April 24, 2026

Leith Wheeler’s Focus on Philanthropy: Trees for Life with Mark Cullen

On a cool November day in 2014, a tree was planted at the coroner’s office in Toronto. It was not a ceremonial sapling destined for a photo and a forgotten plaque. It was the first tree in what would become a living memorial stretching 170 kilometres along Highway 401. For Mark Cullen, it was the quiet start of something that would come to define the next dozen years of his life.

“We started with nothing,” Cullen said. “We had an idea. That was it.”

The idea was deceptively simple. Canadians killed in the Afghanistan conflict were being repatriated through CFB Trenton and driven along the Highway of Heroes to Toronto. Cullen and a small group of board members asked themselves whether that stretch of road could become more than a route of mourning. What if it could become a place of remembrance rooted in something living?

“At first, the idea was, ‘let’s plant a tree for every Canadian lost in war,’” Cullen said. But it did not stop there. As the numbers came into focus, while about 117,000 Canadians have been killed in combat, Cullen said, he was struck by a second statistic that few Canadians knew: more than two million Canadians had volunteered for military service during times of war, over the country’s history. Volunteers, not conscripts. People who put up their hands and said yes.

“And so we planted 2.1 million trees,” he said.

To fund it, over the next decade Trees for Life and its predecessor campaign raised $10 million, roughly half from private citizens and corporate donors, the other half from federal and provincial governments. The final tree was planted at Fort York with former governor general the right honorable David Johnston in attendance. 

It would have been a natural moment to step away but instead, Cullen and his colleagues looked at what they had learned and made a different decision.

“We weren’t quite ready to go play more golf,” he said, with a laugh. “We wanted to do more.”

Helping Cities Breathe

Cullen and his partners saw that clearly the next big opportunity was not along highways or rural roads. It was in the cities. Every city they visited told the same story of shrinking urban tree canopies, as development, climate stress, and infrastructure had left little room for mature trees to survive.

“There isn’t an urban centre in Canada where the tree canopy isn’t in decline,” Cullen said. “And the benefits of trees accrue to us most where we live with them.”

He likes to put it simply: the tree that benefits you most is the one in your backyard. Under that tree, the air is cooler, richer, and quieter. A mature maple can lower temperatures on a hot day by as much as ten degrees Celsius and can release hundreds of litres of water into the air. It anchors soil during heavy rain and offers shade on a blazing afternoon.

“Every storybook you ever read as a kid, people gathered under a tree,” Cullen said. “There’s a reason for that.”

Trees for Life was born out of that understanding. The organization shifted its focus entirely to urban spaces, planting not seedlings, but what Cullen calls “teenage trees.” Standing four to seven feet tall, they are expensive compared to reforestation saplings, but far more resilient. With proper care, survival rates exceed 85%, a number that raises eyebrows in forestry circles.

“We don’t just plant trees,” Cullen said. “We grow trees.”

While his passion is palpable on the call, Cullen’s credentials to tackle this problem are substantial. 

Long before Trees for Life existed, Cullen spent decades helping Canadians notice what grows quietly around them. In addition to spending 17 years as Home Hardware’s national spokesperson for Lawn and Garden, he hosted gardening programs on CBC, CTV and HGTV, wrote thousands of newspaper columns, and for years was a familiar Friday presence on Canada AM, translating soil, shade and seasons into language Canadians could understand. It’s clear that gardening, for Cullen, has never been ornamental. It is practical, observational and deeply human.

What surprised Cullen most was not the science or the logistics, though both were complex. It was people: volunteers, donors, and entire communities that showed up again and again, often asking for nothing in return.

“We have more than 6,000 volunteer tree planters and over 4,500 donors,” he said. “Some people give $50. Some give a lot more. What’s surprising is how many people simply want to be part of it.”

Part of that willingness comes from the way Trees for Life connects nature with the human story. During the Highway of Heroes Tree Campaign, Cullen noticed a pattern. When trees were framed purely as environmental assets, support was steady but quiet. When trees were connected to remembrance, support surged.

That insight led to the Hero Trees program. For a modest donation, a tree can be planted in honour of someone who mattered to you: a family member, a healthcare worker who made a difference, even a beloved pet. The tree comes with a certificate and a name, but more importantly, with a sense of permanence.

“It acknowledges that Canadians are people, too,” Cullen said. “What touches us is the connection between nature and the human condition.”

 

Today, Trees for Life plants trees in cities across the country, including projects in Alberta and British Columbia. To coincide with Earth Day this year, the organization partnered with the Arbor Day Foundation to plant trees in Richmond, BC. More projects are planned throughout the Lower Mainland and other dense communities where trees are needed most.

All of it raises a quiet but important question: how do people support work like this in a way that fits into their broader financial lives? One answer is through donor advised funds. 

Donor Advised Funds

For many, charitable giving happens sporadically so over time, that can disconnect you from long-term goals. One option families are increasingly considering is a donor-advised fund (DAF). As we outlined in this Explainer article, a DAF allows individuals to easily donate funds to an account, which provides an immediate tax receipt but then the flexibility to direct the donations of that account over time. It brings structure and intention to philanthropy without urgency or pressure.

We offer donor-advised funds at Leith Wheeler as part of a broader conversation about stewardship beyond wealth preservation. It’s about investing in causes that reflect your values.

Cullen understands that instinctively. Late in the conversation, when asked about legacy, he hesitated.

“I don’t really think about my legacy,” he said. “What I think about is what engages Canadians.”

Still, the answer came back to the future. Cullen is a grandfather now, eight times over. He thinks about the world his grandchildren will inherit and what they will ask of his generation.

“I don’t want them to say Grandpa grew up in a generation that abused the Earth,” he said. “I want this to be part of the answer.”

The trees planted today will not reach their full environmental potential for 30 years. No one involved today will benefit personally from their maturity. That, Cullen believes, is the point.

“Nobody can look at us and say we’re doing this for selfish reasons,” he said.

A tree planted in a city is a quiet act. It does not call attention to itself. It grows. It shades. It holds the ground together. Over time, it becomes part of the life around it. Trees for Life is built on that same idea. That the most meaningful change often starts small, takes patience, and lasts far longer than we do.

For those considering how to give, or where to direct their generosity, that is worth thinking about. 

 

For more information

• Click here to learn more about Trees for Life
• Click here to learn more about Donor Advised Funds
• Click here to connect with a Leith Wheeler professional about your investing and philanthropic goals

Contributors: