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Blue Ash (Fraxinus quadrangulata)

Life history

Species overview

Blue Ash (Fraxinus quadrangulata), a Wisconsin Threatened plant, is found in rich upland hardwoods, often with dolomite near the surface. Blooming occurs throughout June; fruiting occurs early July through late August. This species can be identified year-round.

Synonyms: None


  • Distinguishing characteristics: Twigs sharply 4-angled; leaves pinnately compound.
  • Flower characteristics: Flowers small, borne in clusters.
  • Fruit characteristics: Winged samara, flat, elliptic or oblong, 2.5 to 4 cm x 6 to 10 cm; the wing extends almost all the way from the base to the tip and is usually notched at the top.
  • Leaf characteristics: Opposite, pinnately compound with 7 to 11 lance-shaped leaflets, slightly asymmetric at the base and concavely narrowing to a sharp point at the tip.


  • Blooming phenology: throughout June
  • Fruiting phenology: early July through late August
  • Optimum time to identify: This species can be identified year-round


  • Growth form: Tree
  • Vegetative reproduction:
  • Life cycle: Perennial
  • Comments: Associated Species: Acer saccharum, Tilia americana, Juglans nigra.

State status

Status and Natural Heritage Inventory documented occurrences in Wisconsin

The table below provides information about the protected status - state and federal - and the rank (S and G Ranks) for Blue Ash (Fraxinus quadrangulata). See the Working List Key for more information about abbreviations. Counties shaded blue have documented occurrences for this species in the Wisconsin Natural Heritage Inventory database. The map is provided as a general reference of where this species has been found to date and is not meant as a range map.

Documented locations of Fraxinus quadrangulata in the Natural Heritage Inventory Database as of July 2015.

Summary Information
State StatusTHR
Federal Status in Wisconsinnone
State RankS1
Global RankG4
Tracked by NHIY

Habitats and landscapes

The Natural Heritage Inventory has developed scores indicating the degree to which each of Wisconsin's rare plant species is associated with a particular natural community or ecological landscape. This information is similar to that found in the Wildlife Action Plan for animals. As this is a work in progress, we welcome your suggestions and feedback.

General habitat information

  • Habitat description: Found in rich upland hardwoods, often with dolomite near the surface.
  • Soils: Moist, calcareous soils.

Natural communities

This table lists the natural communities that are associated with Blue Ash. Scores for natural community associations are: "significant" association (score=3), "moderate association" (score=2) or the species can be present but is only weakly associated with the community (score=1).

Natural communities score
Southern Mesic Forest 3

Ecological landscapes

This table lists the ecological landscape association scores for Blue Ash. The scores (3=High, 2=Moderate, 1=Low, 0=None) also correspond to the map.

Map of the Ecological Landscapes of Wisconsin.

Species guidance

The Endangered Resources Program has developed avoidance measures and management guidelines for plants on the Natural Heritage Working List. These are a work in progress, and we welcome your suggestions and feedback. Sources used in developing this information can be found here.

Avoidance measures

These are specific actions designed to avoid "take" (mortality) of this species.

  • Avoid broadcast spraying of herbicides; use care with spot spraying.
  • Avoid locating landings, staging areas, or access routes on or near known populations.
  • Avoid known individual plant locations and conduct operations elsewhere when they are least likely to cause damage. Ideally, this would involve frozen, snow-covered ground. However, in areas of the state where frozen conditions are unreliable, very dry soils late in the growing season might be the best available alternative. Consult with a biologist, if needed.

Management guidance

Management guidelines are additional considerations that may help maintain or enhance habitat for this species

  • Survey for and control invasive plants prior to conducting timber operations, as these can be spread by vehicles and often respond vigorously to increased light; see forestry BMPs for invasive species.
  • Although maintaining high overall forest canopy is important, silvicultural techniques which open small gaps in the canopy may be beneficial to this species.


Blue Ash Photo.

Photo © Marcie O'Connor.

Blue Ash Photo.

Photo by Bill McNee, Wisconsin DNR.

Blue Ash Photo.

Blue ash is known from only two sites in WI. It grows in somewhat calacreous, wet-mesic to mesic deciduous forests. Like all of our native ashes, it is threatend by emerald ash borer.

Photo by  staff, Wisconsin DNR.

Blue Ash Photo.

Photo © Steven J. Baskauf.

Support for Wisconsin's rare plant information has been provided by the Division of Forestry, the Endangered Resources Fund and the Wisconsin Rare Plant Preservation Fund. To donate, visit the Natural Resources Foundation of Wisconsin [exit DNR].

Last revised: Wednesday, May 05, 2021
Southwest Savanna Southern Lake Michigan Coastal Western Coulees and Ridges Southeast Glacial Plains Central Sand Hills Central Lake Michigan Coastal Central Sand Plains Northern Lake Michigan Coastal Northern Lake Michigan Coastal Northeast Sands Western Prairie North Central Forest Northern Highlands Northwest Lowlands Northwest Sands Northwest Lowlands Superior Coastal Plains Forest Transition