Why does my sweet potato have stunted growth with wide, flattened stems and dense leaves?

Question

My sweet potato plant has a severely widened and flattened stem and grows like a band, with dense leaves and stunted growth. What is wrong with it?

Answer 1

Your sweet potato is very special. It has a disorder of unknown cause called fasciation.

From Sweetpotato: Major Pests, Diseases, and Nutritional Disorders (1997) by T. Ames, N.E.J.M. Smit, A.R. Braun, J.N. O’Sullivan, and L.G. Skoglund, page 112:

Fasciation

Cause unknown

Symptoms. Vines become very broad and flattened—fasciated. This symptom becomes more pronounced toward the shoot tip.

Biology. Plants have been known to exhibit spontaneous remission of symptoms. It has been suggested that this is a physiological disorder or that it is caused by a bacterium of the Rhodococcus genus.

Distribution and importance. Fasciation is found throughout the world wherever sweetpotato is grown. It is not known whether yields are affected.

Control. No control is known.

Also see this article on fasciation from the Purdue University horticultural extension. Apparently, the cockscomb form of Celosia, a common bedding plant, is an example of fasciation.

Edit:

I guess your sweet potato is not so special after all. According to A Monographic Study of Sweet-Potato Diseases and Their Control (1929) by L. L. Harter and J. L. Weimer,

Fasciation in sweet potatoes is so general that it is sometimes difficult to find a plant in which it is not present in one form or another.