Ask Sam: Why Is There So Much Pollen This Year?
Every other Friday on Morning Edition, NHPR’s Sam Evans-Brown tracks down answers to questions about the environment and outdoors for our listeners in a segment we call “Ask Sam.” Do you have a question you want Sam to tackle? Click here to submit it!
Virginia from Manchester asks: I was wondering if we are having an abnormally high amount of pollen this season. And if we are having a worse pollen season than usual, I was wondering what the reason might be?
Ah, pollen. Or as I like to call it (much to the dismay of nearly everyone around me) plant sperm.
(Ok, it's not actually plant sperm, but that's convenient short-hand.)
Asking about airborne pollen is like asking about the weather: there are very short term fluctuations - on the scale of differences over a few hours - but then there are big picture, long-term trends.
So what about the short-term stuff?
“A bad day for pollen is you go through a wet period, and then it dries out for a few days and that usually results in a much higher pollen count,” says Dave Samuel, Senior Meteorologist with accuweather.com.
Fairly straightforward, right? Rain followed by sun is good for plants, which means more pollen. That also sounds a lot like this spring as a whole, right?
The other thing that’s going on is that this spring was cold, the coolest since 2008 in many parts of the state. Which means that a lot of the plants that usually put out pollen in the spring were a couple weeks behind.
“I think what’s happening right now in 2019, is your seeing that we’re kind of having this apex of a lot of the tree pollen and also the grass pollen coming down at once,” says Michael Piantedosi, director of conservation at the Native Plant Trust.
In other words, while we usually get a fairly steady progression from tree pollen, to grass pollen, to ragweed season, this year we got a big spike of a couple varieties all at once.
And then there are the long term trends
Perhaps you’ve heard? The climate is warming. This means spring comes earlier, fall starts later and that longer growing season means a longer more intense, pollen season.
A big study of this just came out this spring, and found that all over the Northern Hemisphere, over the last 20 years or so we’ve gained an extra day of allergy season, and there’s on average 10 percent more pollen in the air during that season.
Carbon dioxide itself is also plant food, and more carbon dioxide can bump up growth rates of certain plants, leading to more pollen.
And let’s not forget the human factor
Have you heard of horticultural sexism? It’s a term promoted by Tom Ogren, a horticulturist out in California. It’s contributing to allergy symptoms for urban dwellers as well.
“If you were to walk down a main street in, say, the city of Boston, you’re going to find that the vast majority of trees surrounding people are male,” explains Piantedosi, “And the reason is we don’t want the fruit cluttering the streets. We don’t want more stuff we have to sweep up from our urban and suburban settings.”
Remember, pollen is basically tree sperm, blowing indiscriminately through the air in hopes that it will land in a flower, and so this preference for male trees by landscapers leads to increased pollen counts, especially in urban spaces.
So, Manchester dwellers, you can (at least partly) blame your sniffles on those urban tree-scapers!
Sam Evans-Brown, is host of NHPR’s Outside/In which you can subscribe to where-ever you get your podcasts. If you’d like to submit a question you can record it as a voice memo on your smartphone and send it to email@example.com, OR call the hotline, 1-844-GO-OTTER.