackberry is not a "specimen tree" for the front lawn in the way that an oak or maple might be. It is better understood as a workhorse species: an indestructible shade tree for difficult sites, a living bird feeder, and a butterfly nursery. Plant it in the back corner of the yard, on the windward side of a windbreak, along a creek bank, or in a wildlife hedgerow where its informal form and fruit litter are features, not problems.

Edible & Cultural Uses

Hackberry drupes are edible for humans, though they are small, dominated by a large pit, and generally more suited to snacking in the field than to serious harvest. The flavor is sweet and pleasant, similar to a date or raisin, and the thin flesh is high in sugar, fat, and protein.

Sources & Further Reading

Hero photo: Rooted Revival.