- A tree is composed of both heartwood and sapwood. Heart pine is the heartwood of the longleaf pine tree. Because of properties particular to this species of pine, Heart Pine is extremely hard, strong, and stable, making it an excellent wood for flooring. While there is no uniformity in how these terms are used, a good way to determine what type of pine flooring you are looking at is to determine its source. Newly harvested pine floors are most likely to be Yellow Pine, while pine floors recycled from turn-of-the-century mills or sourced from river bottoms are most likely to be Old Growth Heart Pine.