Q: I have a plant I need you to identify. In early May I noticed it was about 6-8 inches tall. It had an interesting leaf pattern. It is now (in June) more than five feet tall. Any idea on what it might be?
A: I know this plant well! My family farm had a huge patch of it beside the barn where bantam hens hid their eggs. When we boys would find a nest, we’d steal the eggs and throw them at each other. What fun!
The plant is ragweed, Ambrosia artemisiifolia. Despite the name, this plant is not sweet. It is a weed of highest order: hard to get rid of and producing severe allergic reaction in lots of people. When goldenrod blooms in fall, ragweed is also blooming. Goldenrod gets all the blame for causing sneezes and sniffles but ragweed is actually to blame.
I wouldn’t keep it in your garden if you or any neighbors have allergies.
The easiest way to control it is to pull it out of the ground when seen. The roots are not extensive.
You could also spray patches of the weed with glyphosate (click for sources).