For cultivation without casing soil from September to March. Sow on well worked soil. Thin out upon emergence. Harvest roots in late August. Allow the roots to die off for a few days on the soil. Cut the foliage of the root 2 cm above the head. As of late September to early February stand the roots in a box or bucket. Keep in complete darkness, otherwise they become green. Forcing duration at approx. 16ºC is 4 to 5 weeks.