I'm in England, so take this for what it is (
experience from the other side of the world!). Here, even when we've had what was for us hot and dry summers (a couple of months of virtually no rain) the nettles were one of the plants that didn't seem to wilt very much, at least in a shady woodland environment. In our garden they are also one of the few things we don't water and they are never fussed by that.
Incidentally, as the great article posted above mentions, you can also eat the seed - this could be something you could do as well as harvesting the stems for fibre? A herbalist once told me that the seeds act as a stimulant and a friend of theirs ate some and was up all night, very much alert!
Most people here are at best indifferent to nettles because they're everywhere and, of
course, they sting. People find it funny when I say that they are under-valued and that people in other places actually purposefully plant them. Silly because our ancestors used them a lot! Archaeologists think that, because of how incredibly thin some of the nettle fibres they have found are, that much of that work was probably done by children.
