My dad grows burdock as well as Japanese mountain potatoes (Dioscorea japonica). What he does, when harvesting, is to dig a knee-deep trench alongside the row, then ply the roots out into the trench.
A side story: Years ago, when he started growing the mountain potatoes, someone in Japan sent him the "secret formula" -- he asked for my help in getting the "right stuff" -- they turned out to be things like rice bran, soybean meal, etc. He was SO happy when I told him he can get all he needed from a local feed store, and inexpensively too. Until then, he used to sprinkle chemical granules and powders. After his potato harvest turned out so well, he was totally convinced and he's been gardening organically ever since.