The soil is removed from the underground bulbs of wild lilies and graded in size. The large ones are used for medicinal purposes and the small ones are used for seeds. When processing, peel the bulbs into pieces, boil them in boiling water for 5 to 10 minutes, take them out and spread them out on a mat to dry in the sun. The best ones are those with thick flesh, white color, firm texture and translucence.