What’s wrong with my ginger?

A while back I planted an offcut from some shop-bought ginger root in our back yard. It due course leaves grew up to 50cm or so, and then a week or two back they turned yellow and appeared to die off. Yesterday I dug the roots up, hoping to see a nice large thing I could eat.

To my surprise, what I found was small and rather orange, which seems incorrect for healthy ginger. After googling a bit I’m at a loss for a description of what’s gone wrong, but I get the impression it’s something like fuzarium rhizome rot. I’ll have to keep buying ginger for the moment, at least until I can figure out what to do in order to resolve this problem.

Here’s a photo showing my ginger and normal ginger. Pretty obviously bad!