If you have trouble with it staying put, superglue gel is a great tool. A few dabs on the rhizome, hold it in place on the wood or rock for 10 sec or so and it should stick. It even cures under water. I used to use it all the time for sticking coral frags to liverock, and it works well for plants to wood as well. Just brush off the spot where you want to stick it first to get off any algae or detritus that may have gathered.