Something to Sneeze At

by Madeline Bodin

In the beauty pageant of Vermont and New Hampshire wildflowers, ragweed certainly won't win any titles. Problem is, it won't win Miss Congeniality either.

Until recently, most people considered ragweed merely the dullest member of the great late-summer bloom of composite flowers that includes goldenrods and asters. It was goldenrod that took the blame for the hayfever of late summer and early fall, even though ragweed was the guilty party.

I remember a boy bringing my third grade teacher a bouquet of goldenrod. She was not pleased.

"It's just that I have hayfever," she stammered as she banished the bouquet to the farthest corner of the classroom.

Eventually ragweed's secret got out, and people realized that it wasn't goldenrod causing those itchy, watery eyes or those runny noses. Goldenrod flowers are that brilliant, schoolbus yellow to attract pollinating insects. The insects carry the goldenrod pollen from flower to flower, leaving our human noses out of the equation.

Ragweed flowers, on the other hand, are green or yellow. The flower heads hang down as if they are embarrassed by their drab attire and hope to escape notice. They don't use flashy color, a sweet scent or an attentive posture to attract passing bees. Ragweed flowers are pollinated by the wind.

Their strategy involves massive amounts of pollen cast to the blind, insensible wind. Because ragweed is so common, and because it cranks out so much pollen, the pollen actually finds its way from one ragweed flower to another by chance. Of course, some of it finds its way to other places, including our human noses.

Blame ragweed pollen's particularly irritating shape (it's got spikes), or the fact that it's in your nose and there's plenty of it -- but either way, some people's bodies react to the irritation by revving up their immune systems, complete with sneezing. (Ah-choo!)

There are 17 species of ragweed in North America, but two species create most of the pollen: common ragweed and giant ragweed. Ragweeds are in the composite family of flowers, which means each thing that looks like a flower is actually dozens of tiny flowers packed together. Other composites are asters, dandelions, daisies and the newly paroled goldenrods.

If, in the middle of a hayfever attack, you decide that ragweed is some sort of evil invader, the plant version of the feared snakehead fish, well, let's blame the histamines. But ragweed is a native plant.

If you are the vindictive type, you will be pleased that ragweed has been naturalized in Europe. Europe may have given us dozens of pesky alien plants such as purple loosestrife and dandelions, but we have given Europe itchy eyes and runny noses.

Here in North America, ragweed plays its role in the ecosystem, and no, that role is not to sell allergy medication. The caterpillars of the Gorgone checkerspot butterfly, native to the American Midwest, find all the plants in the composite family tasty and consider ragweed leaves a superior lunch. Come fall, seed-eating birds belly up to the ragweed's all-you-can-eat seed buffet. Native Americans have a variety of medicinal uses for ragweed, including using the crushed leaves to relieve the itch of insect bites.

If ragweed is so normal and natural, why are we sneezing our heads off? Perhaps it's because there is more ragweed pollen these days.

Lewis Ziska, Ph.D., of the US Department of Agriculture, performed two experiments. First, he grew ragweed plants under controlled conditions that mimicked the amount of carbon dioxide in the atmosphere a century ago, the amount of carbon dioxide in today's atmosphere, and the amount of carbon dioxide predicted for the year 2100. Carbon dioxide is the stuff we exhale, but we've got more of it around these days because of deforestation and the burning of fossil fuels. (No, holding your breath won't help.)

Ziska found that the amount of pollen the ragweed plants produced nearly doubled when the amount of carbon dioxide changed from the levels of a century ago to the levels of today. The amount of pollen doubled again under the amount of carbon dioxide predicted for 2100.

In a recent study he grew ragweed in a city, a suburb and a rural area. He found the urban ragweed, exposed to higher temperatures and higher levels of carbon dioxide, grew faster and produced more pollen than the ragweed grown in the rural area.

"Cities already have significantly higher temperatures and carbon dioxide -- about what the rest of the world will experience in 40 to 50 years according to the IPCC [Intergovernmental Panel on Climate Change]," Ziska explains.

If the trend in increasing carbon dioxide levels continues, there will be only one thing to say when ragweed season rolls around each year: bless you!

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