Harvest once about HALF of the leaves start to fall over and die off (turn yellow) -- HOWEVER I'm not sure if you planted at the being of October or the end. Given good growing conditions it should take about 120 days -- if you planted at the end October then that is about 120 days.... but it could take longer -- and since the leaves have not fallen over, then I would say, it will take more time. If you planted at the beginning of October, then you are taking a lot of days -- and it could be that the growing conditions have not been optimal for the whole time.... and I would still wait for leaves to fall over... but I would start to wonder if perhaps for some reason all the conditions that your plant needs to have met in order to set tubers have not been met (nutrition, soil type/ph, water, sun light, temperatures etc.). Same rule for potatoes, harvest once the leaves started falling over and turning yellow. That is to say: as long as the leaves are a upright and green they are still collecting light and storing energy (making tubers - and making them larger)

- Celeste Archer