Salsify is a vegetable with an air of mystery. In fact, it's two vegetables: white salsify (Tragopogon porrifolius), a pale, crooked root covered in wispy filaments that's native to southern Europe, and black salsify (Scorzonera hispanica), a longer, straighter, and dark brown tuber that grows as far east as Siberia. Both have a delicate, vaguely mineral flavor reminiscent of artichoke hearts' or, some say, oysters'. In fact, white salsify is often known as oyster plant. That's the type called for in Catalan home cook Maria Pol's recipe for Chicken And Salsify Casserole, but we recommend using whichever variety you can lay your hands on, as salsify is something of a rarity in U.S. markets. It hasn't always been so. Thomas Jefferson grew salsify in his garden, and it was on the menu at New York's legendary Delmonico's restaurant in the 1890s. The ingredient also appears in multiple preparations—including a simple saute—in the original Joy of Cooking (1931). But people stopped cultivating salsify on a wide scale in this country in the mid-20th century, and no one knows why. Truth be told, the vegetable is fussy when compared with sturdier roots; it breaks if pulled from the ground too roughly, and it spoils rapidly. Once salsify is peeled and cut, it must be stored in acidulated water (water with lemon juice added) to prevent discoloration. But a little vigilance invariably pays off. No other root can duplicate salsify's charms: its mildly sweet, nutty flavor, its tenderness, and the dimension it adds to a rich stock or a buttery glaze are incomparable. Its obscurity only enhances its mystique.