planting a tree between 2 toronto driveways

(Question)

i live in midtown toronto with a 2 and half feet wide strip of grass (on my property) that is between mine and my neighbours east facing driveways. The grass is currently covered with black plastic.

I would like to plant a tree in this space, a few feet back from the sidewalk, for some shade to the driveway and to create a nice view from my upstairs kitchen window. Can you advise what tree is suitable given the narrow space? i.e.: a tree whose mature trunk is not too wide for the space, and whose root system will not damage the driveways on either side.

I would have liked to plant a single trunk birch but i believe its roots would potentially damage the driveways.

My other choice is eastern redbud trained to have a single trunk and pruned to give enough clearance for the driveways underneath. Any feedback or further suggestions would be welcome.

(Answer)

Well it is wonderful that you want to plant a tree. Whatever the species, it would be beautiful to look at from your upstairs kitchen window and would provide shade, if you could provide the right nurturing environment for it. Unfortunately the 2 ½ foot strip of grass between your driveway and your neighbour’s driveway is not an ideal space for planting any kind of tree for several reasons.

The average root system of trees grows to be about one and half times larger than the tree canopy. Those roots need to spread out to anchor the tree as it grows and provide the moisture that the tree needs to live and thrive. Hard surfaces like paved driveways prevent moisture from entering the ground, and therefore deprive that tree from getting the sufficient moisture it needs to live. Those roots could also cause a lot of trouble for both driveways situated on either side. For example you suggested an Easter Redbud. That tree canopy can grow to be about 25 feet meaning the roots might extend 30-40 feet. While a smaller columnar tree might be contained to the 2 ½ feet available on the surface the roots would still expand beyond that area and would suffer the consequences of lack of moisture, likely killing the tree. A arborist from the University of Georgia provided these guidelines “Don’t plant large growing trees within 20 feet of sidewalks or driveways, and small trees (under 20’ in height) no closer than 10 feet. http://www.gfc.state.ga.us/community-forests/ask-the-arborist/TreeRoots-Driveways-Sidewalks.pdf

Perhaps you would consider planting shrubs or grasses in the dividing strip between the driveways instead. Many ornamental grasses grow quite tall, are extremely hardy, drought tolerant and very long lived. Alternatively there a variety of shrubs that are know as good foundation plants as they can grow close to houses where their roots will not cause problems for the structure. They include Broadleafed Evergreens like Boxwood (Buxus spp.), and Conifers like Yews (Taxus spp.) and Junipers (Juniperus spp.). Given their smaller size and smaller root structure these options might be perfect for the space provided.

I hope that you find a solution that works for you and the selected plant material.