Boiling water: milkweed loves it and undergoes a growth spurt after having been drenched with boiling water; others are unfazed.

Ammonia: it’s a fertilizer.

Bleach: nothing.

Vinegar: nothing

Salt: you have to till in enough to kill an army. Sprinkling a little around the base of a plant does nothing.

Rubbing alcohol: no effect that I’ve noticed.

Cornmeal: what are they smoking???

Newspaper: Bermudagrass and nutgrass will grow right straight through it. They’ll cut their way through several layers of black plastic, too.

Here’s what works: Get some concentrated Round-up. Brew up a pretty strong version by mixing some with a little less water than recommended. Put it in a bottle with a dripper nipple–I use an old Spray-&-Wash bottle that came with a dripper, not a sprayer. Do not use a spray bottle for this.

Drip the Round-up carefully ONLY on the weed’s green leaves. Avoid getting it on the ground. Do not get it on any nearby desirable plants. This will take a few days and possibly two or three applications, but it’s your best shot at killing weeds. Round-up is said to degrade in ultraviolet light, and so if you don’t splash it around you’re not creating a very serious environmental threat.