Yacon propagules (or caudices) are easily bought these days, and most new yacon growers will quite rightly be expecting to save their own replanting material for future years. Certainly, that's what I confidently planned when I first grew the crop, but in fact I found out that it's quite easy to lose yacon caudices during winter if they are poorly stored.
So, simple enough you'd think, but finding a successful storage method has taken me a few years, and resulted in a few failures along the way.
I've tried storing them in plastic crates of damp compost in a greenhouse (one time frost got in, another year 'sweating' caused rotting).
I've tried storing them in cardboard boxes in an unheated room in the house (some dried out, while some sprouted far too early, and were then difficult to keep alive until planting out time)
Some growers claim success leaving them in the ground, but this can't be totally reliable, and would only work in favourable climates. The climate here is decidedly unfavourable.
Maintaining ideal moisture levels is not so easy, but my experiences have led to this method:-
When lifting crowns in autumn, I remove most of the spindle tubers for eating, but leave a few of the small ones attached. These (I assume) provide the crown with a reserve of moisture. Do not separate the caudices for storage — leave them attached to the crown, where they will be able to draw on moisture from the spindle tubers.
I brush off as much of the attached soil as is practical (if it is wet), and cut off the stumps of the stems as these often seem to be the starting point for rot during storage.
If the crowns have been lifted in wet conditions, I would leave them under cover for a day or two to dry off.
I then place the crowns in lidded buckets (the lids are perforated to avoid condensation) surrounded by a mixture of almost dry spent compost and very coarse sawdust. Any open and slightly damp medium will do, the important point is that it should not be too moist.
I then hang the buckets from rafters to exclude mice.
In March, I start checking the crowns every week, until I notice signs of growth...
I prepare by gently brushing away the storage medium to reveal the caudices, being careful not to harm any shoots ...
Each crown should provide between 5 and 15 propagules. Larger caudices can be further divided as long as each piece has at least one viable bud, but I prefer to leave them whole to make really strong plants.
Pot immediately, and keep in a greenhouse, perhaps potting on again, before planting outside in May.
I've noticed that poorer, smaller plants, often provide more propagation material than larger ones. Based on that, and the fact that I got about 15 propagules from each of my plants, you should be able to work out how bad my crop was last year!