Elm: These are large trees but because of their vase shaped habit often fit into medium to large size city gardens. They make excellent shade trees and are often planted in Calgary as a street tree.
Size and Characteristics:
American Elm (Ulmus americana) mature at 15m (50’) wide by 20m (65’) tall
Brandon Elm (Ulmus americana ‘Brandon’) mature at 10m (32’) wide by 15m (50’) tall
Otherwise they are very similar with a rough grey bark, vase shaped form. The leaves are green with a golden fall color. No ornamentally significant flowers or fruit.
Pests and Diseases: There is one potentially deadly disease of Elms that has resulted in widespread decimation of Elms across most of Europe and North America and it is called Dutch Elm disease. It is a fungal disease spread by a very small beetle that very rapidly spreads throughout the cambium layer of the tree and thus cuts off the flow of water and nutrients between the canopy of the tree and the root system resulting in rapid decline and death of the tree.
In Alberta we have several things going for us in fighting this disease. Firstly is we have no native elms in Alberta as they do from Manitoba east so there are no potential wild infestations. Second is our geography with mountains to the west, cold to the north and prairies to the south and east the beetles etc. can’t easily transfer to our trees (the one way they could come in is in firewood, you’ve seen the highway signs no doubt) Third is municipal and private arborist types have seen this coming a long way off and have set up systems to aggressively deal with the disease if and when it gets here. If you look at any elms in Calgary you will see a metal tag attached with information about who to contact should it appear sick and a reference number. This will provide a quick response to a problem and hopefully prevent its spread. There is also a ban on pruning Elms from April until October which is the window when the beetles are active and thus reduces potential entry points.
Dutch Elm disease has been ‘on the horizon’ for the past 20 years or more and as yet has been held at bay. Hopefully permanently… however, there is that potential. (There is potential for something like that to affect any species but I think I’m done here… you get the point)
The City of Calgary is actively planting Elms as boulevard trees and for a large shade tree for your garden they can not be beat.
© Clayton Ditzler