Marvin Pritts, a horticulture professor at Cornell University, explains why allergies are exceptionally bad this season and warns that while the rain provides temporary relief, it also promotes weed seed germination which will contribute to higher levels of pollen later this summer.
“In a year with a long, cold winter, flowering – and the shedding of pollen – is compressed. This year, there is overlap between the shedding of tree pollen and the beginning of grasses flowering. Individuals sensitive to both kinds are getting a double-whammy of sorts. Fortunately, the recent rainy weather will wash out pollen from the air, and provide some temporary relief. Also, the shedding of tree pollen is mostly over.
“While the rain is providing temporary relief, it promotes weed seed germination so it may contribute to higher levels of pollen later in the season.
“People often associate seasonal allergies with a specific flower that they see in bloom during that time. In most cases, individuals are not exposed to the pollen from showy flowers. Such flowers are attractive to insects so their pollen is sticky and is not carried by the wind. So, when allergies begin to rise when the goldenrod flowers, it is not the goldenrod pollen causing the allergic reaction but rather the ragweed with its inconspicuous flowers shedding wind-borne pollen at the same time.
“Typically trees are the first plants to shed pollen in spring. They don’t have to grow to become reproductive, so most take care of reproduction first thing when the weather warms. This is followed by the flowering of perennial grasses that have to grow somewhat to become reproductive, but they already have a well-established root system from which to support their flowers. Lastly come the annual plants, like ragweed, that have to germinate and grow to a mature size before becoming reproductive and shedding pollen.”
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