Monday, August 17, 2009

Ambrosia artemisiifolia: delcious-sounding name for a very annoying plant

Warning: this plant is considered a noxious weed under the Ontario Weed Control Act.

[Photo: Ambrosia artemisiifolia in bloom, High Park.]Such a lovely-sounding name for this plant with such pretty, fern-like leaves! (click the photo to get a better look) If only it weren't for the flowers...

In case you haven't recognized this common but easily overlooked plant yet, it's better known as common ragweed (petite herbe à poux). Those boring little green flowers have no interest for animal pollinators, so ragweed instead releases massive amounts of lightweight pollen into the wind, relying on the sheer quanitity of pollen to ensure that some of it will reach a female flower and fertilize it. (Separate male and female flowers are produced on each plant.)

Ragweed grows in the same habitats and blooms around the same time as its showier cousins, the goldenrods (verge d'or, Solidago spp.). Because ragweed is so inconspicuous, goldenrod is often unfairly blamed for ragweed pollen allergies. In fact goldenrod pollen is too heavy to be wind-borned; that's why it has those gorgeous flowers, to attract the insects needed for pollination.

According to Wikipedia, the genus name Ambrosia comes from the same root, άμβροτος, as the ambrosia which is the food of the gods, but this root word actually means "immortal", referring to the difficulty of eradicating this plant. (This species is actually an annual, so not immortal by any means.)

Ragweed is one of the top 10 herbacious plants to feed wild birds, because it produces numerous, oil-rich seeds. However, given how many people are allergic to it, I think it should be kept to wilderness areas far from humanity, certainly not in Toronto gardens.

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