The last roots I harvest in the autumn are perennial vegetables for eating in the winter. I usually do this as late as possible and some years harvestng involves breaking through the ice with a pick axe! With daytime temperatures of -7C forecast for next week, this may be the last chance! Yesterday was the annual horserdish (pepperrot) harvest….the big roots are for forcing young shoots as a vegetable (usually blanched) and the younger roots for grated horseradish! An annual dig also serves to limit the spread of horseradish which can be a problem in some gardens!
See my webinar from last winter on winter vegetables here: https://www.youtube.com/watch?v=sf1ucsGrU2U