The 2 Common North American Ash Trees

Two Common Ash Trees in the Olive Family

Fraxinus pennsylvanica (Green ash or Red a...
A Green Ash Tree. James Young/Dorling Kindersley/Getty Images

An ash tree commonly refers to trees of the genus Fraxinus (from Latin "ash tree") in the olive family Oleaceae. The ashes are usually medium to large trees, mostly deciduous though a few subtropical species are evergreen.

Identification of ash during the spring/early summer growing season is straight forward. Their leaves are opposite (rarely in whorls of three) and mostly pinnately compound but can be simple in a few species.

The seeds, popularly known as keys or helicopter seeds, are a type of fruit known as a samara. The genus Fraxinus contains 45-65 species worldwide.

The Common North American Ash Species

Green and white ash trees are the two most common ash species and their range covers most of the Eastern United States and Canada. Other significant ash trees to cover significant ranges are black ash, Carolina ash, and blue ash.

  • green ash
  • white ash

Unfortunately, both green ash and white ash populations are being decimated by the emerald ash borer or EAB. Discovered in 2002 near Detroit, MIichigan, the boring beetle has spread through much of the northern ash range and threatens billions of ash trees.

Dormant Identification

Ash has shield-shaped leaf scars (at the point where the leaf breaks away from the twig). The tree has tall, pointed buds above the leaf scars. There are no stipules on ash trees so no stipulate scars.

The tree in winter has pitchfork-like looking limb tips and there could be long and narrow clustered winged seed or samaras. Ash has continuous bundle scars inside leaf scar looks like "smiley face".

Important: A leaf scar is the major botanical feature when keying a green or white ash. The white ash will have a U-shaped leaf scar with the bud inside the dip; the green ash will have a D-shaped leaf scar with the bud sitting atop the scar.

Leaves: opposite , pinnately compound , without teeth.
Bark: gray and furrowed.
Fruit: a single winged key hanging in clusters.

The Most Common North American Hardwood List

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Nix, Steve. "The 2 Common North American Ash Trees." ThoughtCo, Aug. 6, 2016, thoughtco.com/common-north-american-ash-trees-1341846. Nix, Steve. (2016, August 6). The 2 Common North American Ash Trees. Retrieved from https://www.thoughtco.com/common-north-american-ash-trees-1341846 Nix, Steve. "The 2 Common North American Ash Trees." ThoughtCo. https://www.thoughtco.com/common-north-american-ash-trees-1341846 (accessed November 22, 2017).