Description and habitat

Black Ash (Fraxinus nigra) is one of Long Point’s most ecologically important tree species. In ideal conditions, Black Ash can grow a large tree to 25 m or more. It is one of five species of ash in the Long Point Basin – these include Green Ash (Fraxinus pennsylvanica), Blue Ash (Fraxinus quadrangulata), White Ash (Fraxinus americana), and Pumpkin Ash (Fraxinus profunda). As a genus, ash trees are distributed widely across the Northern Hemisphere. All ash trees in Ontario have oppositely arranged, pinnately compound leaves.

Black Ash is distinguished from the other ash species by habitat preferences, leaf and bark morphology. The leaves are 15-45 cm in total length, with 7-11 leaflets, with serrated leaf margins. The leaflets are sessile – directly attached to the stalk, unlike other Ontario ash species. Leaves are vibrant, deep green. In the autumn, the foliage transforms into a deep yellow. Flowers appear on female trees in May, which transform into winged seeds 3-5 cm long. The fruit is comprised of a winged seed called a samara, measuring 2-5 cm long. It encases the seed completely, unlike White or Green Ash. The bark is comprised of grey to greyish-brown, scaly ridges divided by fissures, giving a slightly flaky appearance.

Across Ontario, Black Ash is found throughout most of the Great Lakes Region. The range of this species extends northwards into the Hudson’s Bay Lowlands, and south into the Ohio Valley. It is common in many areas, especially in lowland regions. Black Ash is an important component of swamps throughout the Great Lakes Region. In the southern Great Lakes, such as the Long Point Basin, Black Ash is usually found in mixed species swamps with White Elm (Ulmus americana), Silver Maple (Acer saccharinum), Red Maple (Acer rubrum), Cottonwood (Populus deltoides), Green Ash (Fraxinus pennsylvanica), and Black Tupelo (Nyssa sylvatica). Black Ash is also found in wet lowlands with Yellow Birch (Betula lutea), Red Maple, and Eastern Hemlock (Tsuga canadensis). In the northern Great Lakes, it often forms pure strands. It is occasionally found in upland forest types (especially those dominated by Sugar Maple, Acer saccharum and Beech, Fagus grandifolia) along creeks, streams, and moist ravines.

Wildlife importance

The winged seeds of Black Ash are consumed by a wide variety of wildlife, including small mammals, songbirds, and waterfowl. The twigs are also a valuable food source for white-tailed deer (Odocoileus virginianus). Black Ash is also utilized by dozens of insect species. These include many butterflies and moths, including the Ash Leaf Cone Roller Moth (Caloptilia fraxinella), Waved Sphinx Moth (Ceratomia undulosa), and the Lilac Borer Moth (Podosesia syringae). Black Ash is an indicator species of a healthy ecosystem in forested wetlands.

Emerald Ash Borer 

Since the early 2000s, Ontario’s ash species are threatened by an invasive beetle from northeast Asia, Emerald Ash Borer (Agrilus planipennis, subsequently EAB). Originally introduced to Detroit and Windsor on shipping cargo, it has since spread across the Great Lakes Region. In the Lake Erie Region, EAB has killed over 85% of mature Ash trees. White Ash has slightly more resistance than Green Ash or Black Ash, and in some of the woodlots, there are healthy ash trees that have survived EAB. Several insect parasitoids have been introduced in an attempt to control EAB populations. This includes four wasps – Tetrastichus planipennisi, Spathius agrili, Spathius galinae, Oobius agrili. Wasp larvae consume the eggs or larave of EAB, resulting in both EAB mortality and large population increases of the biocontrol waps. In combination with natural predators (including Woodpeckers, Picidae, which can consume >50% of all EAB larvae), native parasitoids, and innate host tree resistance EAB, the future goal is to reduce the EAB population so that native ash trees can naturally regenerate into the forest canopy without experiencing EAB-induced mortality.

Fun facts

• In the Great Lakes Region, Black Ash has been utilized by indigenous peoples for basketry (basket making) for countless generations!
• Black Ash is named for the dark colour of it’s inner bark
• It is the most suspectable of Ontario’s ash species to EAB, very closely related to the beetle’s native host tree – Manchurian Ash (Fraxinus mandshurica) of northeast Asia. Though usually considered separate species, some botanists even consider Black Ash and Manchurian Ash to be a single species – making it the only native tree species in Ontario indigenous to both Asia and North America.
• Drainage ditches and tile systems have a negative impact on Black Ash by reducing moisture levels in swamps
• While Black Ash populations have suffered severe declines as a result of EAB, Black Ash is still found in the understories of swamps, a potential opportunity for future restoration if biocontrol efforts are successful.

 

Written by Matthew Palarchio, HBSc in Environmental Sciences, Western University.

Photos by Matthew Palarchio 

 

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