How to identify ash trees (and EAB risk)
Ash trees (*Fraxinus* spp.) are among the most recognizable and -- currently -- the most threatened trees in North American urban and suburban landscapes. Emerald ash borer (EAB), *Agrilus planipennis*, has killed hundreds of millions of ash trees since its arrival in Michigan around 2002. Per USDA.
Ash trees (Fraxinus spp.) are among the most recognizable and — currently — the most threatened trees in North American urban and suburban landscapes. Emerald ash borer (EAB), Agrilus planipennis, has killed hundreds of millions of ash trees since its arrival in Michigan around 2002. Per USDA Animal and Plant Health Inspection Service (APHIS), EAB has spread to over 35 states and several Canadian provinces and is present in virtually all ash-growing regions of eastern North America.
Knowing how to identify an ash tree — and how to spot EAB damage early — determines whether you can act while management options remain viable.
Genus-level identification
Ash shares the "MAD Cap Horse" opposite-leaf mnemonic (Maple, Ash, Dogwood, Catalpa, Horse-chestnut) — opposite leaves, paired at each node. The combination of:
- Opposite leaf arrangement
- Compound leaves (multiple leaflets per leaf)
immediately narrows to ash, boxelder maple, or elderberry among common eastern trees. Boxelder maple leaflets come in groups of 3–5 and the tree produces maple samaras. Elderberry (Sambucus) is a shrub, rarely a tree. Ash is the most likely identification when a large tree has opposite compound leaves.
Per Penn State Extension, a third separator: ash produces paddle-shaped, single-winged seeds called samaras (not paired like maple samaras), typically in dense hanging clusters.