Brassica seeds- question?

How easily do brassicas cross pollinate? I always let my kale go to seed because I like it to self seed and the immature seed pods are yummy. This winter I left a lot of stuff in the garden, several kind of cabbage and brussel sprouts are flowering right next to my kale. I'm wondering what I will get if I let them all go to seed and self seed. Will it mess up my yummy self seeding kale that grows and takes care of itself every year?

That depends on what you consider messed up. If you want your kale to stay just the same, then yes this will mess it up as all of those things easily cross pollinate.  Kale volunteers in my garden as well but those others like cabbage and Brussels sprouts are more difficult to get seeds from in my climate. I have been purposely letting them and any other members of that species that I can nurse through winter flower together and I encouraging crossing.

I like the flavor of the other plants in that family better than Kale but want them to be more winter hardy so I'm just trying to recombine the genetics of that species and then selecting for flavorful flower clusters and stems, young leaves and stalks. I'm calling it broccol-ish. Sounds like in your climate it would be easy to accomplish what I'm trying to do but if you do want your kale to stay pure you will need to remove the other plants.

*I think there are some kales, that are technically a different species so if that is the kind you have it won't be a problem.