We definitely landed in Huangya at the height of crabapple season: all over the place there were people cutting them into thin slices with secateurs and laying them out in the sun (eg, see here).

The accepted wisdom amongst the trekkers (which may of course be completely incorrect) was that crabapples can't be eaten, so maybe they're going to be used to make a dye or something? OK, maybe "accepted wisdom" is a little strong for such vague hypothesising, but there you go. If anyone knows better, please tell me! :-)