The acorn is rather large being about an inch and a quarter in length and usually about half as broad as long; has a shallow cup covered with pointed sometimes elongated scales.
This oak is one of the most important hardwoods of the far Northwest. It is often compared with the eastern white oak, but its physical properties fall below that species in some important particulars. The two woods weigh about the same, but the eastern species is stronger and more elastic, and is of better color and figure. All oaks season somewhat slowly, but the Pacific post oak is hardly up to the average. It is a common saying that it must remain two years on the sticks to fit it for the shop, but that time may be shortened in many instances. Checking must be carefully guarded against.
Some of this oak is exceedingly tough, and when carefully sorted and prepared it is excellent material for heavy wagons; but the best comes from young and comparatively small trees. When they attain large size they are apt to become brash. The tree usually grows rapidly, and is not old in proportion to the size of its trunk. An examination of the wood shows broad bands of summerwood and narrow, very porous springwood. The medullary rays are broad and numerous, and ought to show well in quarter-sawed stock; but it does not appear that much quarter-sawing has been done.
Practically all of this species cut in the United States is credited to Oregon in the census of sawmill output in 1910. The cut was 2,887,000 feet, and was produced by fourteen sawmills, while in Washington only one mill reported any oak, and the quantity was only 4,000 feet. On the northwest Pacific coast it comes in competition with eastern oak and also with Siberian or Japanese oak.
Basket makers put this wood to considerable use. Young trees are selected on account of their toughness. The wood is either split in long, thin ribbons for basket weaving, or it is first made into veneer and then cut in ribbons of required width. The largest users are furniture makers, but boat yards find it convenient material and it takes the place of imported oak for frames, keels, ribs, sills, and interior finish. It is durable, and it may be depended upon for long service in any part of boat construction. Its toughness fits it for ax, hammer, and other handles. It is far inferior to hickory, but on the Pacific coast it can be had much cheaper. Its strength and durability make it one of the best western woods for insulator pins for telephone and telegraph lines. It is worked into saddle trees and stirrups.