What kills weeds down to the root overnight?

Most reliable lawn-safe herbicides do not truly work “overnight,” but some fast-acting products begin showing visible results within 24–48 hours. Non-selective herbicides can burn down weeds quickly, but they will also kill any grass they touch, making them a bad choice for use in the lawn. Selective, professional-grade broadleaf herbicides work systemically, moving from the leaves into the root system to provide deeper, longer-lasting control. While leaves may start curling or discoloring within a day or two, complete root kill usually takes several days to a couple of weeks. Patience and proper application are key if you want a weed-free yard without injuring your turf.