What is salsify? Let us refer to the Horticultural Register and Gardener's Magazine 
Left: the only attractive specimen obtained. Right: what most of them looked like. It isn't the salsify's fault. My carrots are also pretty homely.
Salsify is one of the many root vegetables that have fallen out of favor with the advent of mass produce transport, along with Jerusalem artichokes, rutabagas, and turnips. It was very popular in the 1800's, mainly as a fish and oyster substitute. I suspect its popularity was also due to its color. Victorians were huge fans of any white- or cream-colored food, to the point of engineering ordinarily colorful vegetables to be pale and anemic looking.
I have wondered for a long time, however, how well this hideous vegetable actually works as a substitute for fish. And today, my dream has come true.
Mock White Fish (Vegetarian Dish.)
Mrs. Beeton's Everyday Cookery (1861)
Ingredients. --Salsify, milk, butter, flour, lemon-juice, breadcrumbs, salt and pepper.
Method.--Scrape the salsify, cut the roots into 1-inch lengths, cover them with lemon-juice, or white vinegar, and water, and let them remain 1 hour. Drain well, barely cover with boiling salted water, cook gently until tender, then strain and preserve the liquor. Take equal parts of liquor and milk; to 1 pint allow 2 oz. of butter and 1 1/2 ozs. of flour. Heat the butter, add the flour, stir and cook for a few minutes without browning, and put in the mixed liquor and milk. Stir until boiling, season to taste, and add a little lemon-juice. Place the salsify in coquilles, cover with sauce, sprinkle thickly with breadcrumbs, and add 2 or 3 small pieces of butter. Bake until the surface is nicely browned, then serve.
Time.--To cook the salsify, from 25 to 30 minutes. Average cost, 2d. to 3d. each. Allow 1 to each person.
Verdict: Danged if when I was peeling and grating, it didn't smell vaguely of fish. Not... not food fish, but more like that smell when you walk past the fish department at the grocery store. Sort of like raw fish and a little like cleaning solution. Most salsify recipes tell you to drop the pieces into water while you are working, and this is a good idea. On exposure to air, they start turning black. They also leak white milky sap onto your hands, which make you smell slightly like a fish counter.
But does it taste like fish? Yes. It actually does. In a mushy, squishy way, similar to cod. The lemon juice in particular makes it taste very close. I should mention that cod is my least favorite fish. I ate two pieces of mine, Husband ate most of his, and 2-year-old ate the rest of mine, cramming pieces in her cheeks like a hamster, chanting "Salsa-feeeeeee! Salsa...FEEEEEEEEE!", and ignoring her spaghetti. I suspect she liked the mushiness and the sound of the word "salsify."
This would be a good dish to make if you had time to spend, space in your garden, and a serious and worrying grudge against a vegetarian frenemy who hated fish.