Sounds sort of silly, but we normally seem to focus on the "Columbian Exchange" as being between the Americas and Europe, but New World foodstuffs spread to the rest of the world too...so when and how did the potato get to China?
More information and answers will be always very welcome also for me (exactly speaking, as a non specialist in this field), but here I post some of my previous answers to similar questions thread:
Put it shortly, the potato seemed to arrive at first in the Far East around 1600, but it had certainly not attract attentions as maizes and sweet potato did at least until the first half of the 18th century. Then, some areas with colder climate began to appreciate the potential of this plant and to cultivate it.