Starting begonia tubers – update
Well, here we are 3 weeks on. First, the single large tuber, sporting at least 7 shoots that I can see:
then the 3 smaller ones:
By the looks of it, the top one of the group of 3 is pretty much ready for potting into a properly-drained pot as there are roots appearing above soil level that ought to be covered (when the tubers are potted up they should be covered with a little compost because they apparently root from the top as well as the base).
This is the point at which I usually manage to get things wrong and end up with tubers that simply sulk and refuse to grow any further, so I shall have my fingers firmly crossed from now on!