Why can’t Bank Street trees survive and thrive?

by Jennifer Humphries

Black locusts, planted in Lansdowne to replace the 70 trees that have died there since reconstruction, are salt tolerant; however, a lack of diversity is a concern. Photo: Jennifer Humphries
Black locusts, planted in Lansdowne to replace the 70 trees that have died there since reconstruction, are salt tolerant; however, a lack of diversity is a concern. Photo: Jennifer Humphries

You’ve noticed the dying trees along Bank Street. Maybe you’ve seen broken branches and noticed the trash in the narrow, iron-fenced “planting spaces” (variously called death boxes, tree coffins and shallow graves).

These days, our street trees aren’t expected to live more than a few years and most of the ones on Bank Street seem to have considerably shorter lifespans.

Cities worldwide have built grand boulevards shaded by majestic trees. What do these cities know that we don’t? Why is it that Ottawa’s street construction and reconstruction projects haven’t succeeded in getting us even partway to a green canopy?

Simply put, we plant urban street trees in ways that severely limit their chances. Underneath our sidewalks and paved roads is a tangle of rock, dirt, pipes and cables. But trees need good soil and ample root space.

James Urban, an expert in urban trees and soils, wrote on the Deeproot website, “The success of a tree is fundamentally linked to the soil in which it grows…. trees must be put into built environments in entirely new ways.”

In 2013, the City of Toronto engaged experts including Urban to help them address their street tree challenges. Toronto wanted to grow large-canopy trees with a complete 40+-year lifespan. The resulting document, “Tree Planting Solutions in Hard Boulevard Surfaces: Best Practices Manual,” provides detailed information on options to meet this goal. The city followed up with a strategic forest management plan designed to take Toronto from its current tree canopy cover, estimated at 26 to 28 per cent, to 40 per cent over the next 40 to 50 years.

Here in our city, Velta Tomsons of Ecology Ottawa says that Ottawa has a Greenspace Master Plan on the books, but it’s limited. She encourages the city to incorporate “greenness” into all of its planning and development. On trees, Tomsons is guardedly hopeful: “Ottawa’s Urban Forest Management Plan (UFMP) is a good step. But now we need a major step forward to implement it. The plan highlights a lot of the problems we have so we know better and now we need to do better. We’re very cost-focussed but not sustainability focussed. For trees, to keep them growing… we need to do more with the ground under our greyscapes… We need to have soil standards and soil cells and there are best practices already available that we can adapt and adopt for Ottawa.”

Soil cells are “rigid modular systems that are used to increase the soil volume under paved surfaces in ultra-urban areas.” Using soil cells in hardscape planting vastly increases the likelihood that trees will establish and live to maturity. Soil cells have been tried in Ottawa, but not frequently. Wendy Hunter, a member of the Greenspace Committee of the Dalhousie Community Association (DCA), says that soil cells were used in 2013–2014 for some tree plantings on Bronson Avenue north of Gladstone. While the association isn’t aware of which trees were planted in this way, in general the survival rate of the trees seems relatively good, given the heavy traffic on Bronson. A current DCA concern is limiting the impact on our trees from intensification development on streets close to new light rail stations. Hunter says, “We are all in favour of improved intensity near these stations but developers now appear to be granted adjustments to allow new buildings and renovations to exceed city height plans and to solidly fill the city lot from the narrow edge of the back property line to the street, greatly reducing the soil, light and space needed for healthy large trees on those properties and adjacent ones.”

Like Tomsons, Hunter is cautiously optimistic: “Our best hope for improving the environment for the survival of our trees is in the implementation of the new bylaws under the Urban Forest Management Plan. Our hope is contingent, however, on the city improving its enforcement of bylaws, which in the past has been weak.”

Ottawa Sports and Entertainment Group (OSEG) is making efforts to re-tree the streets within Lansdowne Park after the failure of 70 trees planted during reconstruction. Carol MacLeod, a member of the Glebe Community Association Environment Committee, keeps in touch with OSEG in this regard. The new plantings, she says, are black locusts, which are salt tolerant. OSEG is also trying some new planting and tending measures. Still MacLeod is concerned that both the city and OSEG continue to plant the same species on our streets, rather than aiming for diversity. She says, “Along the west side of Bank Street, the city planted only a kind of elm which is marginally more resistant to Dutch elm disease, which has reappeared in our community, than the American elm that used to line Clemow Avenue. In Lansdowne, OSEG has not learned this lesson and has planted avenues of black locust.”

The private sector has a big role to play in making Ottawa the green, treed city it ought to be. So has the public sector. And so have we the people who live, work and play here and who welcome other Canadians and international visitors.

So please, City Hall and forestry department; ensure that all of us are part of the UFMP. And let’s get our proverbial act together to make Ottawa truly green.

Jennifer Humphries is co-chair of the Glebe Community Association’s Environment Committee. You can contact her at environment@glebeca.ca.

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