Hey Jim!!!
The BGI has a beautiful Gallery and lots of info.. I am a z7 and over winter several outside with a heavy mulch..Of course I always take cuttings just in case...The biggest threat for me is root rot..Under various conditions they can become tree size in a season.. Here is a link they offers great pic's and some wonderful info.. I hope you will let us know what you are gonna plant and of course we love pic's..
Have a Very Blessed Day!
Chena

Here is a link that might be useful: BGI

Hi Jim,
Yes they can get tree sized in a pot. There's someone that posts here, can't remember who that I think is in Canada whose container brugs are over 10'. My tallest ones are about 8'. This is the first year that I'm wintering them over inground so I'll see if they make it. I don't know how deep their roots grow but I'm guessing pretty deep. I get roots coming out of the bottom of a 25 gallon container in no time. Of the varieties you mentioned I know that Charles Grimaldi and Frosty Pink are extremely hardy. Those are two of the three varieties that I left in the ground. You should have no problem with root damage in your zone. I don't know what your winter temps are but a frost will kill back the above ground growth. I don't know of any books but BGI that Chena mentioned and ABADS have good info and a beautiful photo gallery. Good luck with your garden.
Karyn

There is a good book out by Ulrike and Hans-Georg Preissel
Brugmansia and Datura Angles Trumpets and Thorn Apples. It has a lot of really good information and lots of pictures. I had to order it from but you may be able to find it in a good book store.
As for Associations The 2 I know of are ABADS and BGI both give you access to galleries and huge amounts of information. BGI gives you three seed crosses and Pollen per quarter with your 1 year membership. ABADS also has seed crosses at $2.00 per cross and free pollen (you pay postage. IMO both are worth joining.
In my zone (9b) they will come back from the roots

In southern MS, pretty much all brugs should be hardy in the ground for you. The topgrowth dies back after more than 4-6 hours at 27 degrees or less, but the rootball can survive longer, colder temps---as long as they're not wet. Wet + cold = rot.

Potted brugs generally grow more slowly than ones planted in-ground, but they can eventaully get quite big. But remember, the soil in pots gets colder/freezes quicker than the soil in the ground, so unless you plant on bringing that big pot indoors, you have a higher risk of losing the brug to the winter cold. The soil in pots also gets hotter during the summer, and requires more frequent watering.

Then there's the 'bucket method', which I use for my more temper brugs, chiefly those with Versicolor genes. I take a 3-gallon bucket and drill several 1" holes around the sides, but NOT in the bottom. I plant the brug in the b ucket, then plant bucket and all into the ground. Come fall, I cut around the outside of the bucket and lift the whole plant for overwintering in my greenhouse. I cut back the top just what's needed in order to get it inside, but I do strip off all the leaves. They generally drop them all anyway, and removing them while still outside eliminates the risk of bringing in pest eggs on them. I think it also helps the plant deal with the shock of root-pruning, by giving it a little chance to recover before it has to support the water needs of full-sized leaves.

My in-ground brugs have gotten bigger each year. The oldest one, a nameless, seed-grown white, puts tp about a dozen trunks each year now, and they usually make it to 10-12' before first frost.

Brugs aren't all that deeply rooted, I've learned from digging them up. They spread out pretty wide, but not deep, and they have a tendancy to break or blow over in high winds. One way to avoid damage when you're expecting strong winds (like when there's a tropical storm coming) is to remove most of the big leaves. Brugs drop and replace leaves constantly, so this doesn't seem to hurt them.

Of the ones you mention, I've had CG and Frosty Pink in the ground here sor several years now. Both are quite hardy and heavy, work-horse bloomers. I find they're happiest here with direct sun from dawn to mid-day, then bright, indirect light until late afternoon.