Post oak

Appalachian-Blue Ridge forests

Arizona Mountains forests

Atlantic coastal pine barrens

Blue Mountains forests

Central Pacific Northwest coastal forests

Central-Southern Cascades Forests

Colorado Rockies forests

Appalachian mixed mesophytic forests

What it needs

Conditions

Light

Full sun

Water

Low water

Spacing

35 ft

Habit

Medium deciduous oak, 35 to 50 feet tall and about as wide, with a dense rounded crown and heavy, often crooked, low branching. Open-grown trees are broad and gnarled rather than upright, and on a poor dry site an old post oak can look far younger and smaller than it is.

Care tips

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Protect the root zone of an existing post oak absolutely. Grading, trenching, compaction and added irrigation near a mature tree are the usual causes of the slow decline that kills it years later - and no replacement planting will catch up in your lifetime.

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Plant it small and once. It transplants badly, so a container seedling set in its final position will outperform a large moved specimen.

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Do not irrigate it like a lawn tree. This is a dry-upland species; consistently moist ground and poor drainage are what it cannot tolerate.

Lifecycle

Planting

Plant in spring in full sun. Missouri Botanical Garden puts its best growth in rich, moist, acidic, well-drained loam while noting it adapts to a wide variety of soils, and its documented tolerances are drought, dry soil and shallow rocky soil - which is where it is actually useful. Give it good drainage above all; the one condition it will not accept is wet ground.

Transplanting

Difficult, and this is the species-defining caution. Post oak resents root disturbance to an unusual degree, which is why mature trees decline and die after nearby construction, grading or trenching. Plant small stock and site it once. If you already have a mature post oak, protecting its root zone is worth more than anything you could plant to replace it.

Early growth

Slow. Prune for structure early, because the natural habit is low, heavy and crooked and the decisions get harder as the limbs thicken. Do not try to accelerate it with feeding and irrigation - a forced post oak is a weak one.

Maturity

Long-lived and low-maintenance once established. Missouri Botanical Garden lists oak wilt and anthracnose among its problems along with the usual oak insects. Prune in late winter only, and never in spring in an oak-wilt region. The commonest cause of death in a garden setting is not disease but disturbance of the root zone.

Propagation

From acorns, which as a white-group oak germinate immediately on falling with no dormancy - sow the day they drop rather than storing them. Sow them where the tree is to stand if you can, given how badly the species takes to being moved.

Pollination

Wind-pollinated

Monoecious and wind-pollinated - yellowish-green male catkins and inconspicuous female flowers on the same tree in April as the leaves emerge. A single tree sets acorns alone once mature enough to bear, which may take 25 years.

Plants don't grow alone

Larval host

Moth

Buck moth (Hemileuca maia)

Buck moth is an oak specialist of dry, sandy and scrubby oak country, and post oak barrens and savannas are among its characteristic habitats. Its autumn adult flight is one of the few conspicuous insect events on this kind of dry ground.

Larval host

Moth

Polyphemus moth (Antheraea polyphemus)

Polyphemus moth is a documented oak feeder. Oaks are the most important native larval host genus for Lepidoptera in North America, so even a modest post oak carries a disproportionate share of the caterpillar biomass on a dry upland site.

Larval host

Moth

Imperial moth (Eacles imperialis)

Imperial moth larvae feed on oak foliage across the southern and central range this species occupies.

Seed forage

Mammal

Eastern gray squirrel (Sciurus carolinensis)

Squirrels take the small sweet acorns readily. As with the other white oaks the acorns germinate on falling and so are eaten rather than stored, which makes the tree a food source more than a caching partner.

Seed forage

Mammal

White-tailed deer (Odocoileus virginianus)

Deer prefer low-tannin white-group acorns, and post oak mast is taken early in the drop. Across the Cross Timbers it is one of the defining autumn food resources.

Seed forage

Bird

Eastern songbirds (multi-species) (multiple species (Passeriformes))

Wild turkey, jays and woodpeckers all take the three-quarter-inch acorns whole. The dense low crown also offers better nesting cover than the high open canopies of the larger oaks.

For people

Edible with preparation

The acorns are edible after leaching and, as a white-group oak, comparatively low in tannin and among the more palatable wild acorns. They are small, to three-quarters of an inch, and still want soaking or boiling in changed water before use as flour. Raw acorns and foliage in quantity remain a risk to horses and livestock. The species' historic value was structural rather than edible - its dense rot-resistant wood was the standard fence post that gave it the name.

Native range

Native

Naturalized

Native across 28 US states; naturalized in 1 US state.

Worldwide native range.

AHS heat range

3-11

Native ecoregions

Naturally belongs in 16 ecoregions - its native range crosses a state or province each one spans (not necessarily this exact habitat).

Appalachian-Blue Ridge forests

Atlantic coastal pine barrens

Central Tallgrass prairie

Chihuahuan desert

Cross-Timbers savanna-woodland

Eastern Great Lakes lowland forests

Edwards Plateau savanna

Flint Hills tallgrass prairie

Mississippi lowland forests

A dense, conical-to-narrow-pyramidal evergreen tree native to eastern and central North America, prized as a screening and foundation conifer. Flat, fan-like sprays of scale-like, aromatic yellow-green foliage clothe the tree from the ground up, and red-brown bark exfoliates on mature trunks. Wild trees can reach 40 to 60 feet but cultivated plants typically stay near 20 to 30 feet; small urn-shaped cones and dense evergreen cover make it valuable food and shelter for birds.

Climate notes

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Native to the southeastern and south-central United States, on lower mountain slopes, dry rocky uplands, glades and coastal plains. POWO returned HTTP 403 for this species, so the WGSRPD range was taken from the World Checklist of Vascular Plants rows served through GBIF, the same Kew dataset, verified in this batch against a species POWO did answer for.

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District of Columbia appears in the Wildflower Center occurrence list but not in the Kew native range, so it is carried in the ESTABLISHED layer rather than the native one.

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In Missouri, Missouri Botanical Garden records it in dry soils on rocky upland slopes, woods and glades, and also in moist soils along streams - a wider site range than the drought-tolerant reputation alone would suggest, though the dry upland is where it dominates.

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The Cross Timbers of Texas and Oklahoma are effectively a post oak formation, and one of the largest surviving areas of ancient forest in the central United States. Trees there are commonly centuries old and still modest in stature, which is the clearest illustration of how slowly this species trades growth for endurance.

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Its documented tolerances are drought, dry soil and shallow rocky soil, and the corresponding limit is wet ground and root disturbance. A post oak on a site that is later graded, trenched or irrigated will often decline over several years - the delay is long enough that the cause is regularly missed.

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Plotwright assigns an editorial AHS heat range of 3-11, reasoned from the cited GBIF/WCVP range and Missouri Botanical Garden cultivation notes rather than from the USDA zones above. Its northern and lower-mountain edge supplies cool summers but not the near-zero-heat conditions of the far north, while the Cross Timbers and dry south-central uplands demonstrate dependable long-hot-summer tolerance. The range stays below the tropical tier because its core remains temperate North America. This is a conservative Plotwright interpretation, not a copied AHS rating.

Similar plants

Browse lateral options with similar roles, light needs, size, or native-range overlap; these are not filtered for a better climate fit.

Thuja occidentalis

American arborvitae

A medium-to-large native shade tree of central and eastern North America, reaching 50 to 80 feet with an ovate-rounded crown and large, asymmetric heart-shaped leaves. In June it carries pale-yellow, intensely fragrant flowers on pendulous cymes - each cluster hung from a distinctive strap-like leafy bract - that ripen into pea-sized nutlets. The fragrant June bloom is a premier nectar source: Missouri Botanical Garden lists it as attracting bees and butterflies, and the Lady Bird Johnson Wildflower Center flags it as having special value to both native and honey bees.

The only native U.S. holly with both spiny green leaves and bright red berries - an upright, pyramidal, broadleaf evergreen tree that slowly matures to 15 to 30 feet in cultivation (to 50 feet in the wild). Thick, leathery, deep green leaves bear spiny marginal teeth, and pollinated female trees carry showy red-to-orange drupes that ripen in fall and persist through winter as bird food. This is the classic "Christmas holly" of wreaths and decorations.

A small-to-medium understory tree of dry, rocky eastern-North-American woods, named for its drooping clusters of papery, sac-like seed pods that resemble the fruit of hops. The birch-like, sharply-serrated leaves turn an undistinguished yellow in fall, and reddish-brown male catkins persist on the bare branches through winter. Also called ironwood for its extremely hard, dense wood; tough, low-maintenance, and drought-tolerant once established.

A tough, medium-sized native tree of the eastern and midwestern United States, grown as much for its showy edible orange fruit as for its distinctive thick, dark gray bark broken into rectangular blocks. Small urn-shaped white-to-greenish-yellow flowers open in May and June, and the sweet fruit ripens after frost. Largely dioecious - a female tree needs a male pollinizer nearby to set fruit - and notably drought- and walnut-tolerant once established.

Full sun / Part shade

A small native deciduous tree (or thicket-forming, suckering shrub) of eastern and central North America, grown for clouds of fragrant white 5-petaled flowers that open in March before the leaves and for the edible red plums that follow in early summer. It forms a broad, spreading crown with attractive dark reddish-brown twigs that sometimes carry thorny lateral branchlets. A documented larval host for swallowtails and other butterflies, with flowers of special value to native, bumble, and honey bees.