@RenaeC - You said, "So really it's best to just mix cinnamon in all the plants". I'm not exactly sure what you mean by that. Are you thinking to mix it in with your potting soil (or whatever you use)? If so, I don't think that would help.
What I've been taught about cinnamon is to dab a little on the cut end of something. Well, I actually have a teeny tiny little paint brush or else use a q-tip. Anyway, it's the same principle as putting a bandaid on a cut. I doubt if this would work for trees unless your cuttings are tiny.
And I could be totally wrong about everything I've just said. Ya never know.
Welcome to NGA!