Blue Ash
Fraxinus quadrangulata

Location in Ontario

Blue Ash is a rare Carolinian Tree that grows in Lambton County, Point Pelee, Pelee Island, Middlesex County and Elgin County. Blue Ash grows on floodplains and rocky outcrops.

COSEWIC (Committee on the Status of Endangered Wildlife in Canada) Status:
Blue Ash is identified as a Threatened species. This is due to its limited range in Canada, loss of habitat and the effects of Emerald Ash Borer.


Blue Ash in fall colour of greenish-yellow, University of Guelph Arboretum
Genus Fraxinus
Leaves: Compound, opposite
Flowers: Monoecious or dioecious
Fruit: Samaras (a seed in a papery tissue)
Ontario Species: Black Ash, Red Ash, White Ash, Pumpkin Ash (Carolinian), Blue Ash (Carolinian)
Other facts:
*Ash trees are at risk to the Emerald Ash Borer (see the Tree Diseases page).
* Ash and Hickory are similar with compound leaves, but Ash leaves are opposite and Hickory leaves are alternate.
*A spring rhyme, referring to which leaves appear first; Oak before Ash you get a splash, Ash before Oak you get a soak.

In the Landscape
Blue Ash is a small, slow growing tree, reaching 20 metres and living to 150 years. It is a lovely tree with distinctive winged branches, and pretty purple flowers in the spring. Blue Ash is at risk to the Emerald Ash Borer, but has shown some resistance to it.

TREE FACT: When the outer bark of Blue Ash is rubbed off, there is a bluish inner bark. This was used to make blue dye by Native people and early settlers.

Watch the Carolinian Tree Profile for Blue Ash on YouTube:

Carolinian Tree Profile: Blue Ash
Leaves: Blue Ash leaves have 5-11 leaflets which are coarsely toothed, long and pointed. Leaves turn greenish-yellow to light yellow in the fall.
Bark: The bark is gray and scaly, without the diamond pattern of other Ashes. Branches are ridged on four sides, leading to the name "quadrangulata".
Flowers: Unlike the other Ashes, Blue Ash is monoecious with perfect flowers. The flowers are small and purple coloured, and appear in early spring before the leaves. They are wind pollinated.
Fruit: Seeds, which are samaras, form in summer, and fall off in early autumn; however some seeds persist into winter. Seed production is variable, but usually occurs every 3 to 4 years, once the tree has reached 25 yef age.
Blue Ash wood is hard and heavy, but not as heavy as White Ash. It is darker in colour and sold as White Ash.
Specific Gravity:
Janka Hardness: 1290 lb
Wood Comparison Chart
Blue Ash is diploid. It does not form hybrids.

Blue Ash is not included in the United States Forest Service Silvics Manual.