So, it frosted. In some areas, it was a hard frost with temperatures down in the 26 degree F range, and in others, plus/minus 30 degrees. At this point in October, the question is: Is it a good idea to apply a post emergence herbicide to the lawn, considering the recent frost? The answer? It depends.
First, what’s the target? If it’s spotted or prostrate spurge, puncturevine, vervain, purslane, prostrate knotweed, green foxtail, crabgrass, goosegrass, sandbur, mallow, black medic, common chickweed, shepherd’s purse or barnyardgrass, then it has either died on its own once the heat of summer took effect (winter annuals), or in the case of summer annuals, died with the frost. These weeds do not need to be controlled.
However, if the target is a perennial broadleaf weed such as plantain, dandelion, ground ivy or field bindweed, then it may be wise to make an application. The key factor here is the degree of influence that the frost had. If the leaves are soft and water-soaked in appearance, it’s unlikely that the herbicide application would have the desired effect, whereas if the leaves are green, stout and healthy appearing, then weed control is probable.
As with all applications, it’s wise to read and follow all label directions, especially ones related to wind speed, amount of product and water to use and protective clothing to wear.