and Deciduous Forest Trees

of Southern Ontario

Blue Ash
Fraxinus Quadrangulata

Location in Ontario:
Blue Ash is a Carolinian Tree that grows in Lambton County, Point Pelee, Pelee Island, Middlesex County and Elgin County.

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 with 5-11 leaflets. 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.
Emerald Ash Borer is an invasive beetle accidently brought to North America from Asia in shipping boxes in 2002. It has quickly spread killing millions of Ash trees. Blue Ash has shown some immunity. There is a pesticide that can be used to control Emerald Ash Borer, but it is very expensive, and must be administered every two years. Unfortunately, many non-infected Ash trees have been cut down as a preventative measure. This eliminates trees that may have had a natural immunity. For more information and encouraging news about saving Ash trees:
Save the Ash Tree Coalition

The tell-tale tracks of the Emerald Ash Borer

Habitat: Rare in Canada, Blue Ash grows on floodplains and rocky outcrops.

Landscape Use:
Unfortunately, Ash are at risk to Emerald Ash Borer, however, Blue Ash has shown some resistance. It is a lovely tree with distinctive winged branches, and pretty purple flowers in the spring. Its growth is slow and steady.

Leaves: Blue Ash leaves have 5-11 leaflets which are coarsely toothed, long and pointed.

FALL COLOUR WATCH: greenish-yellow to light yellow

Flowers: Unlike the other Ashes, Blue Ash is monoecious with perfect flowers. The flowers are small and purple coloured, and appear in early spring.

The purple flowers of Blue Ash

Fruit: Seeds (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 years of age.

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".

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.

Mature bark of Blue Ash

Size: Blue Ash is a small, slow growing tree, reaching 20 metres and living to 150 years.

Wood: Ash wood is hard and heavy. Blue Ash is not typically used in Canada due to its rareness.
Specific Gravity:
Janka Hardness: 1290 lb
Wood Comparison Chart

Genetics: Blue Ash is diploid. It does not form hybrids.

This Blue Ash is just starting to turn its greenish-yellow autumn colour. Lawn specimen, Norfolk County