How long have you waited since you saw roots? It can take a little while. Most people root them directly in water, with toothpicks to prop them up. They miraculously don't rot, though changing the water frequently is a good idea.

Perhaps exposure to sunlight will stimulate sprouting? It's not supposed to be necessary. Warmth is important.

If you want to plant them directly, depth is mostly irrelevant. You can plant them halfway to give exposure to sunlight, or plant them entirely just beneath the soil. Even deeply planted roots will sprout - they perennialize in Houston under mulch.

This post was edited by greentiger87 on Wed, Jun 11, 14 at 14:27