Glyphosate, the active ingredient in Roundup, is generally considered to be the most effective herbicide for killing weeds permanently. It kills weeds by inhibiting an enzyme that is essential for plant growth. However, glyphosate is not a selective herbicide, so it will kill any plants that it comes into contact with. For this reason, it is important to avoid spraying glyphosate near desirable plants or in areas where you don't want anything to die.

Glyphosate, the active ingredient in Roundup, is a broad-spectrum herbicide that kills most plants. It works by inhibiting an enzyme that is essential for plant growth. Glyphosate-resistant crops have been genetically engineered to tolerate glyphosate so that farmers can spray the herbicide directly on their crops to kill the weeds without damaging the crops. However, these crops are not resistant to all herbicides, and some weeds have developed resistance to glyphosate.