You can graft Marijuana and you can "air layer" also. There are different methods for different plants and trees, cloning doesn't work on everything.
Air layering is cool, I have done it in my garden, but not with my girls. In theory, you could have several rooted clones on one plant, just snip them off and use....meaning your count wouldn't go up until you cut the babies off the mom. I have talked with someone who was successful at doing this with cannabis, and it really isn't that hard...except the size stems you would want to root would be pretty small to deal with.
Basically, you make a slit in a stem, I use a piece of toothpick to keep the "wound" open. Apply rooting gel, wrap with damp moss, and then a dark baggie type material like a piece of garbage bag, a tie twist can hold everything tight in place at the bottom, you can even use electrical tape.... but a twist tie is best to seal the top as you want to be able to add just a little water every few days until your roots show up. When you have enough roots, clip it off the stem and plant.
Do a search on "Air Layering" and you will find methods and pics.
Fun stuff, I am excited to try grafting some strains on one mom plant....I know how to graft, just never thought of it....thanks for sharing Stelthy