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Hardest Woods Native to the US

Trees in the United States and elsewhere are generally divided into softwoods and hardwoods. This is a loose classification that takes into account the hardness of the wood. In general, softwoods consist of mostly conifers, while the hardwoods are part of a larger grouping, called flowering plants. Nonetheless, there is a little bit of overlap, for the wood of the toughest pine can be denser than that of an aspen or cottonwood.

Why Is Wood Hard?
- The hardness of wood can be attributed to three characteristics of the cells of the tree trunk: the density of the cells, how much lignin is contained in the cell walls and the percentage of air pockets within the cell walls. First of all it is important to note that dried wood consists of dead cells that still hold their original configuration. The weight is due to the presence of cellulose and lignin, a brown carbon-based polymer, in the cell walls. Moreover, the density of wood is determined by the amount of solid material in relation to the quantity of air spaces found within the cell walls.
Hardwoods and Softwoods
- The wood of flowering plants differs from the wood of conifers in one key feature. The trunks of the flowering plants contains a specialized conductive cell, where the cell wall is filled with a thick fiber. These fiber cells are lacking in conifers, and since these cell walls tend to be very dense and heavy, the wood from the trunks of flowering plants tends to be denser than those of pines, fir, spruce, hemlock and junipers.
Specific gravity
- The density of wood can be mathematically calculated by measuring the specific gravity of a dried sample. When this is done and the numerical values are compared, several trees come out as being particular dense and hard. In the eastern half of the United States, it is the shagbark, hickory, persimmon and eastern ironwood that have the densest wood. However, these trees of the forest are easily surpassed by the mountain mahogany, hollyleaf cherry and Engelman oak, all of which are found in Southern California.
And the Winner Is
- According to Dr. W.P. Armstrong of Palomar College, desert Ironwood (Olneya tesota) is the hardest wood native to the U.S. With a specific gravity even greater than ebony, this small tree grows naturally in the Sonoran Desert of Southern California, southwestern Arizona and northwestern Mexico. Known as palo fierro in Spanish, this tree may obtain a height of 30 feet while living to be 1,500 years old. The wood was used by the Seri Indians to make tool handles and create carvings of plants and animals.

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