Leaves photosynthesise sunlight to create energy for the roots which, in turn, take up nutrients and moisture form teh soil to maintain their food factory. Take away the leaves and the roots will eventually run out of oomph stored in their own cells. Just pull each leaf. No need to to cut or dig unless the soil is very dry and hard.
Vendée - 20kms from Atlantic coast.
"The price good men (and women) pay for indifference to public affairs is to be ruled by evil men (and women)."
It will gradually weaken them and should eventually kill them, but it might take some time. I believe they have tuberous roots so there'll be a lot if energy stored and they'll be able to keep pushing up new leaves/shoots until it's completely exhausted.
Doncaster, South Yorkshire. Soil type: sandy, well-drained
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Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
Thanks again.