Horseradish Greens aren’t sold. Only home gardeners have access to them.
You can sauté young Horseradish Greens, steam them, boil them or chop finely to add into salad. Some people use the older leaves as well, chopped up and cooked in with other greens.
In the Middle Ages, people commonly ate the leaves of Horseradish plants, in particular the Germans and the Dutch.