Different types of construction projects call for different kinds of timber, and many people are familiar with the concepts of hardwood and softwood. Few people know why woods are split into these two categories, however, and they make the assumption that hardwoods are hard, while softwoods are soft. This distinction is incorrect: balsa wood, for example, is classified as a hardwood despite the fact that it is very soft and light. The two wood types are actually distinguished botanically, not by their end use or appearance.
In general, hardwood comes from a deciduous tree that loses its leaves annually, and softwood comes from a conifer, which usually remains evergreen. Hardwoods tend to be slower growing, and are therefore usually more dense, but not always. Softwood usually grows in huge tracts of trees which may spread for miles, while hardwoods tend to be found mixed with a variety of other species.
Softwood comes from a type of tree known as a gymnosperm. Gymnosperms reproduce by forming cones which emit pollen to be spread by the wind to other trees. Pollinated trees form naked seeds that are dropped to the ground or borne along the wind so that new trees can grow elsewhere. Some examples include pine, redwood, fir, cedar, and larch.
A hardwood is an angiosperm, which means that it makes enclosed seeds or fruits. Angiosperms usually form flowers to reproduce. Birds and insects attracted to the flowers carry the pollen to other trees, and when fertilized the trees form fruits such as apples or nuts and seeds like acorns and walnuts. Examples include maple, balsa, oak, elm, mahogany, and sycamore.
Both types of wood are used for everything from structural beams to decorative accents. Some woods within each category are favored for particular uses: maple and elm are common elements in flooring. Redwood is often used for decking and other outdoor applications because the wood is naturally insect resistant and does not need to be treated with dangerous chemicals. Balsa is used for models and lightweight wood projects because it is easy to work with.
When picking out wood for any project, there are a few things that a woodworker should look for, regardless of the wood being used. It should have a tight, even grain without excessive knots or changes in pattern, unless it is being used decoratively. The wood should also not have any cracks or splits, and should be milled along the grain so that it will be strong. Woodworkers should be wary of staining and discoloration, which may represent exposure to water that could result in rot later.