Fall just wasn’t the same this year.
The leaves on many trees turned dull green or brown instead of the usual red, orange and yellow, and many leaves still haven’t fallen.
Prairie residents can blame it on the weather.
“The sudden change in temperature we had left the trees unprepared,” said Laurie Newsham, a horticulture instructor at Olds College’s School of Environment in Olds, Alta.
“In Olds, we went from 30 degree days to minus 15 very suddenly. The leaves were essentially freeze-dried while still on the trees. Trees can’t run inside to get warm like we can.”
Read Also
Claims filed in Alberta hailstorm aftermath
The numbers are still coming in for the cost of the damage caused by a huge hail storm that hit various areas of Alberta Aug. 20.
Newsham said insects such as aphids and wasps also hung on this fall compared to a more usual season.
“The warm weather earlier this fall was lovely for us, but not for the trees,” he said.
“But these kind of extremes are just part of the Prairies.”
In a normal season, trees spend the long, bright days of summer producing food in their leaves through photosynthesis, which produces the chlorophyll that makes leaves green.
The colourful pigments seen in fall are present in the leaf all summer, but masked by the chlorophyll. They appear in fall when there’s fewer daylight hours and less photosynthesis.
This year, the trees leafed out later in spring because it was so cold. Trees then worked overtime in summer to feed themselves because of the cool, dry conditions.
“The drought was just one more stress the trees had to deal with,” Newsham said.
An early hard frost in late summer then arrested their growth.
But why aren’t the leaves blowing off in the wind?
Newsham said it’s likely because of the shorter season.
The base of a leaf’s stem, called the petiole, is a sensitive area. In the natural process of preparing to lose its leaves, the tree cuts off the flow of nutrients to the leaves and then builds up a protective layer, similar to scar tissue, at the sensitive area, which allows leaves to fall at the right time.
However, this year’s sudden change in temperature meant the layer wasn’t hardened up yet when the tree shut down.
“Spring and fall are high energy times for a tree,” Newsham said.
“I expect there will be some tree damage, especially to trees not natural to Alberta, such as ash.”
He said leaves may not drop at all this winter, and there may be die-back on the tips and small branches.
