Ragweed season officially began August 15 and runs through September. I’m not allergic to it, but those of you who are may want to know the enemy and learn how to avoid it.
First, a primer on what is NOT ragweed.
Goldenrod is not ragweed. Ragweed (Ambrosia sp. on left) is a wind-pollinated plant with green flowers on thin spikes. Goldenrod (Solidago sp. on right) is a bee-and-butterfly pollinated plant with yellow flowers in a feathery plume. Don’t worry about those yellow flowers. Goldenrod is not busy spreading pollen; it’s busy attracting bees.
Ragweed (Ambrosia genus) is a member of the Aster family native to the Americas but now spread to Europe. The most common species in Pennsylvania, common ragweed Ambrosia artemisiifolia, grows easily by the side of the road and in disturbed places. It doesn’t stand out.
Common ragweed’s female flowers are nearly hidden in the leaf axils and pollinated by the wind.
The male flowers are the ones to worry about. Perched on spikes, facing downward, and loaded with pollen, a slight tap is all it takes to release a cloud of pollen. Imagine what the wind can do!
A single plant may produce about a billion grains of pollen per season, and the pollen is transported on the wind. It causes about half of all cases of pollen-associated allergic rhinitis in North America. … Ragweed pollen can remain airborne for days and travel great distances, affecting people hundreds of miles away. It can even be carried 300 to 400 miles (640 km) out to sea
It’s hard to avoid these pollen grains because they’re so pervasive, but you can be forewarned of a bad pollen day at pollen.com. On the other hand, your nose might know before the website does!
Meanwhile, don’t walk past this plant unawares. Here’s what it looks like in a weedy patch.
Know your enemy.
(photos from Wikimedia Commons; click on the captions to see the originals)
(*) Different species of goldenrod have different flower cluster shapes — it’s not always a plume. However tall goldenrod, pictured above, is the one most often called ragweed by mistake.