Sea kale is a perennial with dusty, blue-green leaves that grow to 2 feet tall. It is native to northern Europe, the Baltic and Black sea area. It has stalks of small white or cream flowers. Like all the plants in the mustard family, Brassicaceae (formerly called Cruciferae,) each of its flowers has four petals. The corky seeds fall into the sea and float to their new home. It can also spread like a tumbleweed, the dry fruit stalks blowing across rocky screes and shores. There are around 29 other species of Crambe, found in Europe, Africa and Asia.
I first ran across the name of this plant while putting together lists of perennial vegetables. Today at the nursery where I work I admired it as we rearranged the plants. The thick foliage is deep purple and ruffled as it emerges from its pot.
A customer asked me how hardy it is and I found out it can survive winters in USDA zones 5 to 9. The young stalks are eaten in spring, often blanched in the garden like asparagus or endive.
Update on April 19, 2014
I’ve grew sea kale in my garden for the first time last year. I purchased seed for a variety called ‘Lily White’ from Bountiful Gardens and they grew readily when started in flats in an unheated greenhouse on a seedling heat mat. I did nick the corky outer seed coat before planting. I planted the seedlings out in May.
I also grew plants from divisions of roots and crowns planted in a mix of sand and seed starting soil. They grew to be full sized and bloomed the first season.
This spring as they came up I blanched the shoots with a black pot. They are still too astringent to eat raw, in my opinion, but are good steamed. This plant is a beauty!