Posts Tagged ‘Castanea dentata)’


Ash trees are a colourful bunch. In Ontario, you can find White Ash, Black Ash, Red Ash, Green Ash, and Blue Ash. The latter is an endangered species, found in just a few locations in southwestern Ontario. The penultimate, Green Ash (Fraxinus pennsylvanica var. subintegerrima (Vahl) Fern), is actually a variety of Red Ash (Fraxinus pennsylvanica Marsh). You’d think with all that colour, it would be a simple matter to identify the species of any given tree. Such is not the case however. In fact, based on colour, one would have to say every ash is a Green Ash! After closely examining the tree above, situated near the barn, and consulting a tree guide, I concluded it is, in fact, probably a Green Ash.


Ash trees have compound leaves, with 5 to 11 leaflets on a central stalk. Leaflets may be stalkless or have a short stem and may be smooth or hairy, depending on the species. The paddle-shaped seeds hang in clusters. Recently, driving down the road I noticed a lot of silvery trees along the forest line. On looking more closely, it became apparent that the silver trees were ash trees, and their abundant crops of seed clusters were catching the light, giving the trees a silvery appearance.


Trees are impressive plants. So massive, so substantial, so…big. You wouldn’t think an organism as small as a fungus or a wee bug could kill a tree. And yet exactly that is often the case. Take Dutch Elm Disease (DED). It’s a fungal disease that is spread by the elm bark beetle. The disease was first reported in North America in 1928, believed to have arrived with a shipment of logs from the Netherlands. It went on to devastate elm trees across the east, with 80% of the elms in Toronto dying. The Elm Recovery Project is looking for DED-resistant elms to produce a new generation of resistant trees.

And then there is the American Chestnut (Castanea dentata), a large deciduous tree native to eastern North America. A population once estimated at over 3 billion trees was all but wiped out by Chestnut Blight, a fungal disease introduced to North America on imported Asiatic chestnut trees. Scientists are working on a Chinese Chestnut-cross to produce a blight-resistant hybrid with 94% American Chestnut genes.

The ash tree is threatened by the Emerald Ash Borer (Agrilus planipennis), yet another imported species. Since it was first discovered in Windsor, Ontario and Detroit, Michigan in 2002, it has killed millions of ash trees in southwestern Ontario and Michigan. In 2007, the Borer was discovered in Ottawa, not too far from here. Measures to limit the spread of the insect are in place, but it remains to be seen how destructive this latest invasion will prove to be. It would be heart-breaking to lose these lovely trees.


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