Sunday, April 11, 2010

Why we're sneezing more these days

From the NY Times:

Street trees weren’t always as allergenic as they are today. Back in the 1950s, the most popular species planted in the United States was the native American elm, which sheds little pollen. Millions of these tall, stately trees lined the streets of towns and cities from coast to coast. Sadly, in the 1960s and ’70s, Dutch elm disease killed most of the elms, and many of them were replaced with species that are highly allergenic.

This has caused trouble for Americans with allergies — as many as 30 percent of adults and 40 percent of children — most of whom are sensitive to pollen, as well as for the many millions who have allergy-induced asthma. Although some pollen can be carried great distances by the wind, most atmospheric pollen comes from plants growing nearby. In other words, the pollen that’s making you sneeze as you walk down the street probably came from the tree you just passed. So it makes sense for gardeners, especially public gardeners who plant trees by the dozens, to pay attention to the pollen their trees produce.

Some trees shed huge amounts of highly allergenic pollen; others produce very little, or their pollen is only moderately irritating. Female plants produce no pollen at all. But arborists rarely take this into account. In New York City, street trees are selected only for their hardiness in winter; their resistance to disease, insects and drought; their ability to withstand smog; and their size, shape and color.

The pollen that causes the most severe allergic reactions comes from a few so-called monoecious species of trees, which have both male and female flowers, and from the males of separate-sexed (dioecious) species. Many arborists and landscapers like to plant male trees and shrubs because they’re “litter-free” — that is, they produce no seeds or seedpods. But male trees shed lots of pollen; that’s their job. And once it’s released, it can be blown around for months.

In New York City, about 30 percent of the street trees are Norway maples and London planes, both monoecious kinds that always produce allergenic pollen.

Photo from Solar One


DebbyBruck said...

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Anonymous said...

I'd rather have the trees then not because of some pollen. Outside of the city people seem to manage just fine with whatever trees are around.

Anonymous said...

An excellent explanation on pollen especially on why there are differences in the effect of allergies affecting people years ago and today!

Anonymous said...

The tree pits in Astoria are a complete joke:

1. all the trees on one block are the same species.

2. the pits are so large they can take in three trees.

3. the pits are too close together.

this is what happens when you put politicans with the smarts of postal clerks in charge of tree planting.

Anonymous said...

This is nothing to sneeze at!

Anonymous said...

Another important story highlighted. Many people in Queens I know have noted how they are getting more allergies and now we know the reason. The tree in front of my house was planted a few years ago. The DOP(/DOT) need to either stop planting these allergic pollen trees, or start planting a larger variety of trees.

Anonymous said...

Pollen doesnt bother me much. What DOES bother me is the trees with the white blossoms in the spring that smell like cat piss and semen.

Who the hell thoguht those would be a good idea????

Anonymous said...

I love trees. I love them during the summer because of their beauty and shade they provide. I love them more during autumn because of the different colors.

Oddly enough, my allergies bother me only during September and early October.

Anonymous said...

What DOES bother me is the trees with the white blossoms in the spring that smell like cat piss and semen.

What's wrong the the smell of semen?

Anonymous said...

Female trees at times are problematic too. The female Ginko Biloba produces a medicinal fruit with a smell that stops traffic.