Ash trees belong to the species Fraxinus and have two characteristics in common across all the varieties: opposing branches and compound leaves. The trees of this species are deciduous with dark green leaves and nutlet seeds enclosed in winglike cases called samaras. More than 65 types of ash tree can be found in North America though only five or six are most common.
The most commonly found ash trees are the European, green, black, blue and white ash. The European ash, also called the common ash, is known scientifically as Fraxinus excelsior. It is native to Europe and Asia. White ash (Fraxinus americana) gets its name from the color of the underside of its leaves. Blue ash (Fraxinus quadrangulata) is common in the Midwestern United States. Green ash (Fraxinus pennsylvanica) is sometimes grouped in the white ash family as it has similar qualities. Black ash (Fraxinus nigra) is more common from Illinois north and throughout Canada.
The wood of ash trees in general is flexible, making it useful for a wide variety of items. The white ash is especially desirable because of the toughness and elasticity of its wood. White ash wood is white in color and is known for its resonance quality. European and other ashes vary from a creamy white to light brown.
Blue ash bark was used by early European settlers to make blue dye, giving the tree its common name. Because of its resonance, the wood from black ash is often used to make guitars and basses in addition to baskets. White, European and other ashes are used to make tool handles, athletic equipment such as baseball bats and racquet handles and furniture. All ash trees make excellent shade and street trees.
Ash species vary in size dramatically with the blue and green ashes being at the smaller end of the scale. Blue ashes average 40 feet in height with a 30-foot spread while green ashes reach 50 to 60 feet tall and can span only 20 to 30 feet typically. The white and European ashes are much larger. European ashes soar to 75 feet tall and spread to 70 feet wide. The white ash, under proper conditions, can tower at 80 feet with a spread of 40 to 80 feet.
Most ash trees average a lifespan of about 70 years, making them a good choice for shade or street trees. Most are tolerant of a wide range of soil conditions except for the white ash, which does not like clay soil. All prefer full sun and all are susceptible to the emerald ash borer, a destructive beetle that can kill an ash within two years.