Celtis occidentalis
Celtis occidentalis, the Common hackberry, is a large tree native to North America.
Hackberry is easily distinguished by its cork-like bark with wart-like protuberances.  The leaves are distinctly asymmetrical and coarse-textured.  It produces small berries that turn orange-red to dark purple.  Hackberry is easily confused with sugarberry (Celtis laevigata) and is most easily distinguished by range and habitat; Hackberry also has wider leaves that are coarser above.

# Description
A large tree with a slender trunk, rising to the height of one hundred and thirty feet, is the Hackberry in the southern Mississippi valley area, but in the middle states it attains the height of sixty feet with a handsome round-topped head and pendulous branches.  It prefers rich moist soil, but will grow on gravelly or rocky hillsides.  The roots are fibrous and it grows rapidly.
It has an unmistakable bark pattern.
- Bark: Light brown or silvery gray, broken on the surface into thick appressed scales and sometimes roughened with excrescenses.  Branchlets slender, light green at first, finally red brown, at length become dark brown tinged with red.
- Wood: Light yellow; heavy, soft, coarse-grained, not strong.  Used for fencing and cheap furniture.  Sp. gr., 0.7287; weight of cu. ft., 45.41 lbs.
- Winter buds: Axillary, ovate, acute, somewhat flattened, one-fourth of an inch long, light brown.  Scales enlarge with the growing shoot, the innermost becoming stipules.  No terminal bud is formed.
- Leaves: Alternate, ovate to ovate-lanceolate, more or less falcate, two and a half to four inches long, one to two inches wide, very oblique at the base, serrate, except at the base which is mostly entire, acute.  Three-nerved, midrib and primary veins prominent.  They come out of the bud conduplicate with slightly involute margins, pale yellow green, downy; when full grown are thin, bright green, rough above, paler green beneath.  In autumn they turn to a light yellow.  Petioles slender, slightly grooved, hairy.  Stipules varying in form, caducous.
- Flowers: May, soon after the leaves.  Polygamo-mon cious, greenish.  Of three kindsstaminate, pistillate, perfect; born on slender drooping pedicels.
- Calyx: Light yellow green, five-lobed, divided nearly to the base; lobes linear, acute, more or less cut at the apex, often tipped with hairs, imbricate in bud.
- Corolla: Wanting.
- Stamens: Five, hypogynous; filaments white, smooth, slightly flattened and gradually narrowed from base to apex; in the bud incurved, bringing the anthers face to face, as flower opens they abruptly straighten; anthers extrorse, oblong, two-celled; cells opening longitudinally.
- Pistil: Ovary superior, one-celled; style two-lobed; ovules solitary.
- Fruit: Fleshy drupe, oblong, one-half to three-fourths of an inch long, tipped with remnants of style, dark purple.  Borne on a slender stem; ripesn in September and October.  Remains on branches during winter.

# Distribution
Hackberry is native to North America from southern Ontario and Quebec, through parts of New England, south to North Carolina-(Appalachia), west to northern Oklahoma, and north to South Dakota.  Hackberry's range overlaps with the sugarberry (Celtis laevigata), making it difficult to establish the exact range of either species in the South.

# Ecology
Hackberry grows in many different habitats, although it prefers bottomlands and soils high in limestone.  Its shade tolerance is greatly dependent on conditions.  In favorable conditions its seedlings will persist under a closed canopy, but in less favorable conditions it can be considered shade intolerant.
Hackberry is highly susceptible to fire damage.  The leaves are eaten by four gall-producing insects of the Pachypsylla genus, which do not cause serious damage to the tree.  A number of insects and fungi cause rapid decay of dead branches or roots of the tree.
The small berries, hackberries, are eaten by a number of birds and mammals.  Most seeds are dispersed by animals, but some seeds are also dispersed by water.

# Cultivation & Uses
Hackberry's wood is soft and rots easily, making the wood undesirable commercially, although it is occasionally used for furniture or other uses.  The berries, although edible, are small and out of reach, and are seldom eaten by humans.  Hackberry is only occasionally used as a street or landscaping tree, although its tolerance for urban conditions make it well suited to this role.

# History
Traces of Celtis have been found in the miocene rock of Europe.