The classification of Redwood as a softwood or hardwood often causes confusion because these terms suggest a difference in physical firmness. In wood science, however, the terms “softwood” and “hardwood” are not measures of physical hardness or density. Instead, these classifications are based entirely on the reproductive structure of the tree. This botanical distinction is rooted in the evolutionary history and cellular makeup of the tree.
The Definitive Classification of Redwood
Redwood, specifically Coast Redwood (Sequoia sempervirens), is definitively classified as a softwood. It belongs to the group of trees known as gymnosperms, or conifers, which are cone-bearing plants that typically feature needle-like, evergreen foliage. This classification is absolute and is not dependent on the wood’s practical performance or density in construction. Redwood shares this botanical classification with other common conifers like pine, spruce, and fir.
Understanding the Botanical Difference
The fundamental distinction between softwoods and hardwoods lies in their reproductive structures and cellular anatomy. Softwoods are derived from gymnosperms, which produce “naked seeds” in cones. Hardwoods originate from angiosperms, which are flowering plants that produce seeds enclosed in a fruit or shell.
The most significant difference is visible under a microscope in the wood’s structure. Softwoods possess a simple cellular structure, primarily composed of long, narrow cells called tracheids. These tracheids perform the dual function of water transport and structural support.
Hardwoods feature a more complex structure, including specialized cells called vessel elements, or pores. These vessel elements are dedicated solely to water conduction, creating the distinct porous grain visible in hardwoods like oak or maple. Softwoods lack these vessel elements, relying almost entirely on tracheids for water movement. This lack of vessel elements is the defining anatomical characteristic that places redwood firmly in the softwood category.
Redwood’s Exceptional Durability and Practical Application
The confusion regarding redwood’s classification stems from its exceptional performance in construction, which often surpasses that of many hardwoods. Redwood’s resilience is attributed to the high concentration of natural chemical compounds known as extractives, particularly tannins, found within its heartwood. These tannins are responsible for the wood’s reddish-brown color and provide a natural defense mechanism.
These extractives create strong resistance to decay-causing fungi and insect infestation, making redwood one of the most durable softwoods available. This resistance is not uniform across the entire tree trunk. The highly durable portion is the heartwood, the dense inner core where the tannins are deposited.
The outer layer, known as the sapwood, lacks these protective chemicals and is much less resistant to decay. When selecting redwood for outdoor use, such as decking, siding, or fencing, heartwood lumber is preferred because its natural durability allows it to maintain structural integrity for decades without chemical treatment.