A sweet, sugary scent tickles your nose, then disappears. It’s a quiet morning at the Arnold Arboretum in Jamaica Plain. A few dog walkers and joggers are making their way through the park and every view is like a scenic painting. In another breath, the scent is back again.
Baked apple pie, burning leaves and pumpkin spice are scents usually associated with the fall. Not cotton candy. But it's only in autumn when Cercidiphyllum japonicum, known as the katsura tree, emits a sugary scent.
“Burnt brown sugar, cotton candy. Other people smell different things, different noses, different things,” said Michael Dosmann, curator of living collections at the Arboretum. In German, he says, the tree is called "kuchenbaum," which translates to “cake tree.”
Dosmann, originally from Indiana, has been interested in the katsura tree since he was a teenager. He has worked extensively on a cultivation project which brings the trees from their native grounds in Japan and China, where they are under threat, and regenerates them at the arboretum, a process that can take 20 years to complete.
The saccharine smell can be traced to the chemical compound maltol, Dosmann explains, which is found in the tree’s leaves and is expressed in the air. “It’s just when the leaves are starting to go through their color change and drop off,” he said, adding that it’s unknown if there’s any evolutionary advantage.
The trees are located in various spots throughout the park, but a notable cluster along Linden Path is the ideal spot to try and catch the scent. An interactive map of the landscape can help you find their exact location.
Some of the oldest growing katsura trees, with wide and winding multi-stemmed trunks that twist into each other, date back to 1878. Younger trees, planted in 2007 and 2008, have smaller trunks and a more composed shape. All have heart-shaped leaves that gradually turn an apricot yellow this time of year.
“It’s funny to watch people walk by those trees. I’ll sometimes sit by the benches and you’ll see people smell it and they’re wondering where that smell is coming from," Dosmann said. "They’ll wonder if we’ve got a vendor someplace nearby selling cupcakes."
It’s only in these next few weeks that you’ll be able to catch the katsura tree scent. Like a leaf quietly falling to the ground, it may momentarily linger in midair, but in a fleeting moment it's gone.
This program aired on October 4, 2013. The audio for this program is not available.