Sium sisarum (Skirret, Crummock) is a perennial plant of the family Apiaceae sometimes grown as a root vegetable. It has a cluster of sweet, bright white roots which are similar to sweet potatoes, but longer (15-20 cm). Skirrets may be boiled, stewed, or roasted. The woody core is inedible, and should be removed before cooking because it is difficult to remove after.The skirret is of Chinese origin, but may have arrived in Europe in early times: it is presumed to be the siser mentioned by Pliny the Elder as a favourite of the Emperor Tiberius, and was also grown by the Picts.The plant grows about 1 m high and is very resistant to cold, as well as pests and diseases. It is usually grown from seeds, but may also be started from root divisions.