You can also try adding some nitrogen (urea or ammonium sulfate) to the mix, if you have any on hand.

Water a few days before to encourage the weed to grow. Then apply the chemical.

2-4,d kills plants by using synthetic auxins. Without getting into too much detail, natural auxins are what tell the plant when (and where, e.g. Roots, top growth, etc.) to grow. Basicically, the synthetic auxins tell the weed to start growing everywhere all at once.... roots, shoots, top growth, etc.. all start growing without regulation and --- because 2,4D is LOADED with synthetic auxins, the growth is in overdrive.

At first, the weed might start to grow & spread like crazy, and you start looking at the warranty on the bottle. But the unregulated growth is the demise of the plant. It grows itself to death. You will see the plant twist and grow in odd shapes, as it's using all of its energy to grow. The it runs out of energy and dies.

The trick is to make sure you water a few days before hand so it's already in growth mode, and then water it about 2-3 days later so it will keep growing. It won't work if the plant isn't growing.

Great advice guys, thanks. I didn't really know how it worked, so this is all great advice.

Yeah, it basically burns through all the plant's resources until it dies. Back in the 90s I had a dandelion shoot grow into a perfect curl after spraying with Weed-b-Gon.

There is a reason why weed killers are most effective during the active growing season. That is early spring. Repeat application by spot spraying will guarantee the effectiveness.