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Green Ash

Fraxinus pennsylvanica

Updated 2026-09-04

Woodcut of a mature ash tree
An upright vase crown with strictly opposite branching — the identification, and the tree the borer changed.
Green ash was planted everywhere for a generation because it grows fast, tolerates city conditions and asks for nothing. Emerald ash borer turned that ubiquity into the second great North American street-tree loss, and every decision about an ash today runs through that one fact.

Identifying it in ten seconds

FeatureAshCommonly confused with
BranchingStrictly oppositeMaple (also opposite) — check the leaf
LeafCompound, 5–9 leafletsWalnut (more leaflets, aromatic)
BarkDiamond-patterned ridges on mature stemsElm (interlacing, layered in section)
SeedSingle winged samara, hanging in clustersMaple's paired samara

Sound

Opposite branching plus a compound leaf plus diamond bark is ash, and almost nothing else in a North American street. Getting this right matters because the treatment decision is species-specific.

The one decision

Treat or remove, and the canopy answers it. A full-canopied ash worth keeping justifies a repeating trunk-injection programme; an ash more than about a third thin is on a declining curve that treatment rarely reverses. The threshold table is in the EAB guide.

Watch

Deferring the decision is itself a decision, and an expensive one — because of what happens to the wood.

Why a dead ash gets expensive fast

Ash killed by the borer goes brittle unusually quickly. Within a couple of years the limbs will not hold a climber and the wood fails without warning under rigging loads. The job moves from a climbing removal to a crane or lift removal, which is a materially larger invoice for the same tree.

Price the standing job now in the removal calculator and compare it against three more years of treatment. That is the arithmetic, and it usually favours acting.

After the ash

The lesson of both the elm era and the ash era is monoculture. Replant a mix — the mature dimensions of the alternatives are on oak and maple, and the elm story is in Dutch elm disease.

Ash is excellent firewood with an unusual advantage: low green moisture, so it seasons in about nine months rather than two years. Do not move it out of the county — the BTU chart carries the numbers and the warning.

Sources

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