The Strongest Wood Grown In American Forests

Shagbark hickory takes the top spot for bending strength among the commercial timbers of American forests. Forest Service engineers tested small, knot-free beams until they broke. Shagbark averaged 20,200 pounds per square inch (psi) when dried to 12% moisture content, the condition used for strength comparisons here unless otherwise noted.

But bending strength is only one measure of tough wood. Among the commercial species tested in the United States, black locust wins the crushing test and pignut hickory leads in hardness. Cherrybark oak is the stiffest, while live oak is the heaviest. Federal tests also examined Osage-orange beyond the commercial list. In its green, undried state, it beats every green hardness figure on that list.

Shagbark Hickory

The Forest Service's own tree manual says no commercial wood equals the true hickories in combined strength, toughness, hardness, and stiffness. Shagbark hickory backs it up with the best single bending score in the agency's table of commercially important American woods. Shagbark reached 20,200 psi. Northern red oak, the everyday benchmark here, managed 14,300 psi on the same test.

Shagbark grows across most of the eastern United States, reaching southern Maine, southeastern Minnesota, and eastern Texas. Furniture, flooring, and tool handles take most hickory lumber. Lab staff note that tool handles need shock resistance. Ladder rungs and dowels draw on the same strength, hardness, and shock resistance. Hickory also heats homes. Its charcoal gives food the flavor sold as hickory-smoked.

Pignut Hickory

Pignut hickory shares most of shagbark's eastern range and trails it in bending by just 100 psi. On hardness, the order flips. Hardness is the force needed to press a steel ball 0.444 inch across halfway into the wood. Pignut took 2,140 pounds of force, the highest side-hardness value on the list. Mockernut hickory came next at 1,970. Pignut also tops the list in work to maximum load, a gauge of strength and toughness combined.

Some pignut goes into home heating fuel. Standing hickories often carry mineral streak, an internal discoloration that agency silviculturists name as a major reason so few of them meet trade specifications.

Black Locust

The crushing test belongs to black locust. Engineers squeeze a short block end to end, along the grain, until it gives way. Locust held 10,180 psi, the only crushing value above 10,000 anywhere in the table. Shagbark came second at 9,210.

Black locust grows in two separate pockets. The eastern one follows the Appalachian Mountains from central Pennsylvania to northern Georgia, and the other covers the Ozark Plateau and the Ouachita Mountains farther west. Fence posts, mine timbers, poles, and railroad ties all appear among its listed uses. Shipbuilders also made treenails from it, the wooden pegs that fastened hull timbers.

Cherrybark Oak

Across the bottomlands of the South, cherrybark oak claims the best loamy ridges and well-drained terraces. Its range spans the Coastal Plain from southeastern Virginia west into Texas, then runs north up the Mississippi River valley into southern Illinois and Indiana.

Cherrybark wins on stiffness. Stiffness tracks how much a beam flexes under a load from which it fully recovers, and cherrybark flexes least. It scored 2.28 million psi. Pignut hickory sat just behind at 2.26 million, and northern red oak trailed at 1.82 million.

Forest Service silviculturists call cherrybark an excellent timber tree for its heavier, stronger wood. On the federal list, it far outstrips its relative southern red oak, which reached only 10,900 psi in bending. Cherrybark reached 18,100 psi, higher than any other red oak tested, and it goes into furniture and interior finish.

Live Oak

In 1828, the federal government set aside a peninsula between Pensacola Bay and Santa Rosa Sound in Florida to grow live oak. Park Service historians call that reservation the first national tree farm, and the wood it protected still tops the commercial list on weight.

Live oak overlaps cherrybark's range but keeps to the lower Coastal Plain, out to Texas and down into the Florida Keys. Live oak has a specific gravity of 0.88. It also leads every species in shear strength and in resisting a load pressed across the grain. Forest Service fire ecologists describe the wood as heavy and strong and note its past use in shipbuilding.

The frigate USS Constitution shows the connection. Shipwrights built its inner hull, dating to 1795, from live oak lumber. The old Florida reservation now belongs to Gulf Islands National Seashore, a Park Service unit rather than a national forest.

Longleaf And Slash Pine

Fire does little harm to a longleaf pine once it clears the seedling and early height-growth stages. Longleaf also shares ground with live oak. Longleaf held 8,470 psi under crushing, the best mark among the conifers. Slash pine, its Coastal Plain neighbor, topped the softwoods in bending at 16,300 psi. Lab staff rate longleaf and slash heavy, strong, stiff, and hard. Silviculturists call longleaf well suited to poles, piling, posts, and sawlogs.

Longleaf ranges across the Atlantic and Gulf Coastal Plains, and Forest Service researchers have worked to restore it on the Kisatchie National Forest in Louisiana. The same researchers describe longleaf forests that once formed a major ecosystem across the Southern United States.

Western Larch

Winter leaves western larch bare, because this conifer sheds its needles. Far from the southern pines, its range centers on the upper Columbia River Basin of northwestern Montana, northern Idaho, and northeastern Washington. Among the western conifers tested, larch leads in crushing strength at 7,620 psi. Larch is also the hardest of them at 830 pounds, although Douglas-fir from the northern interior wins bending by a whisker, 13,100 psi to 13,000.

Larch goes into lumber, fine veneer, utility poles, and mine timbers. The living tree handles fire well too. Mature larches are the most fire-resistant trees in the Northern Rockies by federal account, thanks to thick bark, high open branching, and foliage that burns poorly.

Osage-Orange

Thorny hedgerows of Osage-orange once fenced livestock across the Great Plains. The tree never made the commercial strength table, but federal tests from the 1930s measured it anyway. Freshly cut, or green, Osage-orange needed 2,040 pounds in the hardness test, more than any green value in the commercial table. Shellbark hickory leads that group at 1,670. In green bending, Osage-orange reached 13,700 psi, a hair behind black locust at 13,800.

The tree's native range is a narrow belt across eastern Texas, southeastern Oklahoma, southwestern Arkansas, and the northwest corner of Louisiana. Its wood is hard, durable, and resistant to decay, and fence posts are its primary use. The Osage people used the wood for bows and for dye. Osage-orange is not the densest wood in American forests, though, and the same 1930s tables list two different Florida trees as ironwood. One of them, black ironwood, is a native Florida tree whose specific gravity botanists put near 1.3, which makes it heavier than water.

Strength Depends On The Test

No single American wood wins every test. Shagbark hickory carries the bending title, and black locust holds the crushing record. Hardness goes to pignut hickory among wood tested at 12% moisture content, with Osage-orange ahead of every green figure in the commercial table. Live oak outweighs every commercial species. Longleaf, slash pine, and western larch lead their own conifer ranks. Beyond the commercial list, Florida's black ironwood grows wood heavier than water.