I started the same species in wet papertowel and ziplock bag on Jan. 16th and on Jan 30th three seeds began to sprout, in a couple of days I hope they all will start and i'll pot them.
Here the temperature is still very low -4°.
Giorgio

Girgio - did you start yours indoors or out? I assume they are indoors? I winter sowed mine, which is a new method of sowing seeds - even with those temps of yours. Is that celcius or fahrenheit?

I think it will take a while to develop the tuber.

Susan