|A row of ragweed sprouts next to one Cosmos seedling.|
|Cosmos seedling has a few lateral rootlets off the primary root.|
|Ragweed has long shallow root with rhizomes.|
|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.