Years ago we used to be able to buy dwarf citrus trees to grow indoors in Canada - and I did and they did well even in very cold areas if one tended to them properly and ensured they had a good sunny spot. However, since I returned to Canada a few years ago I have not been able to find a source for same up here any more. I think there have been regulations prohibiting imports put in place. I hope they lighten up on those in the coming years (seeds are now allowed across the border I understand so things 'can' change).
I do know that if one is patient one actually can grow citrus plants from seeds found in a (probably organic) fruit but I am not sure I have the fortitude for that endeavour. It is a lot of work to get to the actual germination 'seed' part inside what we call the 'seed' - and it must be done with care I gather, and there is a high failure rate - but it can be done. I lost the link but I found a guy once who had a blog (and Youtube videos) of an upstairs bedroom where he kept many, many overgrown plants of all types that he planted after carefully harvesting the seeds - and they actually produced. He had citrus of all kinds and avocadoes and pineapples - you name it.
