Tag: plants

Hot sum­mer reflec­ted in fall foliage

Autumn enthu­si­asts may be dis­ap­poin­ted as leaves change col­our earlier due to extreme heat

The extreme heat and fewer days of rain this summer are contributing to the early browning of some trees, especially those more susceptible to the effects of dry weather.

This article was written by Asma Sahebzada and was published in the Toronto Star on September 21, 2025.

Autumn enthu­si­asts may be dis­ap­poin­ted as leaves change col­our earlier due to extreme heatSaveListenSharePrintMore

One of the more not­able mark­ers of fall arriv­ing is the change in the col­our of leaves, and this year, you might’ve noticed the red, yel­low and brown are appear­ing earlier than expec­ted.

Although when this autum­nal col­our­a­tion exactly hap­pens depends on the type of tree, some are chan­ging sooner than nor­mal, which could bring duller and patch­ier fall foliage this sea­son, experts said.

And, if you’re an autumn enthu­si­ast, it could also mean a dis­ap­point­ing back­drop for your pho­tos.

Monday marks the first offi­cial day of fall in Toronto but the city has yet to feel cooler tem­per­at­ures, as warm weather from an unbear­ably hot and humid sum­mer lingers.

The extreme heat and fewer days of rain this sum­mer are con­trib­ut­ing to the early brown­ing of some trees, espe­cially those more sus­cept­ible to the effects of dry weather, explained McMas­ter Uni­versity bio­logy pro­fessor Susan Dud­ley. Instead, she said some tree leaves might die off before turn­ing red.

As fall arrives, here’s what you should expect to see when going on a stroll throughout the city.

Cer­tain spe­cies of trees in the city are facing pre­ma­ture leaf death, said Dud­ley, who has also noticed the early col­our change in trees on the McMas­ter cam­pus in Hamilton.

This is because Toronto and much of south­ern Ontario saw record­break­ing heat this sum­mer and a long rain­less period in August, accord­ing to Sean Thomas, a Uni­versity of Toronto pro­fessor whose expert­ise is in tree bio­logy.

“What you usu­ally see under those con­di­tions is pre­ma­ture sen­es­cence of leaves,” Thomas said, adding that signs of stress are the brown­ing of the leaves and branches dying.

The tran­spir­a­tion pro­cess from tree leaves is related to both heat and humid­ity so if a lot of water is being lost from the leaves, even if there’s enough water in the soil, drought responses in the trees are induced, he said.

When cooler tem­per­at­ures and shorter days arrive, a leaf’s green chloro­phyll is broken down, reveal­ing the under­ly­ing yel­low and orange col­ours.

When a tree’s leaves change to red, they pro­duce antho­cy­anin pig­ments that have the func­tion to pro­tect the leaf dur­ing the sen­es­cence pro­cess, so that the nitro­gen can be recovered in the tree from the break­down of chloro­phyll. Dud­ley calls this pro­tec­tion a “type of sun­screen” for the meta­bol­ism within the leaf after the chloro­phyll is gone.

But this pro­cess can be triggered early under drought con­di­tions, Thomas added.

Many decidu­ous trees change col­our in the fall includ­ing the sugar maple and oak trees that pro­duce the vibrant red, orange and yel­low leaves seen in Toronto.

Although heat and drought con­di­tions can lead to brown leaves and duller fall foliage, some trees can be at more of a dis­ad­vant­age than oth­ers based on loc­a­tion and access to water.

Trees planted on school cam­puses, streets or parks are gen­er­ally more stressed than those in forests where they’re clustered and receive more shade. Trees in city parks and those planted fur­ther apart don’t exper­i­ence as much of the shade that might help pro­tect them from the sun dur­ing intense heat waves. They may also suf­fer more soil com­pac­tion from people walk­ing near them, which hinders water infilt­ra­tion.

Dud­ley said maple trees may be more at harm than trees like oaks, as maple trees usu­ally thrive in cooler, moist con­di­tions while oak trees are more adapt­able to drought con­di­tions.

Due to the early autum­nal col­our­a­tion, res­id­ents will notice patchi­ness in a group of trees where there will be some chan­ging col­our early while oth­ers won’t be. This all depends on the trees’ access to water dur­ing grow­ing sea­son.

Some trees that are “highly stressed” over the heat and lack of water could even see its leaves turn from green to brown, indic­at­ing “dead leaves.” As res­ult, the fall col­ours of the trees will be less vibrant and have a duller appear­ance.

“Early change is a sign of stress very often, even if it’s a nice red col­our. When they change in Septem­ber, it’s like an indic­a­tion that the tree might be stressed,” Dud­ley said.

One year of drought con­di­tions is not a prob­lem, explained Thomas, but if Toronto’s trees exper­i­ence early leaf col­our change for mul­tiple fall sea­sons, then this can really add up to the stress the trees exper­i­ence.

“I’ve cer­tainly seen some dead trees around, so they might have been on a site where they’ve had other prob­lems or they have dis­ease impacts. So there’s cer­tainly this kind of drought con­di­tions can be a real prob­lem for indi­vidual trees. There’s not wide­spread die­back. But, we need to hope that we won’t see another drought here next year,” he said.

We don’t need to cut down majestic old trees for the holidays

This opinion was written by Jennifer Cole and was published in the Globe & Mail on December 2, 2024.

A nun takes a photo of the 100-foot tree in St. Peter’s Square last month. A petition with 50,000 signatures had called on Pope Francis to stop the ‘execution’ of the tree from Italy’s Trentino province.

It’s the most wonderful time of the year – except if you are an 80-year-old evergreen tree. Every year cities and towns worldwide go to great lengths to choose a majestic tree to become the centrepiece of their festivities. This year, however, the tradition is being questioned.

In Italy, 50,000 people signed a petition calling on Pope Francis to stop the “execution” of a live 100-foot evergreen tree from Trentino province destined for the Vatican. They said killing the tree, which is now at St. Peter’s Square, was unnecessary and would deprive the local environment of its ecological benefits. However, local officials have said that if the tree hadn’t gone to the Vatican, it would have been cut to comply with EU forestry management practices.

Old stately trees, as the Italian protesters rightly point out, are vital parts of the ecosystem. They are self-sustaining habitats for birds and small animals. The cones and needles of evergreen trees are a source of winter sustenance for wildlife. Living trees absorb carbon – the amount varies depending on the type of tree and its size. The Tree Council of Ireland suggests that a 10-year-old evergreen absorbs 14 kilograms of carbon dioxide a year. Yet, despite these arguments, the practice of felling mature trees for the sake of holiday magic continues.

On Nov. 7, a 74-foot Norway spruce was cut down, placed on a flatbed truck and made the journey from West Stockbridge, Mass., to New York’s Rockefeller Center. On Nov. 12, a similar tree arrived in Toronto’s Nathan Phillips Square – a majestic white spruce from Bancroft, Ont. It was decorated with more than 500 ornaments, with a big reveal happening this past weekend.

Some cities have been rethinking the tradition. In France, the city of Bordeaux discontinued the practice in 2020, much to the chagrin of citizens. A poll showed that 79 per cent of people in France disapproved, yet the mayor’s deputy defended the decision, citing costs for a tree that would end up in the trash. Cost also played a role in Edmonton, when in 2022 the Edmonton Downtown Business Association said paying for a large real tree didn’t make sense any more.

In Vancouver, the giant tree in front of the Vancouver Art Gallery is a 76-foot artificial cone. No one complains. A study released by the American Christmas Tree Association suggests that artificial trees have a more favourable effect on the environment if used for at least five years.

In fairness, there is some environmental benefit from the sacrificial trees. Toronto’s trees have traditionally been mulched and blended into the soil for future trees to grow from. The tree at Rockefeller Center is handed over to Habitat for Humanity and its wood is used to build homes for families. And yes, new trees will be planted. In Canada, the federal government has recognized the critical role of trees and in 2021, it launched an ambitious initiative to plant two billion trees by 2031, although the plan is behind target. Sadly, though, it will take many decades for those seedlings to come close to the majesty of the ones cut down for this year’s holiday festivities.

When all is said and done, the loss of one tree is enormously sad, but it’s what that loss represents that makes it devastating. The Earth is facing a dual crisis of rapid climate change and unprecedented biodiversity loss. The Copernicus Climate Change Service reports that in 2024, the planet is virtually certain to exceed the 1.5 C limit above preindustrial warming agreed to in the Paris Agreement. A recent UN report on biodiversity estimates as many as one million plant and animal species are threatened with extinction. This includes trees.

The controversy over axing these guardians of nature, as Italian protesters prove, stirs strong emotions. Cutting down one tree is not the end of the world. But it does raise questions about the precedent set when a beautiful, old tree is sacrificed – stripped of its environmental service – all for a fleeting moment of holiday magic. Sure, it looks nice, but it’s hard to argue that it’s necessary. More likely, it’s just another example of the avarice that has got humanity into a tangled mess in the first place, leaving the stewardship of Planet Earth as an afterthought.