Can I grow bonsai indoors?

I've been hanging around Reddit's bonsai group for a while now and, despite my early reservations after receiving some pretty harsh criticism, I'm finding it a really good place to learn.

A topic that comes up for a lot of debate there is whether it's possible to grow bonsai indoors. Some people insist that it can't be done, while others are more open-minded about the idea. What is certain is that some species cannot survive for long indoors and many newbies are in for a shock when they discover that their recently-acquired Juniper bonsai is dead or dying because they were misled into thinking that it could be kept on their desk.

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I confess that when I first became interested in bonsai in around the year 2000, I too wanted to grow my little trees indoors. I knew very little about plants in general back then, but I'd already come across a book about indoor bonsai, so I had no reason to doubt that it could be done. One of my problems was that there weren't too many sunny spots inside my house and I hadn't heard of grow-lamps back then. My early attempts were consigned to the sunniest spot I could find - in the kitchen.

My first two trees were an Azalea and a Ficus, and with the ignorance of a beginner, the first thing I did was plant them in bonsai pots. Neither survived very long. I can't say for sure that it was being indoors that killed the Azalea as I'm sure I must have made other mistakes too. The Ficus, however, certainly could have survived inside if I'd cared for it properly, and I know that its death was entirely due to stupidity on my part.

I was not deterred, but refrained from putting my next batch of trees into bonsai pots and didn't even put much effort into styling them. In fact they spent their early years living with me as house plants. I still have two Ficuses I bought during that period. They now live outside and are slowly being trained into bonsai.

Another early acquisition which survived my early abuse was an Acacia Burkei, a tree which it has always been claimed needs to be outdoors. I've proved that they can survive on a sunny windowsill, but keeping mine there had disastrous consequences, if only because I gave it minimal care. Actually that tree did a lot more than survive, it thrived there... but in so doing the branches grew through the burglar bars covering the windows and when I finally wanted to move the tree, I was forced to cut off all the branches and start over. Had the tree been a Juniper, that would have been a death sentence. My Acacia now lives outdoors too and has developed some decent new branching.

Everything changed when I joined my club in late 2007. That was when I started to realise that even trees which can survive indoors are better off being outside when the weather allows.

Shortly after joining the club I started an experiment to see how keeping a tree indoors affected its growth. I started with these two young Ficus Benjamina cuttings:

Two cuttings at start of experiment

The cutting in the green pot was kept outdoors, while the one in the red pot was kept in my kitchen in rather poor light. After six months the difference is very visible in terms of both size and leaf quality. The leaves look so different that they don't even look like the same species.

Two cuttings at end of experiment - five months later

When the experiment ended I attempted to put some shape into the indoor tree, but in its weakened state the shock of wiring was too much for it and it died. The outdoor tree was with me for several years before I sold it at our club show. To the best of my knowledge it is still alive.