This tree has the paired stems, and compound leaves, of a Manitoba maple (Acer negundo). These trees are often considered a ” problem ” tree, as they grow very fast, often in tightly squeezed spaces, or against fences. Further, Manitoba maples are a very brittle tree: that is, the wood of mature, large trunks and branches easily split, and can pose a danger.
Also, this tree is growing right on a fence line. The tree will, as it grows, eventually push out the fence. You might consider pulling the tree out, sooner, as it will most likely be a problem, later. The City of Toronto Forestry Operations, under their listing of Invasive Species, says: ” Some invasive plants, such as Manitoba or Norway maple, easily out-compete other vegetation, and will dominate a site if they are not controlled.”
If you wish to plant a new deciduous tree, or a shrub, or an evergreen, in that location, you may want return to the TMG website, where you will be able to find many questions and answers regarding selecting a variety that might work well for that location.
Please visit. http://www.torontomastergardeners.ca.