Weed killer how long does it take to work?

[Chippychop]

I'm using round up ultra for nettles. I sprayed on Thursday lunchtime but there are no signs of them dying yet. Should I have strimmed them first?

It makes sense (although I had to work it out myself) that the taller the weed is the longer it takes for the weed killer to work its way down to the roots. On small path weeds it should take about a week but you should see signs after about 24 hours.
So if you can bear it then yes I would strim first. And don't forget long gloves and don't do it in shorts

Thanks! Dh out there now. And yes it makes sense now Doh!