Harry from Mo writes
This article from the Kentucky Extension has great information about how to control ironweed in pastures. You can check with your extension for advice on the exact timing in your area, but I imagine it will be similar to this. In August or by early September apply a pasture herbicide containing either triclopyr (eg. PastureGard, Crossbow, etc.) or aminopyralid (eg. GrazonNext, etc.) as a broadcast treatment. Although mid-summer (June and July) treatments can provide good control, better herbicide movement to the root system occurs with perennial weeds such as tall ironweed with late summer applications. I'm not sure how large of an area you need to treat, but Gordon's Pasture Pro is labeled for Ironweed and good for smaller applications. PastureGard HL can be used on hay as long as you do not harvest the hay within 14 days after application. You would use 1-1.5 pints per acre for perennial broadleaf weeds. GrazonNext is labeled for ironweed as well, but the haying and manure restrictions for this product are very strict, so I always encourage folks to review these restrictions very carefully before purchasing or using this product.
Answer last updated on: 07/25/2022