The fastest ways to kill weeds and unwanted grass include burning them, pouring boiling water on them, or pulling them out by hand, as these methods work almost instantaneously. For a quick-acting solution that works within a few hours, you can use a commercial-grade herbicide like glyphosate or a DIY vinegar, salt, and dish soap mixture. While effective, be aware that commercial herbicides introduce chemicals into your lawn. The slowest method for killing weeds is to starve them of sunlight and nutrients using mulch or fabric covers.

Landscape fabric and a few inches of gravel should be enough to put under a deck to prevent weeds from flourishing. If you don’t want to invest the time and money on a project like this, you can regularly spray the area underneath your deck to kill weeds.

Vinegar cannot tell the difference between weeds and desired grass types; it kills everything it touches. Only use a vinegar or vinegar-based solution if you are relatively confident that you can navigate around the plants and grasses you want to keep. Also, don’t spray vinegar on a windy day, or it will blow onto other plants.

All herbicides come with risks, but you can control and mitigate risks by discussing your options with your weed service company before application. Some companies use milder or sustainable herbicides more times per season to control weeds rather than one to two herbicide sprayings annually. You can also ask your professional about pet-friendly and kid-friendly services. In most cases, though, you can wait a few days after the application for the herbicides to soak into the ground, at that point they shouldn’t pose a risk to you or your family.