regarding pomegranate, I understand that they are subtropical - does that mean I can grow them indefinitely inside (I have no outdoors location )
or will they succumb to lack of dormancy?
I know that they will supposedly do *better* with a breif cold spell (from what I read at least) but is it required the way it is for other trees (like pines etc)?
)I would say at least 3+ months. I would leave it in the garage or unheated room until it shows signs of bud breaking for best results. And it is also important to remember to water it throughout dormancy, and so it is unlikly you would forget about it. I have never actual tried to grow pomogranate, so it is a good idea to research all you can on them.
Some do keep them without the dormancy period, but most experienced keepers and the literature support that after two years of non-dormancy, the tree will be in pretty bad shape and will usually die. One thing you might want to consider is, instead of investing in a cold room, getting a small refrigerator and installing a light and slight ventilation. There are specialist boxes like this specifically for this purpose, but they're expensive. As I've learned in the marine aquarium hobby, sometimes you can produce the same effects for much less money, even if the setup may not be quite as pretty (although this is not necessarily the case).