Spreading a bit of soil over the stems would probably speed up the rooting, but you could also snip short peices off, remove the lower leaves, put them together in little groups of 4-8 cuttings, and stick them into the ground where you want them to grow. Water them in and don't water again till the soil's dry. Most of them will root, and when any of the stems get long enough again, do it all over. This should spread them even faster than just waiting for them to root and spread on their own. You don't need all tip cuttings to do this, either. If the stems are long enough, you can cut each one into several pieces. Just be sure you're sticking the BOTTOM end of the stem into the soil.

Happy propagating,
Skybird