There are hundreds of North American hardwood species, each with distinct characteristics. Natural hardwood products are never as uniform as wallpaper, for example but that's a major source of their charm. Heartwood, the oldest, densest, innermost section of the log, is ofter darker and richer in color than sapwood, which lies closest to the bark. Within each species, every tree is an individual. No two logs carry the same signature knots, burls, or mineral streaks. Their lumbers harmonize, but they vary in color, grain, and an unlimited range or natural details called character marks. The features within any single log are unpredictable. No two boards, even from the same log, are identical.
The most common natural characteristics seen are:
Hardwood character marks can add appeal for homeowners who appreciate natural materials. They record a life in the forest as well as showing that more of each tree harvested is used, responsibly, in lasting applications. They also extend the range of creative options for the homeowner, builder, architect, designer, and woodworker.
A log produces relatively few clear boards - pieces free of character marks and other distinguishing features. So boards with the no character marks rate the highest grades. Much of the remaining lumber offers very good value, and may be perfect for your particular project.