Mystery plant 034

This plant — considered an invasive weed — can be found throughout North America and Europe.  Please identify it (both its common and scientific names) in a comment and share any personal experiences you have with this plant.


Group of young plants


Varying leaf shape


Leaf arrangement along stem


Top leaves and developing flower raceme


Expanding flower raceme


Close view of developing staminate (male) flowers along raceme


Staminate flowers in bloom


Pistillate (female) flowers along stem — below staminate flowers


Flowering racemes


Tops of mature plants (in foreground)


ANSWER (subsequently added to this post to facilitate the “search” function for these images):  Great ragweed (Ambrosia trifida)

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4 Responses to Mystery plant 034

  1. Richard Lewis says:

    Ambrosia trifida, Giant Ragweed. Not as common here in central New York, as the Common Ragweed (Ambrosia artemisiifolia). Thanks for contest!

  2. Joyce Hochsprung says:

    Ambrosia trifada, Giant Ragweed, a member of the aster family. It has been showing up up in my area more frequently the last couple of years and it appears to be developing resistance to glyphosate.

  3. Mike Krebill says:

    Richard and Joyce are right, and Richard spelled the species name correctly: it is Ambrosia trifida, Giant Ragweed. It is a sandpaper rough, tall, hairy plant very common in disturbed ground and along the edge of woods in floodplains in the Midwest. The common name is appropriate. Found one near a bridge over the Des Moines River in southeast Iowa in 2008 that measured 14′ 9″ tall. When we were kids, my friends and I used the dead stalks for spears.

  4. Angelyn says:

    Yes! This is Great ragweed — or Giant ragweed — which has the scientific name of Ambrosia trifida. Thanks for sharing your personal experiences with this plant. Mike, 14’9″ is awfully tall. I can see why you would have measured it.

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