白及是一年长一个块茎。若多年生的,茎后的三个为最好,三个以后的加工后粉性低,干瘪、色泽亦差,老药农都弃之不取。采控时间最好是立秋前后。此时白及粉性高,加工收率也高,过早挖收率低,粉性差,干瘪少肉, White and one tuber a year long. If it is perennial, three of the stems are the best, and after three, the powder after processing is low, and the dryness and color are also poor. Acquisition and control time is best before and after the beginning of autumn. At this time, the whiteness and powderiness are high, the processing yield is also high, the early yield is low, the powder is poor, and the meat is dried and the meat is dried.