Ash Trees in 2026: How to Tell White, Green, Black and Blue Ash Apart, Where the Borer Stands, and 5 Trees to Plant Instead

An ash has branches and leaves that grow in opposite pairs, and each leaf is divided into leaflets (the Nebraska Forest Service counts 5 to 11 on an ash). Pass both tests and the common candidates are ash, boxelder, buckeye and horse chestnut. Twig color, leaflet arrangement and fruit settle which. Among the ashes, white, green, black and blue then separate on leaf-scar shape, whether the side leaflets have stalks, twigs, bark and seed, and the table below compares them.

The bigger question is what to do with one. Emerald ash borer attacks all five ash species native to the region USDA Forest Service scientist Kathleen Knight summarized in 2014 (white, green, black, pumpkin and blue), and she writes that nearly 100% of attacked trees eventually die (her text cites one study that disagrees); NC State says blue ash seems to be the least affected. NC State Extension’s white and green ash pages say planting new ash trees is no longer recommended. Below you will find real cost ranges for treating versus removing a tree you already own, and five trees to plant instead, with Iowa State’s USDA zone ranges.

Is It an Ash? The MAD Horse Buck Test and Its Look-Alikes

Opposite branching plus a compound leaf is the two-step test for ash. A University of Maryland Extension blog post passes on the mnemonic “MAD Horse Buck” for trees with opposite leaves: maple, ash, dogwood, horse chestnut and buckeye. The table below lists Ohio buckeye and horse chestnut. Pumpkin ash, one of the five native species Knight lists, is outside this guide, which covers four species. Michigan State University Extension defines opposite as leaves and branches growing directly across from each other, rather than staggered along the stem.

Step two is the leaf. A compound leaf is one leaf with several leaflets attached to a single leaf stem, and the Nebraska Forest Service counts 5 to 11 leaflets on an ash leaf. Black walnut and mountain-ash also have compound leaves, but their branches are alternate, so they drop out at step one. Boxelder is the one that fools people, because it is a maple with an ash-like leaf. The table sorts out the trees that pass one or both steps.

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In short: opposite twigs, a leaf with several leaflets along one central stem and gray-to-brown twigs with no waxy coating point to ash. Boxelder usually shows 3 to 5 leaflets, so 5 is where the counts overlap, and the tie-breakers are its green to purplish-brown twigs, often with a waxy white coating, and its paired winged seeds. Leaflets that fan out from one point mean a buckeye or horse chestnut, not ash.

Maples have their own sorting rules, which our guide to types of maple trees covers by leaf edge, bud and seed.

White, Green, Black and Blue Ash: The Field Marks That Separate Them

The fastest single check on a leafy branch is the leaflet stalk: stalkless side leaflets mean black ash, and four-angled corky twigs mean blue ash. White versus green is the harder split, and it comes down to the leaf scar, the underside of the leaflets and the seed.

Sources for each cell are Virginia Tech’s dendrology fact sheets, the USDA Agricultural Research Service ash key and NC State Extension’s plant toolbox, and they disagree in small ways. Leaflet counts differ a little between sources, so treat them as ranges.

No Leaves, No Seeds? Use the Leaf Scar

In winter the leaf scar is the clue left on a bare twig. MSU Extension describes the white ash scar as a letter C turned on its side and the green ash scar as a D turned on its side. Seeds are the weaker clue for two reasons. MSU says many ash cultivars are seedless, and Virginia Tech notes that white and green ash are dioecious (separate male and female trees), so a male tree never shows seeds either.

If the tree came from a nursery, the cultivar name points to the species. The Nebraska Forest Service lists ‘Marshall’s Seedless’ and ‘Patmore’ among common green ash cultivars and ‘Autumn Purple’ among white ash cultivars.

What Emerald Ash Borer Has Done: Where It Stands and How It Spread

Knight reports that emerald ash borer attacks all five ash species native to the region she studied and that nearly 100% of attacked trees eventually die (her text cites one study that disagrees), and the main hint of an exception is blue ash, which NC State says seems to be the least affected. The beetle was first detected in North America in 2002 in southeast Michigan, according to USDA APHIS, and Knight dates its arrival to the mid-1990s near Detroit.

How the Borer Kills, and How Fast

The larvae feed under the bark. Their galleries injure the phloem and xylem, the tissues that carry nutrients and water, and large branches or even the trunk can be girdled, according to a 2009 Michigan State University Extension bulletin on insecticide options. NC State Extension says the beetle typically kills an ash within 3 to 5 years of infestation. In the Forest Service’s Ohio monitoring sites it can take 3 to 6 years for a stand to go from healthy to nearly complete mortality, and most plots around Toledo passed 95% mortality by 2009. NC State’s 3 to 5 years is for a single tree, while the Ohio figure covers whole stands. Dead ash do not stand long: over 80% of dead trees in those Ohio sites fell within 5 years of death.

Species-level numbers are thin, so here is what the sources we could open say about each one.

To check a tree you already own, our guide to ash bark blonding and borer signs walks through the woodpecker check that shows up before canopy dieback does.

Where It Has Been Found

The count keeps moving. The 2009 edition of a Michigan State University Extension bulletin counted 12 states and two Canadian provinces with known infestations. Nebraska, in June 2016, was the 27th state to confirm it, according to the USDA National Invasive Species Information Center. APHIS’s EAB page now says infestations have been detected in 38 states and the District of Columbia. Washington’s first detection was found in Vancouver on August 3, 2026, per Washington State University Tree Health, so the 38 may or may not include it; check APHIS for the current count.

The table lists selected first detections from the federal invasive-species center’s page, plus Washington. Each row is that state’s own first reported detection, with dates as precise as the source gives them.

Where you live sets the clock. University of Wisconsin Extension reports that every Wisconsin county now has confirmed detections. APHIS removed its domestic EAB quarantine regulations in 2020, effective January 14, 2021, and an entry on the center’s page, from a New York clearinghouse, says the spread was most likely due to the transport of infested firewood, ash nursery stock and unprocessed ash logs. APHIS also rears and releases stingless wasps as biological control agents.

Lingering Ash: The 0.05% and What the Research Can and Cannot Promise

Lingering ash are trees that stay alive with healthy crowns after the borer has killed most ash in their stands, and they are rare. In a USDA Forest Service report, Jeanne Romero-Severson and Jennifer Koch put the share at about 0.05% of green ash.

Survival is not immunity. Romero-Severson and Koch report that individual trees use different defense types, and that these defenses extend survival but do not prevent premature death. Simple backcrossing from borer-resistant Asian ash will not transfer resistance to green ash, so they expect that combining the defenses of different native survivors through breeding could yield offspring that resist the borer better than their parents.

A 2026 Forest Service paper in New Forests by Mary Mason and colleagues tests whether that is possible. It grafted lingering trees and screened them in greenhouse bioassays for larvae killed by the tree’s defenses and larval weight. Clonal repeatability for the share of larvae killed, which the authors use to estimate heritability (higher means more of the difference between trees comes from their genes, not a percentage of resistance), was 0.15 for green ash selections, 0.45 for white ash selections and 0.87 for one green ash family with lingering-ash parentage. The authors call a genetic basis “the essential requirement for an EAB resistance breeding program.”

Cornell’s November 2025 update describes 139 grafted trees from 26 lingering-ash parents in three conservation banks, with a goal of 50 to 60 parents and resistance testing of the cloned trees within the decade. Neither the 2026 paper’s abstract nor Cornell’s update says that resistant trees are available to buy.

Treat or Remove? The Cost Arithmetic for an Ash You Already Own

Treat a healthy ash you value as early as you can, because less canopy thinning means better odds. The sources give these thresholds: Colorado State says trees thinned up to 30% can usually recover with a program of emamectin benzoate trunk injections, and trees with about 60 to 70% crown loss are beyond recovery with insecticides. University of Wisconsin Extension advises treating high-value trees, says research suggests treatment is significantly more effective under 50% canopy thinning, and says trees above 50% should be removed. Neither gives a recovery rate for the band from 30% to 50%, so for that band we would ask an arborist, though Wisconsin still favors treatment under 50%. Wisconsin’s removal line (50%) sits below Colorado State’s beyond-recovery range (60 to 70%), and we would follow the stricter 50% line and remove a tree you would not pay to keep.

The reason timing matters is mechanical. Most borer insecticides are systemic, so the tree has to carry the chemical up the trunk and into the canopy, and the larval galleries injure the same vascular tissues that would carry it, as the Michigan State bulletin explains. The bulletin says a tree that has lost more than half its canopy is probably too late to save.

The trunk-injection treatment uses emamectin benzoate, and Colorado State says professional application is required. Colorado State says it can very reliably control the borer for two years, and that increasing evidence indicates it may usually be effective at three-year intervals. Wisconsin’s guidance is every other year. Illinois Extension notes the product is often marketed as needing an injection every two years, while a Michigan State study found a healthy ash typically needs one every three.

Here is our arithmetic, using Illinois’s 2019 range and assuming it is the cost of one injection, which the source does not spell out. Over 10 years, injecting every 2 years means 5 injections: $500 to $1,000. Injecting every 3 years means 4 injections: $400 to $800, if your arborist agrees with the longer interval. Wisconsin’s 2026 “often $200 or more” covers any arborist method, so it is not used in these totals, and current quotes may be higher than the 2019 range. The soil drench in the table is a separate option, priced there for a tree about 10 in. across. Removal is a one-time cost of several hundred dollars to $1,000 or more, while Illinois Extension says that, as far as is known, ash will need treatment for their entire lives. The trade is cost against shade: treatment keeps the tree you have while a replacement grows, and removal ends the bill but also ends the shade.

Doing nothing does not avoid the removal bill; it delays it while the tree declines. Illinois Extension considers ash in a county with confirmed EAB to have a 98% mortality rate unless treated, close to Knight’s figure for attacked trees, though Illinois counts ash in a county with confirmed EAB, and dead ash turn brittle quickly. Wisconsin says removing a recently killed tree while it is still structurally sound can be safer and more cost effective. Prices here are published figures, and the Illinois numbers date from 2019, so get a current local quote before deciding.

Should You Plant an Ash in 2026? The Verdict and 5 Trees to Plant Instead

No. NC State Extension’s pages for both white and green ash say planting new ash trees is no longer recommended because of the borer, and Knight reports that the borer attacks all five ash species native to the region she studied. We found no separate planting guidance for black or blue ash, but the same reasoning applies because the borer attacks them too. Even blue ash, which NC State says seems to be the least affected, “has also suffered from the emerald ash borer.” The reasons are in the sections above: Romero-Severson and Koch put lingering green ash at only about 0.05% and say even their defenses extend survival without preventing premature death, and neither the 2026 breeding paper’s abstract nor Cornell’s update says that resistant trees are available to buy. A large planted ash would also eventually become a removal job, which Wisconsin Extension prices at $1,000 or more for larger trees.

Replace with variety, not one favorite. Iowa State Extension’s rule is that no more than 10% of the trees in your yard and neighborhood should be the same species, no more than 20% the same genus and no more than 30% the same family. It also warns that maple and oak tend to be over-represented in residential neighborhoods, and the Nebraska Statewide Arboretum calls ‘Autumn Blaze’ maple an overplanted silver-maple hybrid to use sparingly. The five trees below come from five different genera and families, and since Iowa State’s warning covers oaks, choose the swamp white oak only if your street is not already full of oaks. Match each tree to its site.

Zones in this replacement table come from Iowa State’s list. NC State’s plant toolbox shows slightly different edges, such as hackberry from zone 3, ginkgo to zone 9 and swamp white oak from zone 4 to 8, so treat the ends of each range as approximate and check a local extension office for your site. Our oak tree leaf identification guide helps you pick the right oak at the nursery.

Ash is deciduous, so if the tree also gave you a windbreak or screen, an evergreen is the missing piece. Our comparison of spruce tree types covers seven spruces by size, zones and disease risk.

Frequently Asked Questions

How do you tell a white ash from a green ash?

Start with the leaf scar and the leaflet undersides. A white ash leaf scar is round at the bottom and notched at the top, while a green ash scar is semicircular to flat across the top. Leaflets are strongly whitened beneath on white ash and green or rusty beneath on green ash. Check the seed only if the tree has fruit, because not every ash tree produces seed: white ash seeds have a full, rounded seed cavity and green ash seeds a slender, thin one.

Can I save an ash tree that already has emerald ash borer?

Sometimes, if thinning is low. Colorado State Extension says trees thinned up to 30% can usually recover with emamectin benzoate trunk injections, and University of Wisconsin Extension says research suggests treatment is significantly more effective under 50% thinning and recommends removal above that, while Colorado State puts crown loss of about 60 to 70% beyond recovery. For the band between 30% and 50%, ask an arborist, though Wisconsin still favors treatment under 50%. Emamectin benzoate injections repeat every two years, or every three if your arborist agrees, and Illinois Extension says that, as far as is known, ash trees will need treatment for their entire lives.

How long does an ash tree live after emerald ash borer arrives?

It depends on what you count. NC State Extension says the borer typically kills an individual ash within 3 to 5 years of infestation. In Forest Service monitoring sites in Ohio, a single stand can take 3 to 6 years to go from healthy to nearly complete mortality, and the Forest Service’s “Saving green ash” report says larvae can kill 100% of the green ash in a stand within 4 to 6 years of the first detection (a green ash stand, from first detection to full loss), with the 0.05% of green ash that survive as lingering trees the exception.

Should I plant an ash tree in 2026?

No. NC State Extension’s white and green ash pages say planting new ash trees is no longer recommended, Knight reports that the borer attacks all five ash species native to the region she studied (we found no separate planting guidance for black or blue ash), and neither the 2026 breeding paper’s abstract nor Cornell’s update says that resistant trees are available to buy. Pick one of the five replacements above (choose the swamp white oak only if your street is not already full of oaks) and keep within Iowa State’s 10-20-30 diversity rule.

Sources

1. USDA APHIS. Emerald Ash Borer. Animal and Plant Health Inspection Service
2. USDA National Invasive Species Information Center. Emerald Ash Borer
3. Washington State University Tree Health. Emerald ash borer detected in Washington State. August 19, 2026
4. Herms DA, McCullough DG, Smitley DR, Sadof CS, Williamson RC, Nixon PL. Insecticide Options for Protecting Ash Trees from Emerald Ash Borer (2009 edition). Michigan State University Extension Bulletin E-3075
5. Knight KS. Outlook for Ash in Your Forest: Results of Emerald Ash Borer Research and Implications for Management. The Woodland Steward, Spring 2014. USDA Forest Service Northern Research Station
6. Romero-Severson J, Koch J. Saving green ash. In: Gene conservation of tree species: banking on the future, General Technical Report PNW-GTR-963, pp. 102-110. USDA Forest Service, 2017
7. Mason ME, Carey D, Romero-Severson J, Knight K, Poland TM, Koch J. Select genotypes of white and green ash show heritable, elevated resistance to emerald ash borer. New Forests 57(1):12, 2026
8. Ramanujan K. Cornell ash trees aim to beat back borer insects. Cornell Chronicle, November 20, 2025
9. University of Maryland Extension. My Winter Native Tree ID Advanced MG Training Experience with Sara Tangren. Maryland Grows, December 15, 2017
10. Brown-Rytlewski D, Thompson R. Distinguishing Ash from Other Common Trees (2003, archive copy). Michigan State University Extension Bulletin E-2892
11. Morris J. Ash Tree Identification Guide (FH24-2015). Nebraska Forest Service, University of Nebraska-Lincoln
12. USDA Agricultural Research Service. Identifying Ash. NPGS Ash Conservation Project
13. Virginia Tech Dendrology. White ash (Fraxinus americana). Fact sheet
14. Virginia Tech Dendrology. Green ash (Fraxinus pennsylvanica). Fact sheet
15. Virginia Tech Dendrology. Black ash (Fraxinus nigra). Fact sheet
16. NC State Extension. Fraxinus americana (white ash). Extension Gardener Plant Toolbox
17. NC State Extension. Fraxinus pennsylvanica (green ash). Extension Gardener Plant Toolbox
18. NC State Extension. Fraxinus nigra (black ash). Extension Gardener Plant Toolbox
19. NC State Extension. Fraxinus quadrangulata (blue ash). Extension Gardener Plant Toolbox
20. NC State Extension. Aesculus glabra (Ohio buckeye). Extension Gardener Plant Toolbox
21. NC State Extension. Aesculus hippocastanum (horse chestnut). Extension Gardener Plant Toolbox
22. Liesch PJ. Is My Ash Tree Worth Treating for Emerald Ash Borer? University of Wisconsin-Madison Extension, revised January 29, 2026
23. University of Illinois Extension. Enjoying the Final Hurrahs of a Staple Landscape Tree. Good Growing, September 10, 2019
24. Cranshaw WS. Insecticides Used to Control Emerald Ash Borer on Residential Shade Trees. Colorado State University Extension, May 2020, reviewed August 2025
25. Iowa State University Extension. What can I plant to replace an ash tree killed by emerald ash borer? Yard and Garden
26. Nebraska Statewide Arboretum. Best Trees to Replace Ash. University of Nebraska-Lincoln
27. NC State Extension. Quercus bicolor (swamp white oak). Extension Gardener Plant Toolbox
28. NC State Extension. Gymnocladus dioicus (Kentucky coffeetree). Extension Gardener Plant Toolbox
29. NC State Extension. Celtis occidentalis (hackberry). Extension Gardener Plant Toolbox
30. NC State Extension. Taxodium distichum (bald cypress). Extension Gardener Plant Toolbox
31. NC State Extension. Ginkgo biloba (ginkgo). Extension Gardener Plant Toolbox