Beta vulgaris maritima
Sea beet. Perennial, growing up to 1.2 m (4 ft) high when it flowers, native to the coasts of Britain and Europe. A parent of Swiss chard, the leaves are similar but with less of a thick mid-stalk and are excellent eating cooked. Likes sun or part shade and a well-drained soil; hardy to -15°C or so, but will resprout if damaged by frost or after harvesting.
Out of stock - for plants, check in July for availability next autumn/winter