The bottom is often somewhat concave, and there should be a bump, or several, at the top where the leaves will come from.

I could not figure it out either. I planted them every way possible and when the first one appeared I dug them all up and turned them as needed. Al

I have read before that whenever one is really in doubt, it is best to plant them on their side. That way they stand a much better chance than if planted upside down.

Good luck!

chemocurl...aka Sue

Here is a link that might be useful: Google images