Blue Ash - Fraxinus quadrangulata
This medium-sized ash (75 feet) is adapted to limestone substrates, achieving its greatest size in southern Illinois and the Great Smoky Mountains. The common name is derived from the sap, which turns blue when exposed. The trunk is tall in closed forest. The branches are curved, rather like an oak, and the twigs are 4-sided--hence the scientific name quadrangulata. The leaf is up to 12 inches in length, and the many leaflets are toothed on the margins. Historically, a blue dye was extracted from the inner bark and used for cloth.