Thanks so much for your response. I was worried about the number of tomato plants I have in each cup but seeing your blog helped me figure out what/when to do the transplanting. I got 4" used containers from the local nursery, cleaned them out & will start transplanting the largest plants tomorrow! Thanks for the advice & the up close visuals & instructions!

It's probably a sucker, not a seedling, so it will be attached to the mother plant. It's chances of success will be highly influenced by how many feeder roots are attached to it. If you dig it up, put the pot in a saucer of water in the shade for a couple of weeks. Once it starts growing, it has roots.

Boca Joe I respectfully disagree...as soon as there are a few leaves, it is safe to bring them outside even close to freezing temps, but they won't grow as quickly as indoors with warmth. I will agree that steady cold rain for more than a full day might be risky. I've had mine outside for 2 weeks already, and they've already experienced 33-35F several times without any problems, sunburn is the bigger threat, they should be gradually introduced to sunshine. I have about 30 clumps of various species, they are all doing well.

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.