if it is an ash to which the emerald ash borer is attracted ... skip it... i will leave you to research that ... or one of our friends will chime in ...

ken

European mountain ash, Sorbus aucuparia, is so prolific in the PNW it has developed a reputation as a weed tree and is rapidly becoming more commonly listed as an exotic invasive. Generally short lived, it is an exceedingly messy tree, generating a lot of debris as well as considerable fruit drop. Fruit can be very messy, so plant away from drives, pathways or patios. The fruit is much appreciated by birds however. One of my favored childhood memories is watching the robins in our backyard tree getting a buzz on the fermented berries after a good frost! But the birds are also responsible for spreading this tree willy nilly throughout the environment, too. And as a member of the rose family, it is prone to a number of disease issues, not the least of which is a tendency to fireblight. I am not as familiar with the native American mountain ash, but assume it has similar characteristics.

If I were to consciously plant a mountian ash, I'd only consider Sorbus hupehensis 'Pink Pagoda', a superior Chinese form developed by the University of British Columbia with persistant bright pink berries that fade to white, a blue tinge to the foliage and very nice reddish fall color.

based on the above info ... i truely hope the ash borer goes after it.. lol ...

but i suspect it doesnt .. based on being from the rose family ....

ken

Out here is really the only part of North America where a serious collection of them can be built up, as with the Brian O. Mulligan Sorbus Collection at the Seattle arboretum. Elsewhere use of them is limited by cold, fireblight, borers...'Dwarfcrown' is a narrowish selection on the general market of a native North American species (there is more than one). Maybe that would do for you. Many have been planted on streets here but our dry summers do not suit it and comparatively few are doing well.

Here is a link that might be useful: Red Cascade PP 4157 Mountain Ash

Mountain Ash (Sorbus sp.) is not affected by Emerald Ash Borer and completely unrelated to Fraxinus (which the borer targets).

Mountain Ash is more closely related to Roses & Apples and is somewhat vulnerable to the same diseases and pests making it a short lived tree.

It is not a good candidate for keeping as a shrub, it is naturally a small tree (as you have already noticed in the area).

You can underplant it...shouldn't affect the tree.

Look for varieties of these Sorbus species, they should do fine in Southern Ontario
- aucuparia
- decora
- americana
- alnifolia
- thuringiaca
- aria

Simon

S. alnifolia is recommended for its borer resistance, since all other familiar species susceptible where these are prevalent. A few shrubby kinds are cultivared, perhaps the most important of these is very small-growing S. reducta. You might like to see if this is able to be grown in your region, unless you want something larger-growing anyway.