I grow a black satisfy plant in every bed. It grows anywhere. The leaves are a bit thicker than lettuce but are mild and sweet till May when they get thread like fibres along the leaves. My ducks ate them to the ground in spring but the chickens leave them alone. The roots are very deep one foot if you treat it as a biennial. You can leave it in the ground for years and the roots grow larger without getting woody. It has pretty but few yellow flowers.not too many though, you could do better for the bee's to grow carrots. They are very early I see the leaves before I see my tulip leaves and harvest when they are the length of my small finger. Hostas are also tasty but have threads in the leaves. They sprout like a rosette but if you put an upturned flower pot over them they will produce a shoot more like asparagus and you get a substantial harvest before they get too stringy to chew. My favourite perennial green is linden because you can get different harvests the whole year and it is up off the ground and great for bee's.