I had a pomegranate for over 35 years. At some temperature colder than 25 F they will be killed outright. Key with cold is duration. If the cold lasts long enough to freezes solid the pot they are in, they can be killed by temps as high as +25 F. I found out the hard way. I used to leave mine outside to get a few frosts of 29F. I forgot once and +17 F killed it dead.
I got my best growth moving it to my well house. A totally dark room that stayed colder than 40 F, and stays warmer than 32 F. Not many have well houses anymore, but your garage might work. It needs zero light while it has no leaves. It rended to wake up early, usually February. I would then move it to the lights set up I used for my orchids. Growth made indoors would be weak because of the lower light intensity. As soon as safe from frost it would go outside. I would give it a hard pruning to eliminate all but the first internode of indoors growth. Overall this worked "best".
However the first 20 years I had my pomegranate, I did exactly as
@Carol 83 - Leave it outside to first light frost, then bring it in to over winter either on a windowsill, or under lights in the orchid collection. THIS WORKED. It might not have been the best, but it worked well enough I kept the tree alive and growing for 20+ years. A trick I found to make this work better. I would stop pruning the pomegranate about middle of summer, say August 1 to Aug 15, in my climate. It would then come inside in October, fairly overgrown. It would sit, semi-dormant for the winter, putting on some weak growth that would have ''too long'' of internodes due to being in relatively low light. When it was put outside for the next summer, after last frost. I would cut it back sharply at that time. Cut back into the growth from the previous August. Last frost was May 15 to May 31. So first week of June I would prune back into the growth that had been left on since August the previous summer. This way all the growth that was kept had short internodes because it was ''made in the sun of summer''. It worked fine. THe overall size of my tree did not increase as fast as a tree grown in California, but it grew enough I was happy with it. Every summer I would get flowers. I loved it. So Carol's method is ''good enough''.
Pomegranate is a great beginner species for bonsai, because they are resilient plants. They will forgive the occasional ''forgot to water'', they will tolerate a frost, if you forget to bring them into protection. As long as you give them sun, they are fairly bullet proof as a tree goes. In terms of drought tolerant, I once let it dry out in middle of summer, maybe 4 or 5 days after it should have been watered. Every leaf shrivelled up and died. Kept it slightly damp for a month afterwards and bingo, it started growing again.
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