Q: This weed is nasty. If you touch it, it doesn’t stop stinging for 4 hrs.
It came to our pasture in hay from south Georgia. It has jumped from one small spot to several large ones. I tried 2,4-D and I’m just amazed that I can’t even kill it with Round-up.
It’s like playing ‘whack-a-mole’ in the pasture!
A: This is a case where knowing your foe exactly is paramount.
The weed has been identified as fireweed, Urtica chamaedryoides. It is a winter annual, meaning it sprouts from seed in October and disappears by June each year.
As you have found, fireweed is resistant to both 2,4-D and to glyphosate (Roundup). Both of these products normally do a good job controlling broadleaf plants, but not this one.
The best control is to use the specific pasture herbicides Remedy, PastureGard, or Milestone. Your local feed ‘n’ seed will probably have to order the weed killers for you.
See an article on control at: Fireweed – Control in Pastures