Commercial buildings with green roofs and gardens on their grounds can contribute to climate resiliency and biodiversity while reducing maintenance costs, Jessica Milligan, president of Montreal-based Strathmore Commercial Landscape Management, said.

Most property managers prioritize interior operations when it comes to making a sustainable building, but “a lot of commercial real estate can be optimized to build more resilient, biodiverse landscapes” which should not be ignored, she told Sustainable Biz Canada in an interview.

Consider a pollinator garden with native flowers which attracts bees, butterflies, beetles, birds, flies and wasps: it uplifts biodiversity and the natural beauty promotes tenant engagement and well-being. Roofs with vegetation can cool cities during sweltering summers and absorb heavy rainfall.

“Long-term, if you incorporate some of these ideas, it’s going to be lower maintenance costs. The cost of cutting grass every single week, watering it, fertilizing it in perpetuity is higher,” Milligan said.

Her experience is informed by the work Strathmore has done for commercial real estate firms such as Colliers and asset managers and property owners that work with Cadillac Fairview, Canderel and CBRE. Operating Canada-wide, Strathmore maintains 400 to 500 commercial, industrial and institutional properties, and has begun expanding to the U.S.

Green plants, green savings

Pollinator gardens featuring native perennials and plants carry a bevy of advantages. They can cut maintenance costs compared to manicured lawns by 70 per cent after three years, Milligan said, by reducing the need for frequent intervention.

Another advantage of green spaces is promoting tenant engagement. As workers return to office amid some reluctance and a desire for well-being amenities, the natural beauty of a roof or garden decorated with a colourful bouquet of flowers can promote engagement. For Colliers, Strathmore has put up QR codes on a garden that provide details about the plants when scanned.

“The properties look better, the air quality’s improved, comfort is improved,” Milligan said. Plus, more plants and soil in cities helps store away carbon.

Some studies have suggested the exposure to plants on a green roof improves well-being and improves productivity.

With pollinator populations on a sharp decline, planting gardens that support their numbers with native flowers and vegetation as opposed to lawns is an ecological win.

Food insecurity can be tackled with urban agriculture on green roofs and gardens. At the Centropolis mall in Laval, Que., Strathmore has cultivated crops such as cabbages and peppers which are donated to local food banks.

Promoting climate resiliency

Gardens and green roofs absorb more rainwater than lawns, Milligan said, a form of climate adaptation that is receiving greater attention as some cities experience extreme rainfall from a warming climate.

A study by University of Toronto civil engineers found green roofs have the capacity to capture an average of 70 per cent of rainfall over a given time, which puts less pressure on underground stormwater systems.

Increasing the amount of plants on commercial properties helps cool down cities, a valuable attribute as temperatures are rising globally. A 2023 study in the journal Renewable and Sustainable Energy Reviews found green roofs can reduce the cooling load of a building by up to 70 per cent and decrease the surface air temperature up to 15 C compared to a conventional roof.

Green roofs have been found to produce annual energy savings from 10 to 60 per cent for space cooling.

The biggest obstacle to the case for a green roof or pollinator garden is “almost always budget,” Milligan said. The high upfront initial investment is often challenging to justify. But Strathmore has built small proof-of-concept projects for skeptics, and after three years, most clients are usually on board and have no desire to go back, she added.

Milligan also pointed to how sustainable landscaping grants point toward green building certifications such as LEED, GRESB and WELL, which increase the value of a property and reduces its risks.

Strathmore's green landscaping crews

Strathmore is taking measures to improve the sustainability of its landscaping. The company launched three zero-emissions crews earlier this month in Montreal and Ottawa that use zero-emission trucks and battery-powered hand tools (blowers, hedge trimmers, chainsaws) and compost vegetation.

“We were ready for that crew to cost us more, to be less efficient, to really be a novelty. And that wasn’t the case,” Milligan said. Smaller trucks meant crews could park closer to a job site and get to work faster, and two workers were now needed, not three. The battery technology kept up with gas-powered equipment.

Efficiency went up 30 per cent and allowed Strathmore to be better aligned with the sustainability goals of its clients, she said.

Technology that measures the increase in pollinators visiting gardens is an innovation that excites Milligan. As many of the proof points of landscaping are not backed by much hard data, she hopes installing sensors that track the change in pollinator numbers will deliver the evidence.