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
Ash trees have opposite compound leaves. Ash can be monoecious or  dioecious depending on the species. Seeds are contained in a single winged samara (a seed in a papery tissue). Ash wood is valued for its strength and hardness. Black, Red and White Ash grow in Ontario, as well as two Carolinian species, Pumpkin Ash and Blue Ash. Unfortunately, the Emerald Ash Borer has killed millions of Ash trees (see the Tree Diseases page). Black Ash has been the most susceptible to the insect, while Blue Ash shows some immunity.

TREE FACT: Ash and Hickory are similar with compound leaves, but Ash leaves are opposite while Hickory leaves are alternate.
TREE FACT:  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.

This Blue Ash is just starting to turn its greenish-yellow autumn colour.
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.

Mature bark of Blue Ash

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