Knotty pine is not generally used in vital structural applications, because pine is a very soft wood and the knots may cause it to split, break, or bow. For decorative purposes, however, this wood is quite suitable, although it can be overwhelming when used to excess. It is particularly popular in cabins and other rural retreats, and many manufacturers of artificial wood paneling copy the distinctive bulls-eye look of knotty pine. There are over one hundred species of pine across the Northern hemisphere, and a number of species that grow in Southern climates as well. Pine trees are evergreen conifers and highly resinous, which accounts for their distinctive odor. The sap can be made into turpentine and other products, and it is quite difficult to remove from clothing or hair, so most pine used in construction is aged. Most species have scaly, grayish bark and needle-like green leaves. As the trees mature, they grow outward as well as upward, ultimately subsuming branches in their trunks, and this is how knots are formed. The scarred areas around knots are unusable for structural timber, and it’s likely that builders attempting to make use of otherwise nonfunctional wood realized the ornamental properties of knotty pine.
Knotty pine is most commonly used on walls, though it also appears in flooring. Because pine is a soft wood, floors made from it are not advisable unless they are carefully conditioned and varnished to prevent dents, scarring, and other damage.