Fraxinus excelsior (Ash; also European Ash or Common Ash on occasion to distinguish it from other ash species), a tall, handsome tree, common in Britain, is readily distinguished by its light-grey bark and by its large compound leaves, divided into four to eight pairs of lance-shaped leaflets, tipped by a single one, an arrangement which imparts a light feathery arrangement to the foliage. The leaflets have sharply-toothed margins and are about 3 inches long.

Ash bark has been employed as a bitter tonic and astringent, and is said to be valuable as an antiperiodic. On account of its astringency, it has been used, in decoction, extensively in the treatment of intermittent fever and ague, as a substitute for Peruvian bark. The decoction is odourless, though its taste is fairly bitter. It has been considered useful to remove obstructions of the liver and spleen, and in rheumatism of an arthritic nature.