Green/White Ash

Problem Species

Upper Midwest

308 cities

Green ash (Fraxinus pennsylvanica) and white ash (Fraxinus americana) are large deciduous trees identifiable by their opposite compound leaves with 5 to 9 leaflets and distinctive diamond-furrowed bark on mature trunks. White ash leaflets have a noticeably pale, almost white underside; green ash leaflets are glossier and narrower. Both were planted heavily across Upper Midwest streets and yards from the 1960s through the 1990s, sometimes accounting for 20 to 30 percent of a city's entire tree canopy. That overplanting is a big reason Emerald Ash Borer has been so devastating here.

Lifespan

Both species can live 200 or more years under natural conditions. In Upper Midwest urban landscapes today, untreated ash have an effective lifespan measured in years, not decades.

Mature Size

Typically 50 to 80 feet tall with a canopy spread of 40 to 50 feet, though street-planted trees are often smaller due to soil compaction and root restriction.

⚠ Problem Species

Why it's a problem: Functionally extinct in urban landscapes due to Emerald Ash Borer

Care & Maintenance

Before you spend money on fertilizing or watering an ash, get it assessed for Emerald Ash Borer. Both species prefer full sun and tolerate the clay-heavy soils common across the Upper Midwest, which made them popular street trees. If you have a confirmed healthy ash and are already on a treatment program, deep watering during drought stress can slow overall decline.

Common Issues & Threats

Emerald Ash Borer (Agrilus planipennis): This invasive Asian beetle has killed hundreds of millions of ash trees across North America. Larvae cut S-shaped galleries beneath the bark, blocking water and nutrient flow. You will see D-shaped exit holes about 1/8 inch wide, heavy woodpecker activity stripping bark off upper limbs, and dieback starting at the crown top. Here is what most people get wrong: by the time those symptoms are obvious, the tree is often already more than 50 percent infested and well past the point where treatment makes financial sense.
Ash Anthracnose: A fungal disease that causes brown, irregular blotches on leaves during cool, wet springs. It looks alarming but is rarely fatal on its own. Trees typically releaf by midsummer and do not need treatment unless they are already weakened by EAB.
Verticillium Wilt: A soil-borne fungal infection that blocks the tree's water-conducting tissue, causing branch dieback and wilting even when the soil is moist. There is no cure. Infected trees should be removed and the wood disposed of off-site, not chipped into mulch used around other trees.

Pruning Guide

If you prune ash, do it between October and March when EAB adults are not flying. Adults are active roughly June through August, and fresh pruning cuts can attract them to a tree that might otherwise go undetected longer. If the tree is already in an EAB-affected area and not on a treatment program, structural pruning is rarely worth the investment.

Did You Know?

White ash wood is exceptionally strong and flexible, which is why it was the wood of choice for Major League Baseball bats for most of the 20th century. It is also worth knowing that moving ash firewood is one of the primary ways EAB spreads to new areas, so if you have a dead ash taken down, do not transport the wood outside your immediate area.

Where Green/White Ash Is Found

Green/White Ash is common in 308 of the US communities we cover, across 1 climate regions.

Hardiness Zones 2-8

Eden Prairie, MN Zone 5a Oak Park, IL Zone 6a Wheaton, IL Zone 5b Minnetonka, MN Zone 5a Edina, MN Zone 5a Downers Grove, IL Zone 5b Chesterfield, MO Zone 6b Dublin, OH Zone 6b Glenview, IL Zone 6a Elmhurst, IL Zone 6a Park Ridge, IL Zone 6a Upper Arlington, OH Zone 6b

... and 296 more cities

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