Common Salsify - Trapogon porrifolius - Oyster plant or purple goat's beard
Common salsify, or oyster plant, is a perennial or biennial plant belonging to the sunflower family, which grows to more than 4 feet high. It has long grass-like leaves which emerge from a thick greyish-white tap root. The flowering stalks bear heads of up to 90 purple florets. It is originated around the Mediterranean but has since naturalised as a weed in SE England and the USA. It is thought to have been cultivated in gardens since the 16th century.
The leaves of salsify are edible and may be added to salads, but the main reason for cultivation is for the nutritious root which, when cooked, is said to taste like oyster. The roots are harvested and peeled before cooking; they quickly discolour if not dropped into water with a little lemon juice. They make a fine addition to stews, or may be mashed and made into patties, or thinly sliced and fried until crisp.
According to Culpepper: This, however, may be eaten in great quantities, and so will be useful in chronic complaints. The roots are particularly specific in obstructions of the gall and the jaundice; the best way to use them is stewed like chardoons'.
Spanish salsify - Scolymus hispanicus - yellow goat's beard or golden thistle
Spanish salsify grows under similar conditions to common salsify, reaches 1 - 2 feet high and bears stalks with single yellow flowers which open at day-break and close at noon (hence the country names noon-flower and Jack-go-to-bed-at-noon). The seed heads resemble dandelion clocks. The tap roots are edible and have a milder flavour than common salsify and were once used to cure heartburn and stimulate the appetite.
Black salsify - Scorzonera hispanica - is a perennial plant which grows in central Europe. It has a black skinned tap-root and broad, spiny, deeply veined leaves which are edible in salads. The flowers are yellow and up to 2 inches across.
According to liveforever: In Danish, Salsify root is referred to as "skorzonerrod" (Scorzonera root) and more commonly known as "fattigmandsasparges" (Poor Man's Asparagus).
gn0sis says: A few more names: salsify is mustajuuri or "black root" in Finnish, because it discolors when cut, and "gobo" in Japanese.