@UnicornEmily Sweet, I just harvested my broccol-ish seeds as well. Some, probably a lot had already shattered or been eaten by LBBs, little blue birds. But I have more than enough. I saved:
Kale-like but better flavor - 2 plants
Cabbage like with purple leaves red veins, most delicious of all - 1 plant
All mix - estimated 30 plants
I did not save anywhere near all of them, most are just scattered to see how far they have gotten on the path to becoming feral, the ultimate goal.
Although I let a lot just get lost as they would, I saved plenty of seeds to add into the seed swap package at end of season.
Here, assuming it works is a little video I made of some odd broccil-ish that showed up.
It also applies a bit to this topic. How to prepare soil - #13 by markwkidd