Hackberry

The only host plant for three American butterflies, a winter bird feeder that holds its sweet edible berries until February, and the toughest native shade tree there is - hackberry survives drought, wind, salt, clay, and city soil where nothing else will.

Full sun and almost any soil - hackberry is famously unfussy about clay, sand, alkalinity, salt, drought, and city conditions. Give it room for a 40-70 foot spreading crown, water it for two or three years, and train one leader.

Hackberry may be the least demanding shade tree in North America. Give it full sun or light shade and it will grow in nearly anything: heavy clay, dry sand, limestone and other alkaline soils, compacted parking-strip dirt, floodplain silt that goes underwater in spring, and roadside ground salted every winter. Its one preference is decent drainage, and even that is negotiable. It is wind-firm, drought-proof once established, and hardy from about zone 3 into zone 9.

The things that actually matter are room and structure. A mature hackberry reaches 40-70 feet with a wide, vase-shaped, arching crown, so site it well away from the house, the drive, and utility lines. Because it branches low and readily grows competing leaders, spend the first few winters picking one central leader and shortening its rivals — the old hackberries that split in storms are almost always the ones with two co-dominant trunks.

Water a new tree weekly through its first two or three summers and mulch a wide ring around it. After that, essentially stop. Do not fertilize, do not spray, and do not fuss. One siting note worth taking seriously: the berries stain, and in the South the woolly hackberry aphid can rain sticky honeydew for weeks — so do not plant one directly over a patio, a deck, or the spot where you park.

Almost none. Prune in late winter for structure only, tolerate the galls and brooms, never spray a butterfly host tree, and pull the seedlings that birds plant around the yard.

An established hackberry needs no watering, no feeding, and no protection. The only routine job is structural pruning in late winter: take out crossing and damaged limbs and any second leader while the tree is bare and you can see what you are doing. Do not try to prune out the witches' brooms — there are usually dozens and cutting them changes nothing.

The main discipline is restraint. Hackberry is a butterfly host tree, so chewed leaves are the point of growing it and any insecticide undoes the whole purpose. The nipple galls and witches' brooms that make some gardeners uneasy are genuinely harmless: decades of extension research finds no effect on growth, fruiting, or lifespan. If the look bothers you, the answer is to plant sugarberry (Celtis laevigata) instead, which gets far fewer of both, rather than to spray.

Two ongoing chores are worth expecting. Birds spread the seed everywhere they perch, so volunteer seedlings come up in beds and along fences — pull them small, when they come out easily. And the fruit drops and stains, so sweep pavement beneath the tree in late winter after the waxwings have finished.

Berries ripen brick-red from September and hang into winter. They taste like a date wrapped thinly around a stone - pick a handful to chew off a low branch, and leave the rest for the birds that depend on them.

Hackberries ripen from orange through dark brick-red to purple-brown starting in September, and unlike most fruit they do not fall — they hang on the twigs right through fall and winter, drying slightly as they go. Both fresh and dried are edible. Pick a few off a low branch and chew them gently: the thin flesh is sweet, dry, and distinctly date-like, one of the more pleasant wild fruits in North America.

The limitation is obvious the moment you eat one. Each berry is mostly a hard stony seed with only a skin of flesh around it, so this is a trailside nibble rather than something you gather by the bucket. The traditional preparation, used across the Great Plains and documented at archaeological sites going back thousands of years, was to pound the whole fruit — flesh, seed, and all — into a paste and mix it with fat or parched corn; the crushed seed is nutty and adds calcium and protein. If you try it, use a mortar or a sturdy food processor, never your teeth on a crown or a filling.

The far more important harvest is not yours. Because the fruit persists into January and February, a hackberry is a winter feeding station at the point in the year when birds are most desperate for calories. Take a handful and leave the tree to them.

Berries dry on the tree and keep for months as they are; gathered fruit air-dries easily and stores like a raisin. Seed for planting should be cleaned and sown fresh in fall, or refrigerated moist over winter.

Hackberries store themselves. Left on the branch they slowly dry into something between a raisin and a tiny date, staying edible for months — which is exactly why they carry birds through winter. Gathered fruit needs no processing: spread it in a single layer somewhere warm and airy for a few days, then keep it dry and cool in a jar. A whole-fruit paste, pounded with the seed, was traditionally shaped into cakes and stored dry; treat it like any low-moisture preserve and refrigerate or freeze it if you have made much.

For planting stock, clean the pulp off the stones and either sow them straight away in fall, or mix them with slightly damp sand and keep them in the refrigerator for two to three months of cold-moist stratification before a spring sowing. Do not let cleaned seed dry out hard on a shelf for a year and expect good germination — fresh, cold-conditioned seed is far more reliable, and the easiest route of all is simply to sow in fall and let winter do it.

Easiest from seed: clean ripe berries and sow the stones outdoors in fall, or cold-stratify them for two to three months and sow in spring. Birds propagate it for you, so transplanting a volunteer seedling is often the simplest route of all.

Seed is the standard method and it is easy. Gather ripe berries in fall, rub the pulp off the stony seeds, and sow them about an inch deep in fall right where the tree will grow or into a nursery bed, covered with hardware cloth so mice and squirrels do not take them. Winter cold supplies the two to three months of cold-moist stratification the seed needs, and the seedlings appear the following spring. For a spring sowing, do the same chilling in a bag of damp sand in the refrigerator.

Hackberry seedlings grow fast — often a foot or more in their first year — and transplant readily while small, which makes the easiest propagation of all simply moving a volunteer. Birds drop seed along fence lines and under perches constantly, so most yards within range of a mature tree already have seedlings coming up. Lift one in early spring while it is dormant and under a couple of feet tall, keep as much root as you can, and plant it where you want it. Named cultivars such as 'Prairie Pride' are budded or grafted by nurseries rather than grown from seed, since seedlings vary.

A keystone tree in the strictest sense: the sole larval host for three butterflies, a host for two more, and a winter fruit source when nothing else is left. The berries are a nutritious traditional human food, seed and all.

Hackberry's ecological value is unusually specific and easy to state. It is the only larval host for the hackberry emperor (Asterocampa celtis), the tawny emperor (A. clyton), and the American snout (Libytheana carinenta), and one of a short list of hosts for the question mark and the mourning cloak. Those are not obscure insects — the snout is the butterfly behind the famous mass migrations that darken Texas skies after summer rains. Plant a hackberry and you can reasonably expect those butterflies to find it; without one, they simply are not in the neighborhood.

Its persistent winter fruit is the second contribution and it is rare. Most native fruit is stripped by December; hackberries hang on into February, so waxwings, robins, mockingbirds, cardinals, bluebirds, flickers, and turkeys use them at the hungriest point of the year. Small mammals take the fallen fruit, and the shaggy corky bark and frequent cavities shelter bats, woodpeckers, and nesting birds.

For people, the fruit is a real if modest food. Ground whole, the flesh and crushed seed together supply sugars, protein, fat, and a notably high dose of calcium — hackberry stones are unusually mineral-rich, which is why charred seeds turn up so often in archaeological hearths across the Plains and Midwest.

One of the oldest documented human foods in North America - charred hackberry seeds appear in hearths going back millennia - and, more recently, the tough urban tree that replaced the ashes killed by emerald ash borer.

Hackberry has one of the longest food records of any North American tree. Because the stone is hard and mineralized, it survives fire and burial almost intact, so charred hackberry seeds are a recurring find in hearths and middens across the Plains, the Midwest, and the Southwest, some of them thousands of years old — and they also turn up in early Old World sites for the related European nettle tree. Plains peoples pounded the whole fruit into a paste and mixed it with fat or parched corn; the wood, pale and shock-resistant, was worked into tool handles, furniture, and crating.

In the modern landscape hackberry has had two lives. For most of the twentieth century it was a slightly disreputable tree, planted in shelterbelts and along highways and dismissed in gardens because of its galls and brooms. Then emerald ash borer destroyed the ash trees that lined much of the Midwest, and cities looking for a native replacement that could take drought, salt, wind, alkaline soil, and compaction found that hackberry took all of them. It is now widely planted as a street and park tree, and the native-plant movement has added the second argument: as a butterfly host, few trees in its range do more.

Nearly every hackberry complaint - warty galls, twiggy brooms, sticky honeydew, seedlings everywhere, stained pavement - is cosmetic or a siting problem, not a health problem. The tree itself is remarkably trouble-free.

Hard warty bumps all over the leaf undersides: hackberry nipple galls, made by tiny psyllids. Universal, cosmetic, and harmless — there is no practical spray for a large tree and none is needed. The adults drift indoors through window screens in fall, which is their only real nuisance.

Dense twiggy tangles at the branch tips: witches' broom, caused by an eriophyid mite and a powdery mildew working together on the buds. Also harmless. If the look genuinely bothers you, plant sugarberry (Celtis laevigata) or a selection like 'Prairie Pride' instead, both far less prone to it.

Everything under the tree is sticky, and the leaves have gone black: woolly hackberry aphid honeydew and the sooty mold that grows on it, a serious nuisance in the South and Southwest. Nothing you spray on a big tree will fix it; the answer is not to site a hackberry over a patio, deck, or parking spot in the first place.

Seedlings coming up everywhere: birds spread the seed from every perch. Pull them while small. Purple stains on the driveway: fallen fruit — sweep in late winter once the birds have finished. A big limb split out in a storm: almost always a tree with two competing leaders; prune young trees to one central stem, and have an arborist look at an old tree with a narrow, included fork. Chewed leaves and spiky green caterpillars: emperor and snout butterflies. That is success, not damage.

Hardy from zone 3 to zone 9 and adaptable almost everywhere in between - it is the native shade tree of choice for hot, dry, windy, alkaline, salted, or compacted sites where most trees fail.

Hackberry's range is enormous and its tolerance is wider still. Zones 3-5: fully cold-hardy across the northern plains and upper Midwest, where it is a standard shelterbelt and windbreak tree and handles bitter cold and constant wind. Zones 5-7: its heartland — a fast, reliable, long-lived shade tree for yards, streets, and parks, and increasingly the ash replacement of choice. Zones 7-9 (South and Southwest): excellent, though this is where sugarberry (Celtis laevigata) usually takes over as the better-adapted species, with cleaner foliage and far fewer galls; in the arid Southwest, netleaf hackberry (C. reticulata) is the desert-tough native.

What sets hackberry apart is the list of stresses it ignores: drought, high heat, hard wind, alkaline and limestone soils, heavy clay, salt spray and road salt, compaction, and periodic flooding. There is hardly a difficult site in the eastern two-thirds of the country where a hackberry will not grow. Its only real weaknesses are storm breakage in poorly structured old trees and the cosmetic galls, and both have straightforward answers — prune to one leader when young, and choose sugarberry or a named selection where appearance matters most.