It’s rather obvious, even the most amateur gardener, that Crambe are cabbage family relatives. Snap off a crispy leaf, and it smells like a turnip or a radish, and a closer look at its flowers and one can see the four petals which all members of the cabbage family, share ( cross shaped = Cruicifer), be they radish, turnip, broccoli, Bok Choi or Crambe. One species of Crambe ( cramm-bee) is grown as a spring vegetable in England, Crambe maritima, but both are uncommon in the United States.
Native to the Caucasus, the plant can be a little fussy in some gardens, preferring deep loam, moist but not wet soil conditions, and a little space. A common complaint from some gardeners who grow the plant is that their plant’s rarely bloom, and out of my six plants, only one is blooming this year. All plants seem healthy and robust, my only guess is age, and perhaps sunshine. If plants are crowded out by nearby perennials, they often lag behind a few years, or refuse to bloom. Try and leave space between Crambe leaves, and neighboring plants and see if that helps.
I like sea kale, too. I see it's being used more regularly here in borders. I didn't know about not crowding the leaves for a good flowering, so thanks for the tip.