Field of Science

Weed of the week - ragweed

Your eyes may have just started to water just looking at these images of giant ragweed. The plants can reach 7-8 feet tall easy and a local walking/bicycling trail goes through a virtual gully of them just now coming into bloom. There are so many flowers they'll leave a yellow dusting of haploid males (pollen) on the ground.  Woe be to any allergic people who hazard this gauntlet.  Both the common and giant ragweeds are easy enough to recognize, but they are usually ignored in the spring when they are more easily controlled by mowing them down or whacking them out, or by herbicide application in the spring or early summer.  Too late now.  The smaller common ragweed showed up in an older blog and you will notice the highly lobed leaves that Linnaeus thought resembled wormwood, thus Ambrosia artemisiifolia.  Notice that the giant ragweed has three lobed leaves Ambrosia trifida (shown above) and the flowers are not showy at all because it's wind pollinated, so the co-flowering goldenrod gets the blame for hayfever. The flowers shown are just prior to flowering.  How long can you hold your breath?  

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