Asparagus, Sea Kale, a cross between cabbage and asparagus, and "Good King Henry" are all great and delicious options and all grow year after year with very little work needed. Asparagus can only be harvested for about eight weeks, let the rest of the spears grow and they can then go back into the ground to build up for the following year's crop. Kale is a hardy, flavoursome plant and should ideally be sown in spring, planted out in June and ready for cropping in the winter.