This time of year you will see a lot of small evergreens being sold as small indoor Christmas trees. With limited exceptions, however, live evergreens are not really suitable for indoor growing.
If you have ever tried to grow one of those juniper bonsai that seem to be very popular this time of year, you know the problem. They will grow fine for awhile in our heated, dry homes, but eventually they succumb to something-usually it’s mites, although they are often too small to see. The plant just looks like it dried out and died.
Other small evergreens, often sold with lights and ornaments already attached, are Alberta spruce. They make adorable little live trees–but they are then very difficult to transition back outdoors into a cold climate and plant in the spring.
Then there are the non-hardy cypress and pines that we get up here in the frozen north. They are lovely and beautiful but what, exactly are we supposed to do with them? They can’t be grown in containers forever?
So if you would like to have a small, live evergreen indoors, the Norfolk Island Pine is probably your best choice. It’s easy to care for, it doesn’t mind being grown as a tropical indoor plant, and it supports ornaments.
A caution or two: it will put on a new layer of branches every year. So eventually, they get large.
Also as you can see, they are often sold with multiple trees per pot. For best growth habit, separate them out now. I may have waited a little too long already. I think I actually have 3 in that pot!
And while I have read that they can be susceptible to mites, I have never really had any trouble with any that I have grown. I grow them in an east or west window–wherever there’s room.
These little trees are generally readily available this time of year. If you want a small, live tabletop tree, this is definitely the one to choose.
Gardendaze 
The most popular sorts have rather pendulous growth. I am not certain if the more rigid sorts are even available anymore. In the garden, the rigid sort grow very straightly and symmetrically, and look as if they were ‘built’ into their landscape, like a utility tower or antenna. They might make better Christmas trees, but then, they might be too symmetrical for some people’s taste. I really do not know, and they may be pendulous while young.
Hmm. I am not sure that I have ever seen one of these “in the wild,” as I would jokingly call it. I have seen most of the other things that I grow as “house” plants and at times they are almost impossible to recognize. Your point recently about bougainvillea, for example–I have grow them, and had them flower quite nicely in containers for me. But when I see the “real thing ” that’s when I realize that what I am growing is just a pale shade of the real plant. I do tend to prefer these large flowering tropical hibiscus cultivars to the old-fashioned plants. But I doubt that they would form the nice shrubby bushes I have seen in warmer climates.
Karla