An excruciating winter, a savage ice storm and the coldest March in 30 years mean Toronto’s trees are still lying dormant, holding onto the airborne pollen that curses allergy sufferers.
“It is very slow this year, obviously — nothing’s happening, which is really unusual,” said Frances Coates, a microbiologist and the CEO of Aerobiology Research Laboratories.
The Ottawa company has 30 pollen monitoring stations across the country, including one near Queen’s Park in downtown Toronto. Normally, their equipment would begin capturing the airborne grains around March 10, Coates said. But not this year.
“We’re early April and very, very little has happened, if anything at all,” Coates said.
But those who fall prey to pollen should not be lulled into a false sense of security. As the sun beats down and the soil thaws, the trees will wake from their slumber.
In the U.S., the Washington Post has dubbed the impending release of all that pent-up pollen the “pollen vortex,” warning allergy sufferers to prepare for a surge of sniffling as delayed trees and grass pollinate all at once. Canadian experts are more cautious.
“It all depends on how quickly it gets warm,” Coates said. “If the temperatures get warm and stay warm, the season is going to happen fairly quickly for some of the trees.”
Pollen arrives in waves from different species of trees and grasses. Poplars, maples and elms are all early bloomers. Pines, oaks and ash trees arrive later in the season, so they aren’t as thrown off by the cooler weather.
Coates anticipates the pollen season may be slightly prolonged but not as severe for the early trees. It’s too early to tell how the later trees will be influenced by the cold winter, she said.
“It’s a late start, but it doesn’t mean we’re not going to have a robust pollen season,” said Dr. Susan Waserman, an allergist at McMaster University’s department of medicine.
In order to start pumping out their pollen, trees need several days of temperatures above 6 degrees Celsius, Waserman said.
Environment Canada says those temperatures could arrive in the coming days, which see daytime temperatures edging up but still a few degrees cooler than usual at this time of year.
“We’re going to have more opportunities for those buds to tentatively start coming out, but I think everything is going to be a little slower this April than it has been in past years,” said Geoff Coulson, a Toronto-based meteorologist with Environment Canada.
The devastating ice storm that mutilated up to 20 per cent of Toronto’s urban forest may have a lasting effect: toppled trees can’t produce pollen.
In some cases, though, a wounded tree may actually release extra pollen to make up for its missing branches, a last-ditch attempt to reproduce before it dies.
“Unless the whole tree is dead, the tree will compensate by releasing a whole lot of pollen,” Coates said. “It’s just a matter of survival.”
Considering the sheer number of plants in the Toronto area and the distance pollen can travel on the wind, Waserman said she doubts the ice storm will put any significant dent in the number of clinical cases of allergy sufferers.
This year’s cold-induced pollen delay may seem like an anomaly, but it could be part of long-term weather fluctuations affecting allergy seasons everywhere.
Scientists have documented that in many parts of the world, the allergy season starts earlier and lasts longer each year, potentially because of climate change. Researchers have theorized that the more carbon dioxide in the atmosphere and the warmer the temperatures, the more plants produce flowers or food, which means more pollen.
The spring ragweed allergy season has lengthened by up to 27 days since 1995 depending on where you are in North America, according to research by the U.S. Agriculture Department published in the Proceedings of the National Academy of Sciences in 2011.
Higher latitudes are warming faster than those closer to the equator and are seeing proportionally longer pollen seasons, according to that study. For instance, in Saskatoon, the season was 27 days longer than the usual 44 days. By contrast, the effect in places such as Texas was minimal.
But Coates cautions that given all the factors that play into pollen production – rainfall, temperatures, the pollen cycles of individual species – nobody can say for sure how much pollen will fill the air, and how miserable the spring will be for allergy sufferers.
“We have to wait and see what kind of spring — if it ever comes — we have,” she said.