HOW long?

Plan X (Where X is an unknown, coz I've lost count)
I couldn't believe it - so I checked.
On Wednesday, this week it will have been in the house three weeks.  When it arrived, in an order from Sainsbury's, it look pretty anhydrous to the extent I'd not have picked it and looked for a fresher bit, or tried next week.  
If you like your ginger fresh keep it on/under moist soil and this is likely to happen.  You can still cut bits off with it in situ.
I spotted the bud from above…
"HUH! I don't remember that."  
Lifted it for a closer look, turned it over and beheld the roots.
I do not recommend it as a "grow your own" crop as a few years ago one summer only yielded one bit the size of a golf-ball but it certainly does not get any fresher.