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| A row of ragweed sprouts next to one Cosmos seedling. |
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| Cosmos seedling has a few lateral rootlets off the primary root. |
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| Ragweed has long shallow root with rhizomes. |
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| Ragweed on the left, Cosmos on the right. Don't confuse the two! |
Last summer I let a young plant grow in my flowerbed. It
looked to me like a Cosmos (C. sulphureus) seedling. When I noticed it again, it was not a
beautiful, glowing Cosmos, but a mature ragweed. I pulled it up, of course, but too late. This February, I had hundreds of little
ragweed babies popping up in that flowerbed.
Arrgh!
To be sure I would never make the same mistake, I took these
photos of a cosmos seeding next to the ragweed sprouts. I might still confuse the foliage, but there
is NO WAY that I will mistake what happens under the soil with the roots! The Cosmos seedling has only a small set of lateral
rootlets of the primary root. The ragweed has a clever, extensive
underground system of threadlike roots and rhizomes that supports multiple
plants. To get it under control, I dig
up each bit of ragweed and collect as much of the root system as possible. I declare that this flowerbed will eventually be ragweed free.
9 comments:
Thanks for posting this. This is my first year to grow cosmos, so I was wondering how to tell it from weeds. Now I know.
Hello Cristy! I am glad to hear that this was useful. I figured I could not be the only one who had trouble telling these guys apart. We love cosmos - so many butterflies and bees use it for nectar. You'll be able to save seeds for next year, too.
Thank you soo much! I had a friend give me "mystery" seeds, I am highly allergic to ragweed but love flowers, so when I seen this growing in my flower beds, I got nervous and started looking for any info I could. The foliage is so similar I had already pulled a few but now I see I have pulled my flowers :-( Will definitely be more careful next time! Glad I didn't pull them all!!
I'm writing 3 years later, but I'm still having trouble distinguishing them without uprooting them. I think the leaves are much denser on the ragweed, but it is still strange to me how similar the foliage is. Also how different this giant cosmos looks compared to "regular" cosmos plants, which are so feathery.
I had a severe allergy attack after stupidly pulling up what I now know is ragweed with my bare hands. My entire face puffed and swelled. My eyes were almost swollen shut. Thanks for posting this...that rooted vine was exactly what did me in.
Same confusion here until I realized the branch structure on cosmos is opposite but it’s alternate on ragweed (after the first couple of branch sets grow, it’s easy to tell. I think very young ragweed has a couple of opposite branches early on. )
I think the cosmos leaf is a slightly lighter shade of green. But hard to tell unless they are side by side.
You mean to tell me I've been pulling up my Cosmos because I thought they were ragweed? Rookie.
I took photos today of the many transplants I made of presumed cosmos—as the seedlings came up where I had planted them in early late winter/spring And uploaded them to iNauralist for ID. I was wondering as there were similar plants by the north side of the barn. iNaturalist identified them as ragweed. I think I will wait until they get bigger. Roots are singular when I transplanted them.
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