does it perhaps freeze in your pourch?

No, but it does get close to it. I read on another post that you can leave them in the pot in an unheated garage to overwinter. Perhaps it was just too cold. I guess I learned my lesson.

First year plants don't make tubers right away. I bought a gorgeous one a few years ago already blooming. I knew from the leaves it was tuberous because I do grow my own. When the leaves dropped off (I had taken it into the house to enjoy it a little longer) I dug around and couldnÂt find any tubers! Not so much as a pea sized lump. I asked on here and was told it takes a while for the tubers to form. To keep the whole pot undisturbed, let it dry out, store it in the cold dark basement, and leave it until April. Then bring it up to light and give it a bit of water. This I did the next spring. Soon I had sprouts: seemingly from nowhere! Again all summer I enjoyed it blooming lushly. This fall I brought the whole pot in again. When the leaves dropped off I let it dry out. After having the plant almost 2 seasons, now I could find tubers. They are still small, each one less than an inch: closer to 3 /4.

I uses to live in San Francisco and had no problems with begonias growing under a porch. They always bloomed profusely and tubers always got bigger each year. Even the seeds i started in march of 2011 made tubers the size of a baseball. Albeit, we have a long growing season and the right temps. I gave them all up and moved to MA and boy is gardening different.

I started with Blackmore and Langdon seeds feb of 2013 indoors in Boston. Those that survived the move outside all created tubers the size of a peanut to the size of a golf all. Out of about 100 seedlings, I culled out about half that did not have double blooms and the next spring, only about 20 made it. I kept them too cool in the basement. None bloomed summer of 2014. Mainly because I used regular topsoil with some weird mulch incorporated. They did all survive and their tubers were slightly bigger.

I have started more Blackmore and Langdon seeds.mi started a batch dec 15 2014 and about 100 have been reported into 50 cell trays. I just started another batch last week just for backup. They grew really well when I had them under a 4foot shoplight on a shelf above the stove but started dying and damping off when i moved them to the basement with no bottom heat.

My advice is to start very early if you want tubers and enough time to evaluate flowers to cull, being feb a the latestThey generally create tubers in the fall when day length decreases so they need enough leaves and a big enough root system to do that by September. Also give them bottom heat and use a looserepackaged potting mix. I made the mistake of potting them up in whatever was around only to find the the pH of the black mulch I used was close to 7.5