Some backbulbs will grow a new lead and roots, others will not. People place them base down into damp sand or fine Cymbidium potting material to see what happens. Some growers throw them away unless they are dealing with a valuable plant. Divisions should be a minimum of the newest lead and 4 growths back from that lead. Optimum time for repotting, division is spring. I use a mixture of treated pine bark and coconut chunks plus a small amount of Diatomite. There are a zillion Cymbidium potting mixture recipes, perhaps you can buy some ready made up potting mixture in CA. I clean leaves with Eco oil and water which is a concoction of Canola oil, plus eucalyptus oil. Something similar is certainly available in the USA.

Rhizome is root mass below the surface. What you did was to cut a shoot that was just starting and will now die. In order to get a viable start of a clumping bamboo, you will have to get a decent size chunk of rhizome and, preferably, at least one fully developed culm. Unfortunately, clumpers have dense, woody rhizome systems. The last time I divided one, it took 1/2 hour with me pounding on the foot rest of a sharp, steel spade with a sledge to force it through the roots like a chisel. Some clumpers are less difficult...but you get the idea. You're not just going to be able to take a small piece and call it good. Unless you can get viable root mass, you're not going to get anywhere.

I have had best results early in the spring, when you can see them coming up, but they are pretty small. Fall works too but it takes more watering and it is risky with winter coming on. What sort? Maiden hair has been the toughest for me to get divided successfully.

I have always divided in the spring as soon as the sprouts appear big enough to be seen properly. Interesting info keesha! I am going to have to look closer at the hosta this year and see how they look. Maybe I will have to give it a try. I never really thought about whether they were nicely rounded mounds.....I am kind of a 'plant it and be grateful it grows' kind of gardener,:) so unless something is extremely unruly or floppy, I don't really think about it, although I am always impressed when I do see a beautifully shaped plant in the garden. gg