ketsui73 said:
Guys thanks for the discussion on potted tree aloes, I have bookmarked the pages for reference.
Evan, it's always going to be better to plant in the ground . Nobody is going to disagree with that . Thing is for me (and lots of other people all over the world ) our weather is not going to allow that option with the vast majority of these plants. So I am trying to figure out what's possible with pots ,when going in the ground is not an option 
Thijs you read my mind on the plicatilis , the feasibility of that was going to be my next question to baja . They do turn up from time to time here so I will keep an eye out 
As you all know I have a lot of tabletop aloes, but I would love to have one larger tree like aloe if I could manage it
We have started discussions on whether or not to put an orangery on the back of our house in a year or two . This would open up the possibility of some large potted plants for me . I prefer this idea to a greenhouse because I get the right orientation (se facing with lots of summer sun) as apposed to east facing which is what a greenhouse would have to be . It would also be easier to keep at the right temperature. I would have less room to expand my collection, but I would be making the most of my conditions so the few plants I got would do better.
Due to the nature of our weather here the growing window is much reduced . So 10 years in a pot for you guys could be a lot longer here
Again thanks to you all for your input 
Steve
@ketsui73
I have family members in the Netherlands who have what we would call an Arizona room here. Here that is usually when people put actual walls and a roof (if not already there) on what would have been the back or side patio of their house. I have not seen it with sunlight friendly roofs here, but in the Netherlands the roof is made up of several large skylights to provide as much light as possible. They grow some Aloes and Agaves, but nothing like the obsessed collectors that we are.
Theirs is set up in such a way that in summer the doors to it can essentially be kept open full time without compromising the rest of the house. Allow for growing a bunch of plants that would normally not be feasible in their climate, but even with all the windows their potted Agaves do see some low light effects in their growth each winter.
With regards to plicatilis, it is always hard to risk what is likely to be an expensive plant, but I seem to remember a British member on a different forum mentioning that he left his plicatilis outside this winter stuffed in a somewhat protected corner of his back yard to see how it would do and that it was so far so good. I think he lives in London so he may have some heat island effects going that you might not get outside of the City, but I think it was his intention to see if it could lead to him putting it in the ground.
What I have read about plicatilis suggests it seems to enjoy wet cold winters (now cold for South Africa and cold for the UK could mean wildly different things) and hot dry summers. It would seem to me the latter is harder for you to manage than the former, but it would suggest that if you were ever going to try a tree aloe type (I know Kumara) in the ground where you are at, this might be it. In my experience in the ground plants tend to deal with low light conditions better than in pot plants (given that most of my back yard Aloes are grown in complete shade from mid Fall to mid Spring, and look none the worse for it).
You would probably have to work with a raised bed type setup with the fastest draining soil you could find/make - so lots of coarse components and then have some ways of protecting it from any of the truly hard freezes you might see.
It may be a total disaster, but from what I have seen posted by members of Agaveville who live in the UK and some in the Netherlands with the right planting considerations it is possible to really push the boundaries of what would seem possible.
