Species of the Month

These species have been featured in our FYI newsletter as "species of the month."

• Brook Lampreys
• Snapping Turtle (Chelydra serpentina)
• Spotted Salamander (Ambystoma maculatum)
• Eastern Hog-nosed Snake (Heterodon platirhinos)
• Blue Ash (Fraxinus quadrangulata)
• Brook Trout (Salvelinus fontinalis fontinalis)
• Wood Frog (Rana sylvatica)
• Smooth Serviceberry (Amelanchier laevis)

Blue Ash (Fraxinus quadrangulata)

Several species of ash tree grow in southern Ontario but one is particularly noteworthy for its affinity for the Thames River. It is the blue ash, Fraxinus quadrangulata.

Blue ash is known from only a handful of areas in Ontario including the floodplains of the Thames, Sydenham and St. Clair Rivers, Point Pelee, and nearby islands of western Lake Erie. Most sites are around Thamesville near Chatham. The most northerly known site of this tree in Ontario is in Fanshawe Conservation Area in northeast London.

In Canada, blue ash is limited to the Carolinian Zone where the climate is warmest and the growing season longest. This tree prefers to grow on rich floodplain forest soils, yet in the Lake Erie islands it grows on shallow soil over dry limestone and well drained sand. This species has a large range south of the border, from Ohio and Wisconsin, south to northern Georgia and Arkansas.

Blue ash are medium-sized trees, growing up to 20 metres (65 ft) tall. The leaves are dark green, emerge opposite from each other on the branch, and feature five to 11 leaflets.

The twigs are quite distinctive, with conspicuous corky ridges that make them four-sided; hence the species name, quadrangulata, meaning four-angled.

Blue ash gets its common name from a sticky substance found in the inner bark that turns blue when exposed to the air. The tree spreads primarily by seed dispersal.

Blue ash leaves (left) have 5 to 11 leaflets, and grow opposite each other on the branch, which has distinctive corky ridges (right).

Because of its limited Canadian range and low numbers, blue ash is designated as a species of “Special Concern” by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) and it is protected under the federal Species at Risk Act. The main limiting factor is probably the lack of suitable habitat, as this species occurs in a highly developed part of Ontario where floodplain forests are limited. The tree also has low reproduction rates in Canada.

Will this ash be susceptible to the emerald ash borer? Probably. Evidence suggests this borer attacks any true ash tree. This raises concern for the blue ash as it cannot afford any additional loss.

Contact: , Terrestrial Ecologist

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