Green Ash

Fraxinus pennsylvanicaUSDA 3a–9a

Updated 2026-10-18 · Species & health

Mature height60–70 ft
Mature DBHNot published
Canopy spread45–50 ft
Growth rateFast
Firewood20.0–23.0 MBTU / cord

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

Feature	Ash	Commonly confused with
Branching	Strictly opposite	Maple (also opposite) — check the leaf
Leaf	Compound, 5–9 leaflets	Walnut (more leaflets, aromatic)
Bark	Diamond-patterned ridges on mature stems	Elm (interlacing, layered in section)
Seed	Single winged samara, hanging in clusters	Maple'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; Iowa State extension draws the line at canopy thinning: under about half thin, treatment is still worth weighing; past that, the tree is on a declining curve 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.

Green ash is good firewood at 20.0 to 23.0 million BTU per cord on the Illinois and Utah State extension tables, and it has less water to lose than oak, so it is usually ready well before an oak split is. Do not move it out of the county — the BTU chart carries the numbers and the warning.

Sources

UF/IFAS Extension ST266 — Fraxinus pennsylvanica, green ash: height 60–70 ft, spread 45–50 ft, zones 3A–9A, fast growthretrieved 2026-10-18
Iowa State University Extension — Emerald ash borer: treat trees with less than 50% canopy thinning; retreat every 1–2 years by productretrieved 2026-10-18
University of Illinois Extension — Firewood: burning safety (million BTU per cord)retrieved 2026-10-18
Utah State University Extension — Wood Heating, Table 1 (heat per cord of dry wood)retrieved 2026-10-18
BLS OEWS May 2025 · 37-3013 · hourly mean $26.91 (the crew rate behind injection and removal)retrieved 2026-09-04