Blue Ash

Blue Ash is a tree, Fraxinus quadrangulata, that is native to the east-central United States, from westernmost Pennsylvania south and west to eastern Oklahoma, and also just into southernmost Ontario in Canada. It is typically found over calcareous substrates such as limestone, growing on dry limestone slopes and in moist valley soils, at elevations of 120–600 m. It is one of a number of ashes 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 typically reach a height of 15–20 m, exceptionally to 40 m tall. They bear small, purplish flowers in the early spring, before the leaves appear. The leaves are 20–30 cm long, with 7–9 (rarely 5 or 11) leaflets. The seeds are 3–4 cm long, including the wing.

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