Leave them as they are. You should never divide tubers as in this case you do not end up with two good tubers. you end up with two inferior tubers.

If two stems eventually develop (which does not always happen.. due to apical dominance of the primary bud) you can at that time (when the stem is 3-5 inches tall) remove soil soil above the tuber around the stem. Grab the stem as close to the tuber as at all possible (with thumb and forefinger) and gently rock it back and forth. It will break off by tuber level including a few roots. You can then root the "cutting" after 30 minutes (allow to callus). Let the wound on the tuber stay open for a day or two before covering again.

This is a much better way of propagating your tubers.

Good luck

(I am growing 21 tubers this year.. it is a very addictive plant)

Thank you, this sounds like good advice.

Hi do you root your cuttings in a propagator or on an open bench in a shaded warm postion. Do you feel some bottom hear speeds things up early in the season?

I have tried some in a closed polythene bag to help keep in moisture but wonder which method is most successful?

I usually root mine indoors under fluorescent light with 70F bottom heat.

Thanks for the advice, I have a few in an open top propagator so hopefully they should root.