There are several methods of killing weeds without using chemicals, including pulling them, smothering them, and pouring salt, vinegar or boiling water on them. Weeds can be controlled through the use of physical barriers such as lawn edging or retaining walls. In the garden, the number of weeds can be decreased by planting ground cover, flowers and garden crops to compete with the weeds for sunlight, water and nutrients.
Smothering works best on low-growing weeds such as clover and crabgrass. Smothering involves placing several layers of newspaper over the weeds, which blocks sunlight and kills them. Newspaper may also be used under mulch to prevent weed growth.
Pouring boiling water directly on weeds kills them in about two days. Water that has been used to boil pasta or potatoes works great for this purpose.
Rock salt or table salt can be sprinkled on garden paths or along lawn edging to prevent the growth of weeds. Salt must be used with caution, as it usually leaves the ground barren for an extended time period and is capable of eroding concrete surfaces.
Vinegar is an effective weed killer that kills weeds within a few days. This method is especially effective on weeds with long taproots, such as dandelion, dock and plantain.