Common Ragweed

Ambrosia artemisiifolia

Common ragweed plant
Common ragweed plant. Photo courtesy of Meneerke Bloem. Licensed under CC BY-SA 3.0.
Common ragweed is a widespread noxious weed which can be highly competitive with crops (especially soybeans). Unlike its cousin, the giant ragweed, the common ragweed grows to a height of only 2-4ft.
The first true leaves of common ragweed will already show the characteristic deep lobes, distinguishing them from giant ragweed.
Common ragweed seedling
Common ragweed seedling. Photo courtesy of John D. Byrd, Mississippi State University. Licensed under CC BY 3.0.
The leaves have several very deep lobes which distinguish them from the related giant ragweed. They grow alternately on the stem.
Common ragweed leaf
Common ragweed leaf. Note the deep lobes. Photo courtesy of Bruce Ackley, The Ohio State University. Licensed under CC BY 3.0.
Common ragweed is a a very competitive weed, particularly in its ability to absorb trace nutrients. This leaves the surrounding crop deficient, reducing yield.
Common ragweed can be controlled by many herbicides, although resistance has developed in some areas. Always read and follow all label instructions.