Mystery plant

(Question)

I’m in Toronto and live on the 15th floor of a building facing south. I noticed this plant growing in one of my containers after my first year living here. It’s survived for 2 winters in its pot and is now this big. Its a woody plant with elm looking leaves. Is this a tree or a shrub?

 

(Answer)

Your photograph appears to show the Siberian elm, Ulmus pumila, which is a prolific self-seeder in Toronto, and this is most likely how it ended up in your balcony container garden.  Although it is sometimes sold as a quick-growing shrub, it is in fact a tree.  Here is an interesting blog post (by a Toronto Master Gardener) that clearly shows how large these plants can get when they have the chance.  Of course, in your balcony container, your plant’s growth will be curtailed.  It is hardy enough to overwinter in a container in Toronto.   In many locales in North America this non-native is considered an invasive species because of its ability to self-seed so successfully.   As large trees in Toronto, Siberian elms present a problem because they are tall and lanky, which makes them vulnerable to damage in heavy snow and ice storms.