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The Pollen Section

Trees that Make You Sneeze

Allergic Living’s handy region-by-region field guide to Canada.
For the U.S. field guide, see America’s Trees of Allergies.

WE CAN blame the deciduous trees’ attempts at procreation for our watery, red-eyed snuffling and other springtime rhinitis symptoms. Catkins, which often appear as elaborate cones or buds, are a tree’s reproductive organs, and they bloom before the leaves bud. Male catkins will release literally millions of pollen grains into the air in an attempt to find a female catkin match.

Dr. Wilf Nicholls, director of the Memorial University of Newfoundland Botanical Garden, explains that wind pollination is “super inefficient” because only a fraction of the huge amounts of tiny grains the tree churns out will arrive at their intended destination, the female catkin. Instead, great quantities of them will be inhaled into noses and throats and set off reactions in the tree allergic.

It’s an unlucky break that most deciduous trees in northern climes are wind-pollinated. Birch, elm, maple, oak and poplar are some of the most allergenic trees across Canada and the northern United States. But where you are, the month and the weather all influence the onset of symptoms.

West Coast

On the foliage-rich west coast, red alder is public enemy number one. Robert Guy, head of forest sciences at the University of British Columbia, says much of the forest surrounding coastal towns and cities is full of red alder. Depending on the weather, these trees can pollinate as early as mid-February, or as late as the end of March, and they spread pollen for about three weeks.

Vancouver allergist Dr. Donald Stark says red alder is particularly insidious because it produces a ton of pollen; it often has the highest pollen count of any plant on the coast. People allergic to it may also react to birch trees, which pollinate about a month after alders, prolonging the misery.

Stark identifies the Garry oak as another culprit on the west coast.
In most of Canada, ragweed is the worst offender for triggering hay fever, followed by grass, then trees. Stark says the west coast is the exception: here, trees pack the hardest punch.

Next: Traveling Eastward

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Allergic Living acknowledges the assistance of the OMDC Magazine Fund, an initative of the Ontario Media Development Cooperation.