The sunchoke is the nonfibrous, plump tuber of a North American sunflower (Helianthus tuberosus), whose traditional and obscure name is “Jerusalem artichoke.” It’s pleasantly moist, crunchy, and sweet when raw, and becomes soft and sweet after brief cooking. When cooked for 12–24 hours at a low temperature, around 200ºF/93ºC, sunchoke carbohydrates are largely converted to digestible fructose, and the flesh becomes sweet and translucently brown, like a vegetable aspic.
Salsify (Tragopogon porrifolius), sometimes called “oyster plant” for the supposed flavor resemblance, and black salsify or scorzonera (Scorzonera hispanica) are Mediterranean natives. Their Eurasian relative burdock (Arctium lappa) is most appreciated in Japan as gobo. All three of these elongated taproots become undesirably fibrous with size and age, are rich in phenolic compounds (those in gobo are potent antioxidants), and therefore readily turn grayish-brown—at the surface when cut and peeled, throughout when cooked.