Blue ash

Blue ash is a tree, Fraxinus quadrangulata, that is native to the eastern United States. It is typically found over calcareous substrates such as limestone, growing on dry limestone slopes and in moist valley soils, at elevations of 400-2000 feet. It is one of a number of ash trees native to North America.

Blue ash has the distinctive feature that the twigs typically have four corky ridges, giving them a square appearance (in cross-section), hence the species name, quadrangulata, meaning four-angled. The trees reach a height of 70 feet (21 meters). They bear small, purplish flowers in the early spring, before the leaves appear.

The common name is due to the fact that early European settlers made blue dye from the inner bark.