By Justjo
United Kingdom 
Hi thank you for your swift response, I now have one further Q. When the veg patch is cleared for the winter, will it be ok to treat with weed killer to kill oxalis etc before covering with black plastic sheet. Which weed killer do you suggest and Would the weed killer endanger the raspberry canes 1mtr away? I do not intend replanting anything until the spring.
regards
Justjo
15 Jun, 2016
Answers
and if you are covering it with black plastic they will die off anyway in time. agree about not using the weedkiller.
15 Jun, 2016
Covering with black plastic sheeting for six months isn't long enough to kill the oxalis completely - it'd need to be in place, firmly anchored to exclude all light, air and water, for up to two years I'm afraid.
15 Jun, 2016
yes it is a tenacious little critter. Missed or ignored it was about oxalis !
16 Jun, 2016
I'm not even convinced it won't miraculously revive even after two years either...
16 Jun, 2016
In my experience, the only weedkiller that permanently kills Oxalis is one that would disable you from planting for at least six months to a year, and is used by groundsmen for the surrounding areas of a field. I'm afraid you need to dig it out - they usually have an opaque or whitish, small swollen and bulbous root anywhere between a quarter to half an inch long, and you need to make sure you get those out.
15 Jun, 2016