What causes grain in lumber?

Grain in lumber refers to the pattern and texture that can be seen on the surface of the wood, which is primarily influenced by the annual rings of the tree. These rings are formed as the tree grows each year, and they consist of the early wood (which forms during the spring and has a lighter, wider appearance) and late wood (which forms in the summer and tends to be denser and darker). The variation in the growth rate, influenced by factors such as climate conditions and soil fertility, contributes to the specific patterns observed in the grain of the lumber. Each ring reflects a year's growth, making it a key element in determining the appearance and performance characteristics of the wood.

While tree species also plays a role in defining the characteristics of the grain, including its density and workability, it is the annual rings that most directly create the visual and textural patterns known as grain. Moisture content and age of the tree have impacts on overall wood quality and performance, but they do not specifically define the grain patterns as the annual rings do.