Weeding in what we call the big field can on the whole only be undertaken by hand. This means strimming by hand and in extremely hot weather, the weeding machine just can't cope with the old vines. So the rows are weeded twice during the growing season with the last passage taking place in September, although with all the weeds around doesn't look nice and goes against all the text books the vines don't seem to suffer. I think this is due to them not carrying loads of grapes and therefore not being pushed to hard and consequently not being stressed? This is my simple take on the situation but the proof is in the pudding it works!