I have been setting aside some turmeric and ginger rhizomes for growing next year. My understanding is the best ones to use are those with good growth nodules. In the photo below you can see clearly the nodules, they are the raised white lumps on the top and side of the rhizome.
Both of those nodules should shoot up foliage and eventually more rhizome should form behind them.
Well that’s the theory anyway. My hope is that this piece doesn’t rot before it gets warm enough to test the theory. I plan to start this one in water as I’m quite anxious to see the process first hand. The others I will start in situ which is what I’ve had success with in the past.