After the rains have returned, broadleaf weed herbicides should become effective. However, don’t be in too much of a rush to apply because our data suggests that better control is obtained with October applications in than in September. We found that herbicides applied from October 1 through November 1 improved long-term ground ivy control compared to the same herbicides applied in September. Our speculation is that weeds are killed either directly by the herbicide when applied later in the fall or weakened to the point that they succumb to winterkill. Herbicides applied earlier in the fall may allow the plant to recover and survive the winter. This was validated by researchers in Scottsbluff, NE, who found that applications of 2,4-D and/or dicamba were far more effective in controlling dandelions and Canada thistle when applied 1 to 10 days after the first frost than when applied 5 to 11 days before the frost. These researchers found that the herbicides indirectly reduced concentrations of total sugars, thus increasing the plants susceptibility to freezing temperatures and winterkill. We have found that even tough-to-control weeds can be controlled effectively in October and November with herbicides that would be considered marginal at other times of the year. Still another benefit in waiting until after the first frost is that germinating winter annuals like common chickweed and henbit will also be controlled. Applications made in September may miss some of these later-germinating winter annuals. To maximize success with any broadleaf herbicide, try to apply on a dry, warm (>550F), sunny day to maximize effect.