First of all, 'do not panic'. These tubers have to be brought out of dormancy at their own pace, and they will grow fast enough when they are ready.

Keep the compost just moist and wait. Just one point. Have you got the tuber set the right way up. They typically have a smooth round bottom, the top having a pronounced depression where the bud should be. The roots will grow from the top.

3-4 weeks is not very long and you may have to wait quite a while.

Moriati

Yes, I think I placed the right way.
But it don't have a depression. There is somehting which look like a peduncle. I supposed that this is the top?

greetings
Peter

Today I noticed that it sprouted. Great !!!
But ... unfortunately I noticed too, that I placed the tuber up-side-down.
What shall I do?

thanks
peter

i know my elephant ear plants need to be placed side ways or upright , i would dig it up and place it right side up , that is if it hasnt started to show through the earth yet, if it has leave it alone