Bur oak vs white oak: leaves, acorns, size, growth, lifespan and which to plant

Bur oak is the oak of the prairie edge, built for cold, drought and lime-rich soil, and it bears the largest acorn of any native oak in a deep, fringed cup. White oak is the great shade tree of the eastern forest, with wine-red fall color and a smaller acorn in a shallow, warty cup. Both belong to the white oak group, both are slow growers and both live for centuries. Bur oak is the choice for clay, gravel and dry, open ground. White oak wants deep, well-drained, acid soil, and it is hardy to zone 9, where bur oak stops at zone 8.

How to tell bur oak from white oak

Both oaks have rounded leaf lobes with no bristle, the mark of the white oak group, so the leaf’s outline and the acorn’s cup do the sorting:

The leaf and the acorn

A bur oak leaf is pinched near its middle, where two sinuses nearly cut it in half, and the lobes above them spread into a crown. A white oak leaf is oblong, with finger-like lobes whose sinuses vary from deep to shallow. Sprouts and shaded branches of bur oak can grow shallow-lobed leaves, so read several from the sunny outside of the crown. Which oak is this leaf sets both beside the other oaks with rounded lobes.

From late summer the acorn settles it. Bur oak’s deep cup covers half or more of a nut up to 2 inches long, and long scales fringe its rim. That fringe gives the tree both its names, bur oak and mossycup oak. A white oak acorn sits in a shallow, knobby cup, and which oak dropped this acorn measures both against the other eastern oaks.

Twigs and fall color

In winter the twigs tell them apart, stout and often corky on a bur oak, hairless and often shiny on a white oak. Winter identification reads the bark, buds and pith of a bare tree. In fall, a white oak can turn wine red, though not every tree colors well:

“In fall, color can range from uninteresting browns to beautiful claret reds.” (Missouri Department of Conservation, White Oak)

Size and growth rate

The two grow at the same slow pace and reach much the same size:

Both are rated slow growers, and our growth estimator gives them the same reading. A 3-foot sapling on an average site reaches about 22 feet in 20 years, 16 feet on a poor site and 28 on a good one. White oak has the name of a slow tree, and in the Central States its trunks thickened more slowly than those of three common red oaks.

Open ground or forest sets the shape of both. In the open, white oak keeps a short, stocky trunk under a wide-spreading, rugged crown, and bur oak becomes a very wide tree with low, heavy limbs. In a forest both grow tall, clear trunks, white oak under a compact crown and bur oak sometimes past 100 feet.

How long each lives

Both live for centuries, and white oak holds the longer record. Many bur oaks reach 300 to 400 years, and one in a Kentucky savanna was put at about 440. Bur oaks bear acorns up to 400, older than reported for any other American oak. White oaks of 600 years have been recorded.

Ages proved ring by ring run shorter. The Eastern OLDLIST, a register of such ages, gives 464 years for a white oak in Virginia and 362 for a bur oak in Custer State Park, South Dakota. One entry there of 401 carries a note on the age in the list.

In a forest, that long life and its patience in shade are how white oak comes to rule a stand:

“White oak usually becomes dominant in the stand because of its ability to persist for long periods of time in the understory, its ability to respond well after release, and its great longevity.” (USDA Forest Service, Silvics of North America, White Oak)

Size is a poor guide to the age of either. A bur oak on a poor site may be 4 inches thick at 100 years, while one of the same age on deep, rich soil may be 30 inches. A big oak in the open is usually younger than it looks, and our tree age estimator gives a range of ages for a trunk you have measured.

Native range, soil and fire

Bur oak reaches farther north than any other American oak, from New Brunswick and Maine west to southern Manitoba and eastern Montana, and south through the Great Plains to Texas. White oak covers most of the East, from southwestern Maine and southern Quebec to southeastern Minnesota, and south to eastern Kansas, Texas and northern Florida. Bur oak grows wild in four states white oak does not reach: Montana, Wyoming and the two Dakotas. White oak grows wild in five that bur oak does not: Delaware, Georgia, Florida and the two Carolinas. The native trees we grow for North Dakota include bur oak and no white oak, and those for Georgia the reverse.

Bur oak is the tree of the prairie edge. It often forms the fringe between prairie and upland forest, and it is the main tree of the oak savannas of Wisconsin, Minnesota, Iowa and Illinois. Thick bark shields a grown bur oak from fire, and once a young tree is 12 to 15 years old it survives repeated burning. A younger one burned to the ground sprouts again from its deep roots as a low, knobby oak grub.

It is one of the most drought-resistant North American oaks, growing where as little as 15 inches of precipitation falls in a year. Its roots can be 4½ feet deep by the end of its first summer, and prairie bur oaks have rooted 10 to 20 feet down. On uplands it is often found on limestone and other lime-rich soils, and it takes alkaline ground better than most oaks.

White oak is the tree of the eastern forest. It grows on every upland slope but the driest, shallowest ridges, and it avoids poorly drained flats and wet bottoms. It does best on north- and east-facing lower slopes and in coves, in deep soil on the acid side. On alkaline soil its leaves yellow.

Where the two ranges overlap, the oaks cross, and the hybrid, Bebb oak, is widespread there. We do not grow it.

Acorns and wildlife

Both ripen their acorns in a single season. White oak acorns sprout almost as soon as they fall in September or October, while those of northern bur oaks often wait for spring. The seed sowing planner dates both routes for bur oak, sown in fall or chilled 30 to 60 days for spring.

Bur oak bears from about 35 years and gives good crops every 2 to 3 years. White oak bears at about 20 years in the open but seldom before 50 in a forest, and its good crops come only every 4 to 10 years, the pattern behind mast years.

White oak acorns are low in tannin, 0.5 to 2.5 percent, and deer, turkeys, blue jays, wood ducks, squirrels and black bears seek them. Bur oak acorns are considered palatable and nutritious, and red squirrels, deer, black bears, wood ducks, cottontails and mice eat them. Both oaks are pollinated by wind, and an acorn crop wants another oak nearby. A bur oak and a white oak pollinate each other, as the pollination planner shows for the pair.

Which to plant where

Choose by the ground first, then by the zone and the room:

• Lime, clay, sand, gravel or drought: bur oak, which takes lime, drought and city air better than most oaks and is widely planted in shelterbelts on the plains.
• Deep, well-drained soil on the acid side: white oak, as the shade tree of a large yard or the heart of a wildlife woodland.
• Wet ground: neither. Bur oak takes a brief spring flood on bottomland, but standing water kills it, and white oak does not take wet ground.
• Zone 9: white oak alone, since bur oak is rated to zone 8.
• Salt spray: white oak, which resists salt spray and a brief flood of salt water.

Bur oak needs a big lawn, a park or a pasture, where its broad crown has room:

“The stately bur oak, native to the Midwest, is a great choice as a shade tree and for specimen plantings in parks, spacious yards, and other large areas.” (The Morton Arboretum, Bur oak)

Set bur oaks 60 feet apart and white oaks 50, and keep either 40 feet from a wall and more than 50 feet from overhead wires. The planting-site check tests a bur oak 40 feet from a wall, and the companion species tool names the shrubs that take a white oak’s shade. Keep white oak clear of later digging or paving, since compaction, fill and trenching harm its roots.

Both drive a taproot down in their first summer, so plant either one young. White oak is difficult to transplant, and the sources split on bur oak. The Morton Arboretum lists bur oak as a tree that transplants well, while NC State Extension says its long taproot makes it difficult to transplant.

What we grow

Blue Whale Trees grows both oaks from seed and sells each as saplings and as acorns to sow:

• Bur oak: for lime, clay, drought and open ground, in full sun or light shade. Zones 3 to 8, 60 to 80 feet.
• White oak: for deep, well-drained soil on the acid side and centuries of shade. Zones 3 to 9, 50 to 80 feet.

Both are in Classic Oaks, the oaks every yard and woodland knows. Their acorns are among the acorns, nuts and seed collected from the same parent trees as the saplings. A search of the shop for oak lists every oak we grow, and which oak to plant matches the rest to the ground.

Common questions

Do bur oaks grow fast?

No, bur oak is a slow grower, about a foot a year in our growth estimator, and shelterbelt trees on the northern Great Plains grew about as much. A 3-foot sapling on an average site reaches about 22 feet in 20 years.

How fast does a white oak grow?

About a foot a year, the same slow rate as bur oak, though a seedling on ideal ground can make 2 feet or more. In the Central States its trunk added only 1.2 to 1.8 inches of diameter in ten years.

How long do bur oaks live?

Many live 300 to 400 years and go on bearing acorns to about 400. White oak can live longer, and trees of 600 years have been recorded.

How deep are bur oak roots?

A bur oak’s roots can be 4½ feet deep by the end of its first summer, and prairie bur oaks have rooted 10 to 20 feet down. That deep start helps it stand drought, and it is why the tree is best planted young.

How big is a bur oak acorn?

It is 1 to 2 inches long, the largest of any native oak, in a deep, fringed cup that covers half or more of the nut. Acorns from northern trees are about half the size of southern ones.