Hello Again Tom,

As communicated in my response to your first question- applying herbicide to buttercup while it is in bloom will not yield high success for killing or suppressing it. The best time to treat buttercup with herbicide is in the early spring before it flowers or in the fall as it sends energy to the root system to store for the following growing season.

Ironweed control could be achieved at this time if the plants are still fairly small. As ironweed is not a toxic weed, the concerns about it tend to be more aesthetically linked rather than for concerns regarding animal intake. 

Given the description of your pasture challenges, I would encourage you to clip the pasture to knock ironweed growth back and to prevent additional buttercup seed from developing. I would encourage you to plan a herbicide application in September to treat newly germinated buttercup and do a follow-up application next March on buttercup as it breaks winter dormancy. 

Given appropriate timing of application, both products listed above should provide good control of both buttercup and ironweed. Option 1 will have fewer restrictions overall. Option 2 will have broader restrictions. These restrictions pertain primarily to hay making, moving hay, and manure. In general, herbicides with 2,4-D as the active ingredient require 7-days rest post-application before lactating animals can graze the pasture again.

Please fully read all product labels completely before purchasing and again before application to be sure all important information including grazing restrictions have been considered. Details may vary from one product to another- even with the same active ingredients. 

You can see more information on herbicides in pastures with grazing restrictions listed out in the attached PDF. 

You can also call your local Extension Office directly for localized assistance. 

Sincerely,

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Sure!

Depending on what equipment you have available, I suggest using a mower or bush hog to clip the areas with greatest week pressure to a height of about 4-6 inches. This should prevent most of the buttercup flowers from developing seed and knock the ironweed back in its development too, while still allowing good residual of desirable forage for it to regrow and be ready to graze again soon. You may want to repeat this process if you see more blooms as time progresses until you get to the ideal time to apply herbicide. You could apply herbicide to the ironweed and have decent success 1-2 weeks after clipping it back, when fresh new growth begins again.

Good question about if the clippings pose a risk. They pose less of a risk dry than they do fresh. In the case of buttercup, the compound that causes toxicity dissipates as it dries, and poses less danger in this state than fresh and growing.