Much better to underwater than overwater the tubers when you are getting them going. They have food & moisture stored. I start them in barely moist potting mix (dryer than I use to start seed) and don't water them until I am sure they have begun to develop a root system.
Because I start them in zip locks - I can just barely cover them, and then add more soil as the sprouts grow. It makes it easy to see the roots as they develop. It also makes it easy to check to see if the tuber is still healthy. It seems there are always a few that I identify as healthy, that then rot as I try to get them going.
Some tubers are fast starters and others that I consider giving up on, but then after a month actually do quite well. It does seem that usually when one of a variety sprouts, then the others do too with in a few days - but not always. At this point most of mine have eyed up, but there are maybe 20% that I am waiting on...........I check them every couple of days. I get a little obsessive about them
