Crambe maritima

Photos by Mark Dwyer

I first grew sea kale in the late 1990s and was immediately smitten by the glaucous blue, thick, wavy-edged leaves. The foliage was a contributor from early spring as it emerged heavily ruffled from a basal mound with hints of purple and filled out to a prominent blue-green cast. The foliage quickly reached over 30 inches in height on mature specimens with showy white flower coverage in summer. The fact that sea kale is in the cabbage family (Brassicaceae) is not surprising and the foliage is frequently described as “collard-like” in appearance. It’s a shame that this perennial is not used more often for its lengthy and significant ornamental contributions (and edibility). I repeated specimens of sea kale throughout a sunny garden scheme to create a pastel blue “color echo” that really worked well with this durable plant.

Growing natively along coastal seashore areas of mainland Europe and the British Isles, this plant is also considered a halophyte which indicates its high salt tolerance. Since the turn of the 18th century, sea kale has been a popular vegetable in some parts of Europe (particularly England and France) with leaves, stems, flowers and roots entirely edible. Sea kale is high in vitamin C and contains calcium and other nutrients. Early shoots are commonly cut in spring, blanched and steamed. Young leaves and flower buds can also be eaten raw. Thomas Jefferson also grew sea kale at Monticello in the 1820s. The profuse, small, four-petaled white flowers are about ½ inch wide and are slightly fragrant. Held in dense panicles above the foliage, the flowering show is not insignificant and is “baby’s breath-like” in appearance.

Best grown in rich, sandy to gravelly soils with medium moisture, sea kale also prefers good drainage and ideally a neutral to alkaline pH. Full sun is preferred although very light shade is also acceptable. I had a dozen specimens of Crambe maritima thrive for over 20 years in the same locations. Propagate sea kale by seed or root cuttings. Division is best accomplished in spring. Slugs and cabbage moth caterpillars can occasionally make an appearance, although this really is a very low maintenance perennial.