Why are there so many cones on spruce trees this year? Experts offer answers

If you've recently walked down a street and stopped in your tracks after spotting far more cones than expected on a spruce tree, you're not the only one. 

According to Ed Johnson, Professor of Biological Sciences at the University of Calgary, this year is turning out to be unusual for spruce trees across Calgary and he reckons he hasn't seen such a large number of cones in 40 years.

"Lots of people have looked at them from a distance and said, 'oh my goodness, these trees look like they're dying,'" he said. "And in fact, of course, it's not that, it's just a lot of cones." 

Johnson added that spruce trees tend to follow a random pattern that's hard to predict. Producing cones is a "survival strategy" that plants use to protect themselves from seed predators.

"Most years there's very little seeds being produced and the seed predators can't harvest a lot of it," Johnson said. "But randomly they produce large numbers of seeds … which satiates the predators and so consequently more seeds survive." 

The most common predators in this scenario are birds, insects and squirrels, according to Johnson.

Gerard Fournier, arborist and founder of For Trees in Alberta said that the cones that we're seeing right now are actually from 2022. 

"Trees make their cones in the summertime," he said. "So all the cones that you can see on the tree right now were made in the summer of 2022."

LISTEN | Ed Johnson talks about the massive number of cones on spruce trees:

Fournier added that the hot and dry weather in 2021 "stressed the trees out" and led to a massive number of cones last year. 

"You could sort of imagine it as if the trees think that their lives are in danger and they got to put a lot of energy into reproduction," he said.

While Fournier thinks that this year's outlook isn't as dramatic as last year, he acknowledged that the average homeowner should examine their spruce tree to check whether it's "bent over" and is being affected by an unusually large number of cones. 

 "You should probably call an arborist if you see that happening on your tree," he said. 

According to Fournier, trees may get damaged or "even break under the weight of so many cones" and it's a good idea to stay alert and look for signs of damage.

'It slows down the growth rate of the trees'

What does producing so many cones do to trees in the long run? Fournier has the answer.

"It slows down the growth rate of the trees, especially in subsequent years," he said. "And so what also can happen is in subsequent years there's not enough energy for the trees to produce any cones."

Fournier said that in such a scenario, it's not uncommon to see trees taking a break to get some rest. The arborist says there will likely be fewer cones for a bit before things pick up again in 2025.

Johnson finds the entire process rather fascinating and is impressed by nature's survival instinct.

"The thing that sort of staggers … me is the fact that really an individual spruce tree, or any tree for that matter, only has to reproduce itself with a tree that will grow up and produce more cones," he said.

"But to do that it has to literally, over its lifespan, produce millions of seeds in hopes that one of those seeds will eventually make it."