I've canned turnips, cut up a few greens in with em and they are pretty good, that is, if you like them, and I do. I have pickled plenty of cauliflower but never canned it.
I have canned Broccoli Broth, when I pick broccoli, the ends that are starting to get tough, and any flowers that have bloomed get boiled down and I strain the pulp out, put he liquid in jars and throw it into the pressure cooker. I like cream of broccoli soup and it makes a decent base for it, it can have a little off flavor but if you are careful and use fresh broccoli crowns along with the broth it can come out pretty good. I was raised to waste nothing and old habits are sometimes hard to break.
A lot of people find it a bit odd that a big gruff grandpa takes the time to can his garden produce, but I have been around canning and stocking up for the winter all my life and I am trying to teach my daughters how to do it so I wont have to anymore.