are they still completely dormant... if so.. i might put box/bag and all in the coldest part of the basement.. and ignore them as long as possible .... hoping to hold dormancy as long as possible ...

when is your target for frost free enough to go outside????

in my MI ... they could not go outside until mid to late may.. and it simply would be a nightmare to deal with until then ... how does your part NY compare ...??

go figure on a dahlia forum.. lol .. who knew ...

ken

And when I do pot up in April, do I pot with intention to transplant or sink the pots? And what medium?

Just as easy to pot them up now in whatever size containers the tuber will fit in and either store in cool dark conditions until sometime next month or grow on now and plant out when your weather permits. This is SOP for dahlia growers in my area, as our soils do not warm up sufficiently to promote much growth until well into May. Regular old potting soil will work fine for this short a period.

There are cautions about storing bulbs in a refrigerator that you keep fruits or some types veggies in as they can emit ethylene gas that will prevent flowering. Not sure if that applies to tubers like dahlias as well but l'd investigate before doing so.

Start over.

They will not be able to be planted until at least the middle of May. That's 3 months where they will have to be grown in heated space. Do you have that much south facing window sill or light setups?

IF the answer to the previous question is no, STOP, you cannot start dahlias early.

If you do have appropriate places to keep them, potting a lot of dahlias requires a lot of potting medium. Whatever it is, you will need a lot of it. I usually use old, used potting soil for things like this because it is cheap. Larger pots will need more medium. Depending on your definition of a lot, this can mean bags and bags of whatever.

This is what I am doing. I have (maybe riskily) lifted mine which are currently sitting on the floor of my greenhouse in boxes of used (from last years tomato starts) potting mix. I have separated the (huge) tubers into reasonable chunks (ie, with a decent growth 'eye') and will be bringing them into my kitchen and prop room to force them into early growth...which I will immediately remove from the tuber and insert into rooting hormone and a loam and perlite based soil mix.

Using bought-in tubers, much depends on size and vigour...and some shrivelled tuber in a plastic bag is never going to yield much cutting material...but a healthy, fat tuber can be encouraged into producing new shoots around 3 times, from each eye bud...because I also want a lot.

In truth, the potting mix is largely irrelevant, at this stage. It is just a means of anchorage and moisture holding. Only once green leafy growth is really underway (when the season heats up) is it essential to keep up with feeding.

If you are not terribly interested in increasing production via cuttings, it is better to hold the tubers in semi-dormancy for a bit longer. As they are short day plants, nothing will induce earlier flowering, anyway...so an early start means keeping growing tender plants in frost-free conditions (and hogging all the room in my greenhouse and cold frame).

I have seen tubers literally sitting on top of sandy soil while the shoots are harvested for cutting...but space is usually my main determinant, rather than type of mix.

Thank you, thank you. I think I have received the answers I need to apply the timing of Gallica to the method of Campanula, heeding the warning about vegetables in the same refrigerator supplied by gardengal. It would seem all bases are now covered.... although I won't be surprised to read some new information addressing questions not yet imagined.

Oh, I thought of one! If you were to stoop to supplementing your own tubers with those now put out at HD, would you buy them NOW and store yourself, or pick over what's left next month and into April?

Since HD probably has them inside, in too warm conditions, you should get them ASAP, before they start growing.