seeing more pollen in the air? it's probably trees reacting to the drought last year
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seedlings from poplar and cottonwood trees, blow in the air in north-end dartmouth on june 10. last year's drought has caused trees to over-produce seeds and pollen this year as a natural response to the harsh conditions in 2025.
tim krochak
/
the chronicle herald
if you think you’ve been seeing more pollen in the air, tree seeds on the ground and whirly maple samaras — more commonly called helicopters — flying through the air this year, you’re probably right.
that’s because many types of trees are probably over-producing pollen and seeds in response to the drought conditions last year that dried out forests, woodlands and trees around homes.
healthy trees want to grow, while stressed trees often reproduce to help ensure the next generation.
natural events such as drought, fire and wind damage can weaken and stress mature trees and make them more susceptible to pests and disease. that stress can trigger trees to reproduce more to help ensure regeneration if mature trees are later affected by these threats.
“the drought is the most likely culprit here,” said simon bockstette, a senior planning forester with the province’s department of natural resources.
he said many tree species naturally produce a bumper crop on a regular basis. in the case of white spruce, that is every seven to 10 years. he said this is a natural response that helps promote regeneration and germination.
maple samaras — more commonly called helicopters — fill the end of a tree branch.
ian fairclough
/
the chronicle herald
that is called a mast year for many trees.
“that’s a natural way they tend to reproduce,” bockstette said.
“you could think about it as saving up some energy. rather than producing a small number of offspring every year and then having that eaten by herbivores and so on, their strategy is to save up some energy and produce a big crop, increasing the chance some of their offspring will can make it into the (tree) canopy.”
when it comes to stress events like drought, trees will produce a large amount of pollen and seeds because they were unable to take up water and absorb nutrients normally.
“that is sort of an evolutionary strategy to kind of hedge your bet as a tree,” bockstette said. “there’s a chance that something like (the drought) could be extended. sometimes they’re multi-year droughts, so the tree reproduces at a (higher rate) as an insurance policy.”
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he said the drought likely affected trees from one end of the province to the other, and those at higher elevations were most susceptible.
most of the pollen floating around now is from pine trees, he said, while that from hardwoods was earlier in the year.
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