To kill wild onions, a number of approaches are necessary. The first step is to dig up the entire clump of onions from the ground so no new bulbs emerge from it. After this, it is important to throw the entire clump away without shaking it so no new bulbs reach the ground.
The next step is to use an herbicide that contains glyphosate, such as Roundup, to kill the wild onion. Homeowners can also use boiling water to kill the weed. Using these methods ensures that the weed dies, but it also kills any other vegetation that it gets applied to.