Killing Nettle Roots?

[taff]

I've dug up a fair few from where we sited the new compost bin thing. In this weather they aren't likely to dry out any time soon.
How long roughly or how do you know when you've drowned them sufficiently to kill them?

[Dane End Dolly]

We did not know that they could be drowned and a year later we are still digging the rotten things out of our beds, still they are coming up less and less

[Two_Sheds]

how do you know when you've drowned them sufficiently to kill them?

Just throw them in a water butt and forget about them for 6 months or so. They will turn into a foul-smelling, but very nutritious, fertiliser

The quickest way to kill them is to leave them on a path to dry out. In the hot sun (it will come) they will turn brown & crispy, like burnt hair