Responses
Wow you are down to the details huh~~ I think they meant to grow plums and dry it = growing dry plums.... it think.
maybe it's something similar to cooker / cooking apples; a special kind of apple which doesn't really taste all that good except you 'cook' them (then they're great!) - me thinks there might be a special kind of plum which is exceptionally suitable for being dried?
One thing I wondered about. How do you grow dried plum? http://www.mangago.me/read-manga/yozora_no_sumikko_de/bt/190999/Vol1_Ch10/31/