If you were to stroll through the lumber department of your local lumberyard or home center, you'll find that probably 90% of the wood materials available will be softwoods (or products manufactured from softwoods), with the remaining 10% being hardwood varieties. Why the disparity? Softwoods are inexpensive and readily available in the United States and Europe and are well suited for general projects, but that doesn't necessarily make them good woodworking materials.
What are softwoods?
The term "softwood" actually refers to a group of different species of trees from which the wood is harvested. A general rule of thumb is that softwoods come from coniferous, or "evergreen" trees, where hardwoods typically come from deciduous, or leafy trees. This can be a bit deceiving, as the softest wood available, balsa wood, would be considered soft and extremely lightweight, but is technically a hardwood.
Softwood (conifer) forests are found primarily in the northern hemisphere. The greatest concentration in North America is found in the northwestern United States and Canada, although there is also a concentration found in the southeastern US. Conifers are fast-growing, can be easily cultivated, and produce relatively straight trunks, which makes harvesting and processing much less expensive. Conifers are also used in the manufacture of fiberboard and paper. These trees grow so tall and straight, with a relatively minimal taper along the length of the trunk, so this type of tree has been used for centuries for log cabin construction.
Typical Softwood Species
In most home centers, you'll find two predominant types of softwood lumber: SPF, and (yellow) pine. SPF is an acronym that stands for spruce, (white) pine and (Douglas) fir. Lumber in a stack that is marked as SPF could be any of these three species, or perhaps contain pieces of all three within the same stack. All three species are similar in appearance, being quite light in color with growth rings that are typically rather widely spaced.
While SPF makes up the great majority of softwoods sold in the United States today, depending on your location, you likely will often find other varieties such as yellow pine. As one might expect, yellow pine has a much more yellow color, which may affect your choices of finish should you choose to utilize this type of material. Yellow pine tends to be a bit more temperamental, at least in terms of stability, than the standard spruce, pine, or fir species.
When to Use Softwoods
No matter which types of softwoods you choose to use in your projects, keep in mind that most softwoods are developed for construction uses, and not necessarily for building furniture. Remember that softwoods need to become acclimated to the environment in which the finished project will reside before beginning woodworking to avoid excessive movement after the project is completed.
These softwoods are often shipped very wet, with limited drying time, and need to have time to reduce their moisture content. Even after considerable drying time, these species can contain a considerable amount of sap, which sticks to blades and bits as pitch. This pitch can heat up a blade or a bit and cause burning of both the bit and the wood as it is being cut.
Woodworking with softwood lumber can be a fine choice when building utilitarian projects (cabinets for the woodshop, painted projects, dog houses, etc.), but should probably be avoided when you intend to use stain for the finish or want to use the completed piece to be employed inside the house.