Friday, September 6, 2013

What Causes Hay Fever? "Not I" says the Goldenrod.

In late Summer and early Fall fields and roadsides in Mid-Michigan are covered with several species of Goldenrod (Solidago spp.).  Goldenrods are large showy wildflowers that grow in a wide variety of habitats from coastal dunes, to pine barrens, prairies, old fields, oak savannas, woodlands, and wetlands.  Different species grow in soils that range from wet to dry. 

Canada Goldenrod (Solidago canadensis)
Lance-leafed Goldenrod (Euthamia graminifolia -formerly Solidago graminifolia)

Blue-stemmed Goldenrod (Solidago caesia)

Zigzag Goldenrod (Solidago flexicaulis)
Usually about the same time that the Goldenrod starts to bloom many people begin to suffer from Allergic Rhinitis or "Hay Fever".  Hay Fever is an allergic reaction to airborne pollen.  Symptoms of Hay Fever may include congestion, a runny nose, itchy/watery eyes, headache, an itchy throat, and sneezing.

So does Goldenrod cause Hay Fever?


Like most showy species of flowers, the pollen grains from Goldenrods are much too large to be airborne.  Instead they are carried by bees, flies, wasps, and other pollinators.  Plants with large showy flowers have developed them specifically to attract pollinators.  By enlisting insects (and other pollinators) to perform pollination, these plants have increased the likelihood that they will be successfully pollinated.  Even if a person is allergic to Goldenrod pollen the odds that any of that pollen will find its way into their nasal passages are very small.

So what is the cause of Hay Fever this time of year?

The most common culprit is Annual Ragweed (Ambrosia artemisiifolia).

Annual Ragweed (Ambrosia artemisiifolia)

Annual Ragweed (Ambrosia artemisiifolia)

Plants that rely on the wind for pollination typically have small flowers.  The male flowers of the Annual Ragweed are located on the green spikes that rise above the plant.  Each spike is covered with dozens of small pale green flowers.

Flowering spike of the Annual Ragweed (Ambrosia artemisiifolia)

They produce large amounts of very small pollen.  They produce such large amounts of pollen because without the aid of pollinators, their pollen finds its way to other flowers by chance.  Some of that pollen also finds its way into human nasal passages.  If you are one of the approximately 20% of people in North America (or Western Europe) that is allergic to the pollen from Annual Ragweed you will develop symptoms.

So enjoy the beauty of Goldenrod plants and stop worrying that you are allergic to it.

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