Q.Planted lily bulb 5 weeks ago, lily is now 4″ above soil in my pot. how tall before I move to a larger pot?
How big the lily need to grow before I move it to its own pot?
Generally when you are growing potted lily bulbs, you start the bulb in the pot that they will remain in for the duration of their growing and blooming period.
They may even be able to stay in that first growing pot for a 2nd season. After the 2nd year, they will likely need to be divided.
It's unclear what size pot you have used to start your lily, so I'm hesitant to give any advice on moving your plant at this time.