Hardwood trees reproduce through seeds containing a covering, while softwood trees reproduce using a naked, uncovered seed. Examples of hardwoods are apple, acorn and hickory trees, whereas softwoods include pine, firs and spruce trees.
Hardwood trees, also known as angiosperms, tend to lose their leaves during colder months. Softwood trees, known as gymnosperms usually keep their leaves year round. Hardwood and softwood trees are also often defined by how difficult they are to cut through, with hardwood trees being denser than softwoods. The softer the wood, the more air it contains. There are exceptions to this secondary definition, however; balsa, one of the least dense woods, is considered a hardwood.
The wood anatomy of hardwoods and softwoods differ as well. Softwood have a simpler anatomy than hardwoods, with a small number of differing cells. Hardwoods are far more complex, with not only a greater number of cell types, but also the addition of large vessels throughout that can be seen by the naked eye as pores.
Hardwoods and softwoods are not limited within individual species, though. The same species of wood can have subspecies of both hard and soft woods within it. For example, while pine trees are softwoods, Southern and Virginia pines are considered hard softwoods, while white and sugar pines are considered soft softwoods.