Also known as oyster plant, those roots are somewhat similar to a skinny parsnip in that they can be left in the garden over the winter, if well-mulched. They are said to taste best after a few freezes, or even a whole season of them! My dad tells me his folks grew salsify -- and preferred to leave it in the ground until spring -- even though the rocky clay soil here in Pennsylvania doesn't produce very straight roots.
You can also harvest the flower stalks in the spring of that second year, before they get woody, and cook them as you would asparagus. Some people even eat the unopened flower buds, which I would consider a dreadful waste!
Salsify's official name is Tragopodon porrifolius, placing it in the same family as the western goatsbeard. Its roots grow best in light, sandy, and stone-free soil, which isn't too rich, as excess nitrogen may also cause forking. In suitable ground where the plant gets plenty of sun, those roots can reach a foot in depth and the plant 3 feet in height. The flowers sometimes measure 4 inches across, but close promptly at mid-day, which explains the nickname often applied to members of the Tragopogon family -- John Go to Bed at Noon.
Tragopogon comes from the Greek tragos ("goat") and pogon (‘beard"), while porrifolius means "with leaves like a leek." Salsify derives from the Latin sol ("sun") and sequens ("following"), in reference to how those flowers are supposed to turn their heads to follow the sun.
You can sow the seeds a couple weeks before your last frost, as they will probably take that long to germinate. Soak them overnight first, and plant them about 1/2 to 1 inch deep and 4 inches apart.
The leek-like seedlings will look very much like grass, so be careful that you don't yank them accidentally. After a few frosts in the fall, you can pull, pare, and prepare the roots as you would parsnips. Their flavor is apparently hard to describe, though it combines elements of oyster, asparagus, and artichoke!
Be warned that the paring is a sticky process and the denuded roots will brown quickly. If you are going to brown them in butter anyway, that probably won't matter!
It's best to pull only as many of the roots as you plan to use right away, since they don't store well in the refrigerator. You can leave the others in the ground until you need them, or stash them in a bucket of sawdust in a cold room or root cellar.
There is also a perennial type of oyster plant with darker roots and yellow flowers. Called Scorzonera hispanica or black salsify, its name means "Spanish snake." Although that sounds ominous, it is also supposed to be quite tasty.
Oyster plant's large dandelion-like seed heads look as if they have the capacity for sowing little salsifies far and wide. So you should probably snip off the spent flowers before they go to seed if you don't want plenty of new plants.
Of course, after you've tried oyster plant stew, you may decide that all those goatsbeard "kids" are a good thing!
Photos: The thumbnail and salsify plants photos are Dave's Garden images by knipholia. The salsify roots photo is by Dinkum and the salsify seedhead photo by Javier Martin, both courtesy of Wikimedia Commons.