Good question. The longer you can keep them going even as the days get short, the better. Any tuber they form, though will be tiny and unformed. I think the professional growers plant small seedlings in the ground and keep them there for a year or two, if they are undisturbed and left to grow there should be more of a tuber to harvest and sell.

Thanks Woebegonia
They are in pots will try keeping them under lights this winter and see what happens.

Do you think it would do an good to cut off all the buds and blossoms during the rest of the season?

I don't think that would have any effect, it is daylength (less than 12 hrs. a day) which 'tells' the plant it should start thinking about dormancy and growing a tuber. For the male flowers, pollen production is cheap and costs the plant little in terms of energy; the female flowers actually slow growth when fertilized, but I dont think that has any effect on tuber production.

I read that tuber formation is caused by 2 factors: short days and temps below 62F(not sure day or night?).

so i made an experiment with my non-stops.
i got them as 4" plugs blooming in may. grew them in pots, they did not start flowering well until temps dropped to mid 60F at nite, then they finally grew well for 2 months.
i kept them outside until the nights were in low 40s - till nov. oct was unseasonably warm here.
the one that declined earliest - by oct - had no tuber to speak of - about the size of a dime, i chucked it.
when i took them in beg of nov, i watered very little. they were in north window, good light.
then i stopped watering in dec - put them in cool area on low shelf, about 60F-62F with med light. they still had decent foliage on them.
now 2 mo later i finally dug up the tubers from the bone dry pots to check on progress. they are nice and plump, no rot.
the ones in larger pots produced decent tubers for 1yr 4" nursery plugs: about 1.5" wide and 1" thick. 2 are showing tiny red buds, pin size.
the ones in 5" smaller pots have smaller tubers - dollar coin size and 3/4" deep.
i cleaned them up, and put back in just barely moistened medium, top of the tubers uncovered. almost dry, but not quite.
now i'll wait to see if buds will start showing on others.
i am afraid to give them more moisture yet.
RT, what's happening with yours?

I always get really good tubers from young plants depending on when they are started. The ones I let naturally go dormant in zone 6 die down by early mid October bare

Y form tuners the size of a peanut. I found that if I took them inside and put them under a 4' shoplight with 12 hours of light at the beginning of october, fertilize and let them slowly dry by the end of nov I get good sized tuners. I grow the, in 5 inch tall quart pots and can fit about 60 under a shoplight.

I don't get tuners for seeds planted after around march 15.

mine were store bought starts - so it's cuttings, not seeds. and i do take them indoors when temps go down to mid 40s at night and water them just a bit to keep them going for as long as possible. then in dec i stop watering. it takes them a month to decline. i keep them in soil - so as not to dry them out and then in april clean them up and repot/restart.

i read that it helps to remove flowers and growing tips when temps drop below 62F - so they can concentrate on fattening tubers. then 2 more months of growth should do the trick.