Hardwood sources are trees that are used to make furniture, flooring, and other wood products. The four most common hardwood sources are OAKS, elms, ash trees, and oak trees. OAKS are deciduous trees that can be found in temperate climates around the world. Elms are also deciduous trees that are native to Europe, Asia, and North America. Ash trees are a type of flowering tree that is native to Europe, Asia, and North America. Oak trees are a type of deciduous tree that is native to North America, Europe, and parts of Asia.