The salsify was a common plant in our lands, but it slowly disappeared since the end of the Middle ages period. It's also called "goat's beard" as the main root is covered with many finer roots. Another name for it is "Oats root", I suppose for the taste. Keep in mind it's biennial, so it'll flower in your garden in 2019 :)
The sea kale grows in the wild on the Black Sea coast, but it's super super tough, like leather. I have no idea how to possibly eat that, except in smoothies and even then I'd be worried for my blender.
Taraxacum officinale is the regular, common dandelion. I've read there are varieties selected, but never really looked into that. We've got tons of dandelions in the orchard, so I wouldn't get them into special cultivation :)
Thanks for sharing the great info @bobydimitrov! I've only eaten salsify a few times from a Dutch farmer who grew it in southern Canada. Quite nice indeed.
As far as I've read the sea kale was covered and blanched to create more tender shoots in early spring. These young shoots were the chosen food, not so much the leaves. Save your blender the trouble!
As for dandelion, you're lucky. We don't really have any on our property. So we're choosing varieties with bigger more tender leaves. We'd be happier if they already grew here though. ;)