Seriously eyeball those begonia tubers if you bought them at the end of the season. If they were in baggies, maybe with a covering of sawdust or similar - they could be past their use-by date already. If you bought them in a punnet, and they still have remnant stalks, plant them on into small pots - one size larger. Put them out of the way of any frosts greater than 1 degree. Around Easter (I'm guessing) start checking for the little pinkish buds as they emerge. When the leaves are early-out - pot them on into a fresh and richer mix and start feeding them weakly-weekly. Protect against late frosts. Pot on as they start gaining size - or plant out into the garden once the frosts have finished. If you are zone 9a or higher you can leave them in the garden without lifting them. Just mark them so the tubers don't get stabbed while you're weeding. And feed them with a side dressing of new compost plus fertiliser each spring. If you leave them dry over winter they are slow to start up. First up are the tubers over-wintered in their original potting mix; then the inground tubers, with the cleaned and kept dry tubers last. (That's how I find it in this zone - 9a.) They often start flowering in early summer more than spring, but could be earlier in a higher zone than mine.

Growers have been experimenting with this. Rick Tasco of Superstition in Cathey's Valley, near Mariposa, plants his slightly beneath the soil, and so do a number of other growers across the country, and they all report good results and fewer losses. It is now understood that rot comes from a bacteria that gets into the rhizome through wounds or cuts, not from burying the rhizome too deeply. I am going to try it next year.

Great! Thanks for the encouragement. I held off doing it, waiting for my re-bloomer (white, think it may be Immortality) to finish. Good to know it's still possible to divide the crowded beds.

I'd not be inclined to do it now......January is just not the most ideal time for this type of activity nor is it best suited to the plant. Ideally, midsummer to early fall is the recommended time for this process, as bearded iris enter a period of semi-dormancy about 6-8 week after blooming that allows division and transplanting with minimal stress or transplant shock. You can also do this in early spring, but will most likely be sacrificing most, if not all, of this season's blooms.