Wood is classified as either hardwood or softwood, depending on the seed type from which a woody plant grows. Hardwood is further broken down into two subclasses: monocotyledoneae, or monocot; and dicotyledoneae, or dicot. Of more than 10,000 classified trees, only 500 are softwoods. Wood is also classified by use, size and manufacturing.
Hardwood plants are defined by their seeds, which are distinguished by a covering. Fruit seeds, for example, are enshrouded in the fruit. Another example of a hardwood seed is the acorn, which is a seed with a tiny beret-like cap. The scientific term for this type of seed is "angiospermae." Hardwood varies in grain, ray prominence and coarseness.
Monocot vs. Dicot
Monocot and dicot are two subclasses of hardwood trees. Monocot seeds have one leaf attached to each seed. Bamboo, rattan and palm are three types of monocots used commercially. Bamboo is increasingly available for flooring and kitchen uses. It is also touted as an environmentally sustainable hardwood because it grows quickly. Dicots have two leaves attached to each seed. Trees can easily be identified as dicots if they lose their leaves in autumn.
Needle-bearing conifer trees are softwood trees. The term "softwood" does not necessarily mean that the wood itself is softer than hardwood. Some softwoods are harder than some hardwoods. The distinction is one of anatomy. Softwoods have fewer cell types than hardwoods. Softwoods are simply less dense than hardwoods. Pines, cedars and cypress trees are common softwoods.
Wood must be dried either by the sun or in a kiln to be suitable for commercial use, especially as lumber. Lumber is classified based on use, size and extent of manufacture. Subclasses for use include yard lumber, for ordinary building purposes; structural lumber, which is at least 2 inches thick; and factory or shop lumber, which is used to make furniture and carved items. Size subclasses include boards, dimensions and timbers. Manufacturing extent subclasses include rough lumber, where the saw edges show; dressed lumber, for wood smoothed by a planing machine; and worked lumber, for dressed wood that is ship-lapped, matched or patterned.
- Sawdust on the Floor: Wood Classification -- Hard or Soft?
- University of Kentucky College of Agriculture: "Scientific Classification of Trees: An Introduction for Wood Workers"; James E. Reeb
- Integrated Publishing: Lumber Classification
- The Columbia Encyclopedia: Wood; 2008
- University of Tennessee, Knoxville: Hardwoods and Softwoods