Why do the leaves crinkle?

There maybe mostly 2 reasons. One is because the plant has the genes of C.Sparrow or C.Heng or Ranchang, just because the crinkled leaf is a characteristic of these types . But  now, the clivia which has crinkled leaves is commonly regarded as a low-grade-hybrid, at least , the plant  will be judged as a plant without merited quality. The other is because fertilizing improperly. If you fertilize the plant transnormally , such as adding too much of bottom-manure or border-manure in the pot , the overfull quantity of the fertilizer will do harm to the plant . Therefore, the direct result is that the leaves will crinkle . The resolvent of avoiding the crinkle is to exchange the planting media or stop fertilization until the new planar leaves come out.