Continuous grazing of the plants prevents that natural dormancy from happening and weakens the plants. Broadleaf weed seeds germinate more easily as the grass grows thinner. These weeds further weaken the grass by competing for water and nutrients. That usually means spraying around the end of April, when the grass is thick and lush and you don't think you have a weed problem. Spray for broadleaf winter weeds the end of November.
Herbicides are much less effective once they have begun to head out.
Bushhog the pasture after heading begins to prevent the weeds from going to seed. A good fescue stand will have 40 to 60 seedlings per square foot by November. This will thicken up to provide 90 to 100 percent ground cover, shade out germinating weeds, and produce high yields in favorable weather conditions when managed properly. 4 to 9 inches apart. Drilling concentrates the seeds within a furrow.