I believe this is what I found in my pasture. It has begun to take off overnight. I do keep horses in this field so what is a safe herbicide to get rid of this weed. I realise I may have to move horses off it for a little while. But I don't have the option to keep them off of it for a whole season to completely replant. Need the best solution for a speedy fix. Also way to many to just hand weed.
We have a few different species of buttercup in Kentucky. Some are annual (reproduce from seeds) and some are perennial (return from roots each year and also produce new plants from seeds). They make their main growth in late fall and then again in late winter and early spring. They are often found where pastures have been overgrazed and/or where good forage grass is thinning. Buttercups and other weeds colonize when there is bare ground available for them to germinate and out-compete desired forage grasses.
We are already past the recommended herbicide spray window for effective control. You may be able to mow to prevent seed formation if buttercups are still flowering. My guess is that some viable seed have already formed. A good plan is to test your soil to check nutrient levels to see if fertilizer is needed, and then be ready to reseed the pastures in late August through September with desired forages. Thickening the good forage grass will help suppress future weed populations -- spraying will likely be necessary, though, next February - March.
I'd be happy to talk with you and/or make a site visit to help. Give me a call at 502-222-9453.