These plants will not tolerate a frost but they overcome that by remaining dormant until the weather warms up. Growth is rapid, full size in just a few weeks and they suddenly yellow and die off as the nights draw in during October. I always lift the tubers, clean them and store them dry until the following year. If planted in the ground they can drag themselves down really deep and if the situation does not get waterlogged they can naturalise. One frost on the tuber though and its mashed potatoes.