# Blue Ash (Fraxinus quadrangulata)

> The one ash worth planting: square twigs, limestone-loving roots and real tolerance of emerald ash borer.

Category: Uncommon Yard Trees. Grown from seed by Blue Whale Trees. Web version: https://bluewhaletrees.com/plants/blue-ash/

![Old blue ash (Fraxinus quadrangulata) with a spreading crown in a park](https://bluewhaletrees.com/img/plants/blue-ash-h1610-800.jpg)
*Photo: Mason Brock, Public domain · [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Fraxinus_quadrangulata.JPG)*

## Facts

- Type: Large tree
- Mature height: 50 to 70 ft
- USDA hardiness zones: 4 to 7
- Grows wild in: Rocky ground, dry uplands and rich moist slopes
- Native range: 18 states, north to [Minnesota](https://bluewhaletrees.com/tools/native/index.html.md?state=MN), south to [Georgia](https://bluewhaletrees.com/tools/native/index.html.md?state=GA) and west to [Kansas](https://bluewhaletrees.com/tools/native/index.html.md?state=KS) ([Alabama](https://bluewhaletrees.com/tools/native/index.html.md?state=AL), [Arkansas](https://bluewhaletrees.com/tools/native/index.html.md?state=AR), [Georgia](https://bluewhaletrees.com/tools/native/index.html.md?state=GA), [Illinois](https://bluewhaletrees.com/tools/native/index.html.md?state=IL), [Indiana](https://bluewhaletrees.com/tools/native/index.html.md?state=IN), [Iowa](https://bluewhaletrees.com/tools/native/index.html.md?state=IA), [Kansas](https://bluewhaletrees.com/tools/native/index.html.md?state=KS), [Kentucky](https://bluewhaletrees.com/tools/native/index.html.md?state=KY), [Michigan](https://bluewhaletrees.com/tools/native/index.html.md?state=MI), [Minnesota](https://bluewhaletrees.com/tools/native/index.html.md?state=MN), [Mississippi](https://bluewhaletrees.com/tools/native/index.html.md?state=MS), [Missouri](https://bluewhaletrees.com/tools/native/index.html.md?state=MO), [Ohio](https://bluewhaletrees.com/tools/native/index.html.md?state=OH), [Oklahoma](https://bluewhaletrees.com/tools/native/index.html.md?state=OK), [Tennessee](https://bluewhaletrees.com/tools/native/index.html.md?state=TN), [Virginia](https://bluewhaletrees.com/tools/native/index.html.md?state=VA), [West Virginia](https://bluewhaletrees.com/tools/native/index.html.md?state=WV) and [Wisconsin](https://bluewhaletrees.com/tools/native/index.html.md?state=WI))
- Sun: Full
- Soil moisture: Dry, Average
- Growth rate: Medium
- Flowers: March to April
- Fruit: Winged seeds, June to October
- First crop: About 25 years
- Mature spread: 35 ft
- Traits: Rare, Drought tolerant, Fall color, Street tree
- Sold as: Saplings, Seed

Heights and zones are typical ranges for the species in cultivation; local conditions and seed source shift them.

## Availability

Saplings ship [bare-root](https://bluewhaletrees.com/articles/planting-bare-root-trees-on-arrival/index.html.md) or [in a pot](https://bluewhaletrees.com/articles/a-sapling-in-a-pot/index.html.md), [usually 12 to 18 inches tall](https://bluewhaletrees.com/articles/small-sapling-or-big-transplant/index.html.md), in the dormant season, and their [height and age](https://bluewhaletrees.com/articles/reading-a-nursery-listing/index.html.md) are stated with the price, once available. Live plants ship February to May and October to November. Not priced yet: leave an email on the web page for one email when it is priced, with a code for 10% off the plants in that order, not shipping or tax, or write to captain@bluewhaletrees.com.

## Notes

Blue ash survives emerald ash borer at far higher rates than green or white ash, and in Ohio and Michigan it is often the last ash standing. It is a tree of dry limestone slopes and glades from Ontario to Tennessee, with distinctive four-angled twigs and inner bark that turns blue in water. Plant it as a hedge against losing the genus. Well suited to a lawn shade tree or a street planting on dry, alkaline ground.

## Size, growth and what to expect

Blue ash is a long-lived tree, 150 to 200 years and sometimes 300. One tree in central Kentucky was estimated from core samples to be 405 years old. The oldest tree dated by its rings reached 249. Only a tiny share of trees is ever dated this way, so older ones may exist. Our growth estimator models it as a medium tree at roughly a foot and a half a year, between Iowa State's moderate to fast and Kentucky's moderately slow. A mature tree stands 50 to 70 feet tall with a trunk 18 to 40 inches through, and the crown spreads 25 to 35 feet.

The first seed comes at about 25 years, with a heavy crop every 3 to 4 years. The winged seeds run 1 to 1½ inches long and feed birds and small mammals. Early settlers soaked the inner bark to draw a blue dye for yarn, which gave the tree its name.

It grows wild on rocky bluffs from southern Ontario and Michigan west to Wisconsin and Iowa, and south to West Virginia, Alabama and Oklahoma. It is the North American ash least affected by the emerald ash borer, and it has stood where white and green ash have died.

## How to grow Blue Ash

Blue ash wants full sun and dry to average soil, and unlike most trees it prefers thin, alkaline ground over limestone. It grows an open, rounded crown, so set it 35 feet from the house and out from under wires. Set trees about 50 feet apart.

Plant in the dormant season. Saplings arrive bare-root or potted. Make the hole twice as wide as the root mass and no deeper, keep the root flare visible at grade, and return the soil you dug without amendments. Mulch a ring clear of the trunk. Sow seed outdoors in fall and leave the bed a full winter, or longer, before seedlings show.

Water through the first summer when rain fails. Rabbits and voles chew the thin young bark, so guard the lower stem, and tube or cage against deer until the leader clears six feet. Remove a competing leader in winter and leave the rest alone.

Unlike most ashes, blue ash usually carries male and female parts in each flower, and few trees are only male or female. The wind carries the pollen. Emerald ash borer attacks blue ash like any other ash. What sets it apart is how many mature trees survive and recover, though young trees still need watching. It handles drought, heat and high pH better than white or green ash. Fall color is a clear yellow.

## Sources

- [NC State Extension Gardener Plant Toolbox: Fraxinus quadrangulata](https://plants.ces.ncsu.edu/plants/fraxinus-quadrangulata/)
- [The Morton Arboretum: blue ash](https://mortonarb.org/plant-and-protect/trees-and-plants/blue-ash/)
- [Iowa State University Extension, Natural Resources: blue ash](https://naturalresources.extension.iastate.edu/forestry/iowa_trees/trees/blue_ash.html)
- [University of Kentucky Forestry and Natural Resources: blue ash](https://forestry.mgcafe.uky.edu/common_ky_trees/blue-ash)
- [USDA NRCS PLANTS Database: Fraxinus quadrangulata, FRQU](https://plants.sc.egov.usda.gov/plant-profile/FRQU)
- [USDA Forest Service, Woody Plant Seed Manual (2008), Fraxinus chapter](https://rngr.net/publications/wpsm/genera/f/at_download/file)
- [Missouri Department of Conservation field guide: Ashes](https://mdc.mo.gov/discover-nature/field-guide/ashes)
- [Virginia Tech Dendrology: blue ash, Fraxinus quadrangulata](https://dendro.cnre.vt.edu/dendrology/syllabus/factsheet.cfm?ID=475)
- [Lady Bird Johnson Wildflower Center: Fraxinus quadrangulata](https://www.wildflower.org/plants/result.php?id_plant=FRQU)
- [NatureServe Explorer: Fraxinus quadrangulata](https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.134797/Fraxinus_quadrangulata)
- [Committee on the Status of Endangered Wildlife in Canada (COSEWIC): assessment and status report on the Blue Ash (Fraxinus quadrangulata) in Canada, 2014](https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/cosewic-assessments-status-reports/blue-ash-2014.html)
- [Ontario Ministry of Natural Resources and Forestry: Recovery Strategy for the Blue Ash (Fraxinus quadrangulata) in Ontario, Bickerton 2017](https://www.ontario.ca/page/recovery-strategy-blue-ash)
- [Mathieu and McCullough 2025, Environmental Entomology 54: 603-614, Long-term survival and radial growth of four North American and two Asian ash species in a common garden exposed to emerald ash borer invasion](https://pmc.ncbi.nlm.nih.gov/articles/PMC12202040/)
- [Virginia Tech Dendrology, Eastern OLDLIST of maximum tree ages (Neil Pederson): Fraxinus quadrangulata, blue ash](https://dendro.cnre.vt.edu/olds/detail.cfm?genus=Fraxinus&species=quadrangulata)
- [Castanea: Bryant and others 1980, Castanea 45(3)](https://castaneajournal.com/article/the-blue-ash-oak-savanna-woodland-a-remnant-of-presettlement-vegetation-in-the-inner-bluegrass-of-kentucky/)

## Read before planting

- [Ten planting mistakes that quietly kill trees](https://bluewhaletrees.com/articles/ten-planting-mistakes/index.html.md)
- [Transplanting young trees: timing, water and protection](https://bluewhaletrees.com/articles/transplanting-young-trees/index.html.md)
- [Protecting young trees from voles, rabbits, deer and squirrels](https://bluewhaletrees.com/articles/protecting-trees-from-animals/index.html.md)
- [Native trees for the Southeast: the Carolinas, Georgia, north Florida, Tennessee and Kentucky](https://bluewhaletrees.com/articles/native-trees-for-the-southeast/index.html.md)
- [Winter identification: telling native trees apart by bark, buds and twigs](https://bluewhaletrees.com/articles/winter-tree-identification/index.html.md)
- [Six trees not to plant near a house, and what to plant instead](https://bluewhaletrees.com/articles/trees-not-to-plant-near-a-house/index.html.md)

## Related

- Plants that share its sun and soil: [Northern Red Oak](https://bluewhaletrees.com/plants/northern-red-oak/index.html.md), [Mockernut Hickory](https://bluewhaletrees.com/plants/mockernut-hickory/index.html.md), [Rock Elm](https://bluewhaletrees.com/plants/rock-elm/index.html.md) and [Pignut Hickory](https://bluewhaletrees.com/plants/pignut-hickory/index.html.md)
- Under its canopy: [Mapleleaf Viburnum](https://bluewhaletrees.com/plants/mapleleaf-viburnum/index.html.md), [Alabama Azalea](https://bluewhaletrees.com/plants/alabama-azalea/index.html.md) and [Downy Arrowwood](https://bluewhaletrees.com/plants/downy-arrowwood/index.html.md)
- Same size, similar character: [Cherrybark Oak, Wye Island line](https://bluewhaletrees.com/plants/cherrybark-oak/index.html.md), [Live Oak](https://bluewhaletrees.com/plants/live-oak/index.html.md), [Nutmeg Hickory](https://bluewhaletrees.com/plants/nutmeg-hickory/index.html.md) and [Bur Oak](https://bluewhaletrees.com/plants/bur-oak/index.html.md)
- [Planting-site check](https://bluewhaletrees.com/tools/site-check/index.html.md): for a thrive, struggle or fail verdict on Blue Ash, add ?species=blue-ash with zone (2 to 10), sun (full, part, shade) and moisture (dry, average, wet) to that address; for example, the verdict for zone 4, part sun and average soil as Markdown is at https://bluewhaletrees.com/tools/site-check/index.html.md?species=blue-ash&zone=4&sun=part&moisture=average
- [Companion species for Blue Ash](https://bluewhaletrees.com/tools/companions/index.html.md?species=blue-ash): the natives that share its ground and the plants that pair with it in a yard.
- [Transplant planner](https://bluewhaletrees.com/tools/transplant/index.html.md?species=blue-ash): whether Blue Ash can be moved and what the move takes, the root ball, its weight, who can move it and the months, as Markdown at that address (add caliper= or height=, month= 1 to 12 and soil= sandy, loam or clay)
- [Tree growth estimator](https://bluewhaletrees.com/tools/growth/index.html.md): how the height and trunk projections are made; the estimate for Blue Ash as Markdown is at https://bluewhaletrees.com/tools/growth/index.html.md?species=blue-ash (add height=, years= and site= poor, average or good)
- [Seed sowing planner](https://bluewhaletrees.com/tools/sowing/index.html.md): how Blue Ash is sown, in the chart for every species (treatment, cold days, depth, timing); the dated plan for it as Markdown is at https://bluewhaletrees.com/tools/sowing/index.html.md?species=blue-ash (add state= and zone= for your own frost dates, method=fridge for the refrigerator route)
- [Pollination planner](https://bluewhaletrees.com/tools/pollination/index.html.md): what Blue Ash needs for a crop and how many to plant, in the table for every species; the verdict for 1 of them as Markdown is at https://bluewhaletrees.com/tools/pollination/index.html.md?plants=blue-ash:1
- [Planting-window tool](https://bluewhaletrees.com/tools/planting-window/index.html.md): when to plant Blue Ash where you live, as a fall and a spring window from the local frost dates; the windows as Markdown are at https://bluewhaletrees.com/tools/planting-window/index.html.md?species=blue-ash&state=MO&zone=6 with your own state and zone in place of those
- [Planting-distance tool](https://bluewhaletrees.com/tools/distance/index.html.md): how far Blue Ash goes from a house, a septic field, a walk, wires, a property line and the next tree; the distances as Markdown are at https://bluewhaletrees.com/tools/distance/index.html.md?species=blue-ash&near=house,septic,pavement,wires,boundary,tree
- [Bloom and fruit calendar](https://bluewhaletrees.com/tools/calendar/index.html.md): the months Blue Ash flowers and fruits, in the grid for every species; its own row and the gaps of a planting with it as Markdown at https://bluewhaletrees.com/tools/calendar/index.html.md?plants=blue-ash