If you are allergic to ragweed you are probably aware it has started blooming now. Unlucky goldenrod (Solidago spp.), pictured here, gets blamed for fall allergies, but for most people it is really caused by two species of ragweed.
Goldenrod's attractive flowers attract insect pollinators, and the grains of pollen are large enough to stick to insects. They don't tend to blow in the wind the way wind-pollinated ragweed pollen does. Ragweed blooms at the same time as goldenrod, though, so showy goldenrod gets wrongly blamed.
Ragweed's flowers are inconspicuous because they don't need to attract insects; the light pollen is carried by the wind, as you already know. If you bump a plant in full flower, a cloud of pollen puffs out.
There are two species of ragweed common in our area, giant ragweed (Ambrosia trifida), which grows eight feet tall or more and has some three-lobed leaves; and common ragweed (Ambrosia artemisiifolia) which is half as tall and has deeply-cut leaves. The botanic names refer to the leaves, with the latter having leaves like an artemisia, or wormwood plant.
I don't know how to relate the genus name—Ambrosia—with the common definition of the word ambrosia: "something extremely pleasing to taste or smell." This plant causes me no shortage of misery in bloom (though it is a good wildlife plant).
And our allergy suffering is likely to get worse: recent research by Lewis Ziska at the USDA Crop Systems and Global Change lab has shown that in the presence of additional carbon dioxide—a condition that the world in general and cities in particular are experiencing—ragweed plants grow taller, produce more pollen, and each grain of pollen has a larger amount ot the proteins that stimulate an allergic response in some people. He presented this and other research at the Invasive Plants conference last week at University of Pennsylvania.
So avoid ragweed if you can, shower before retiring, and keep your outdoor clothes out of your bedroom, and you might sleep a litttle better.
