[wbmkk]

My plot is pretty much empty now, except for a few sprouts and leeks, but with plenty of weeds.

Would c chemical weedkiller (Roundup) work now, or is it a but too late in the season. I wanted to kill the weeds, then dig over the plot for the winter.

thank you

[New shoot]

It will work, but will be a slower process as the weeds are not growing so actively.  I would leave the really deep rooted weeds 6 weeks after treatment before digging.

If you want to get digging before then, you would be best to get out as much of the weed roots as you can, then treat any regrowth in the spring before planting 

[Salmo]

From my experience Roundup works right through the Winter. As long as there is green leaf it will do the job As has been mentioned it may be slow. You will wait and wait but eventually the leaves yellow. Once the weeds start to yellow you can dig them in, they are clinically dead.

Obviously avoid frosty days and you still have to follow the instructions i.e. the leaves should be dry and it must have 6 hours dry after application. That can be difficult to achieve in the Winter. It seems to work ok if the leaves are a little damp but I would avoid heavy dew.

It will only kill plants with green leaves above the ground. After you have sprayed more weeds may germinate and dormant couch may sprout. If it does then you will need another dose.

A good way to apply Roundup and avoid spray drifting on to your sprouts it to use a dribble bar on a watering can. These are cheap from garden centres. They are a plastic tube about 30 cm long with a series of holes along.