Control of speedwell in lawns
Please provide advice for controlling speedwell species in lawns. I may have both both annual and perennial types since it has disappeared overwinter in some areas of the lawn; however, in other areas it is thriving under the snow. I have tried broadleaf herbicides: Triplet SF (2,4-D, 2-methyl 4-chloro PP, and Dicamba) with the addition of Quinchlorac as a tank mix but it hasn't helped. I've been looking at pre-emergent herbicides but the label descriptions of speedwell control don't inspire confidence. What are your recommendations.
Hello. As you are finding out, controlling this plant is very difficult. The annual speedwell is not something you would try to control in the spring since it is going to die BUT will set seed for next year. This means a preemergent in the the fall is best. For all varieties try to mow when it is flowering. For the perennial types, university research recommends quinclorac as most effective. It is best not to mow for a few days before application because then the plant will have more leaf surface for the herbicide to do its work. Also, there should be no rain or irrigation after application for 24 hours. The plants should be actively growing (spring or fall). Do not be in a hurry to remove plants that are dying, just because they are wilting or turning brown does not mean the roots have been thoroughly eradicated. If all fails, there is always hand weeding! Good luck.