Blue ash Fraxinus quadrangulata

Blue ash is a deciduous tree native to the midwestern U.S.A. in the Oleaceae (olive) family. This tree will grow 50-60 feet tall with an oval to pyramidal form. It has the typical compound leaves of other ash trees but the new stems are 4 sided making it easy to identify. The name quadrangulata actually means four-sided. The common name of blue ash comes from a dye that was extracted from the bark and used to color yarn by the early settlers. This tree has also suffered from the emerald ash borer but seems to be the least affected in comparison to other North American ash trees.

Blue ash is found growing in both damp and dry conditions and tolerates growing on limestone substrates better than other ash trees. It prefers full sun and is not picky about pH or soil types. Unlike some ash trees, blue ash dislikes flooded conditions and tolerates alkaline soils better.

Insects, Diseases, and Other Plant Problems: Emerald ash borer. It can be more difficult to propagate and slower to establish than other ash trees. See potential insect and disease problem factsheets to the left

VIDEO created by Grant L. Thompson for “Trees, Shrubs, and Woody Vines for Landscaping” a plant identification course offered by the Department of Horticulture at Iowa State University.