By David Schout
As hay fever season looms, we’re being told to go easy on the humble London plane tree, which despite popular belief isn’t to blame for runny noses, itchy eyes and sneezing.
For those that live or work in the CBD, there’s every chance you’re all too familiar with the London plane, a tree which accounts for a whopping 70 per cent of the Hoddle Grid’s urban forest.
Known for its resilience to warm weather and the tremendous shade it provides in the hotter months, the trees are synonymous with Melbourne.
Perhaps lesser known, they are also extremely efficient at absorbing air pollution owing to their large leaves.
But in the months of October and November in particular, the trees are cursed by many Melburnians as the root cause of highly irritable (and sometimes debilitating) hay fever symptoms.
“I’m thinking of starting up a vigilante group committed to razing every plane tree in the CBD,” one Twitter user said last spring. “Hay fever sufferers of Melbourne unite!”
“All those in favour of cutting down every plane tree in Melbourne, sneeze bitterly,” another said.
But have we got it wrong about the poor old London plane?
The City of Melbourne says we have.
“(The trees) are often inaccurately associated with hay fever,” council environment portfolio chair Cathy Oke told CBD News.
“While some people may experience physical irritation from plane tree trichomes (leaf and shoot hairs), the most common cause of hay fever is grass pollen.”
When the trees’ trichomes are released they can be particularly messy in the CBD, something that is worsened on windy days.
Their visible, swirling presence leads many to blame them for the onset and exacerbation of hay fever symptoms.
But while they can be irritable, it’s grass pollen that’s the primary issue.
“The shedding of plane tree trichomes occurs during the same period that grass pollen levels are highest in Melbourne and it is common for sufferers of hay fever to associate their symptoms with the trichomes,” Cr Oke said.
Associate professor Ed Newbigin, a plant biologist from the University of Melbourne and coordinator of the Melbourne Pollen Count, confirmed we should be predominantly shifting our blame to grass pollen.
“I have been counting grass pollen in Melbourne for over 20 years and can attest to it being a major driver of springtime allergies,” he said.
But he said that he couldn’t completely rule out plane tree pollen as a cause of hay fever as the Melbourne Pollen Count predominantly measured grass pollen.
Rather, he pointed to a 2007 study in Sydney that found less than a quarter of people were allergic to plane tree pollen, despite it making up over three-quarters of the air’s total pollen.
This was contrasted with over half of those tested who were allergic to grass pollen.
So, while we can’t say that plane trees don’t cause issues for hay fever sufferers, their impact is far less than we might think.
Whatever the case, the council has pledged to significantly reduce the CBD’s high number of London plane trees in coming years in the face of unprecedented climate change, population growth and urban heating challenges.
“We want to increase diversity in our urban forest and have a target of no more than five per cent for any species within the municipality,” Cr Oke said.
“The changes are already underway. We’re replacing existing trees with new species progressively as the opportunities arise. Plane trees have already been replaced on Flinders St between Fed Square and Wellington Parade South, with lemon-scented gums.”