LOL!! That's a bunch of info you are requesting! But I grow all my JM's in containers so I'll do my best to answer your questions.

1) The single most important consideration for growing JM's in containers long term is the potting mix. They need a fast draining mix and one that holds up well over time so I'd suggest a bark-based mix like the 5-1-1 or the gritty mix discussed at length on the Container Gardening forum. Stay away from Miracle Gro and others of its ilk!!

2) I use a controlled release fertilizer (CRF) when I pot them up. Osmocote is the brand I use but any similar product will work. I also topdress with more each spring for already potted maples. I also supplement a few times each growing season with a liquid fert (Dyna Gro's GROW) at half strength because that contains a full range of trace elements the plants need and that other ferts tend to omit.

3) Growing "forever" in containers is certainly possible but not as simple as it sounds :-) You will need to refresh/replace the potting soil periodically - it doesn't hold up forever and starts to break down after about 2-3 seasons. And unless you are potting up into larger sized containers, you will need to prune the roots periodically to contain the size and rejuvenate the system of fine feeder roots that nourish the tree. I usually coordinate the repotting and root pruning to the same schedule, to eliminate too much unnecessary handling.

Finally, you need to pay close attention to the watering needs of trees in containers, particularly when you are using a fast draining potting mix. I live in a cool but very dry summer climate so I water about every two to three days in summer. In hotter climates you may need to address even more frequently. And you want to be conscious of winter cold. Containerized plants are more sensitive to cold temperatures so if temperatures fall into the 20's and remain there for more than a couple of nights, you might want to protect the containers. I gather mine together to create a small microclimate but wrapping with bubble wrap or mulching with straw, etc. can help. JM roots will be damaged at around 25F.

Gardengal, thank you for so much great information!

I am a hosta person at heart (about 600, yes, it is a disease and there is no known cure) and the soil combo I use for them is a lot like this. I also have to keep an eye on them as far as the soil decomposing so I'm used to that. It's a lot of work but we have to keep our babies happy. Cutting hosta roots is a huge no no so it is good to know jms can take a bit. I will look at the Container Gardening site, don't know why I haven't thought of that.

What is the formulation for the Osmocote that you use? Hostas of course are heavy on nitrogen but our society uses a combo that has trace minerals also. I'm guessing jms might not need as much nitrogen?

I also move my pots to our covered patio in the winter. It is very rare for us to have more than one night in a row of temps in 20s. Our prediction was 31 for last night and 30 tonight with possibility of icing so yesterday I moved all the pots into my little building that I use as a greenhouse, along with a lot of hostas that decided to wake up the middle of Feb this year! Their foliage is so tender right now I just couldn't risk it.

Don't you also post on the heuchera site? Folks on there have helped a lot. I have about 50 now, mostly in pots and while a lot don't love our southern summers there are a lot that do well. Villosas are great.

Again, I appreciate the info. It's comforting to know there is help just a click away!

Gloria

I have 97 right now, probably 75 of them still in pots.
I have done all kinds of things, such as bury the pots in the in the ground to protect them during the winter. (Quite successful.)
I have sadly, left several in pots way too long where there roots become a solid, twisted ball. I've root pruned them, and so far some have successfully survived several year in the ground, so we'll see what happens.
When I lost my shade tree, I lost many in pots, but then I've discovered there are a bunch that can take full, unmitigated full Maryland sun.

I just recently learned to fertilize and actually care of my trees in a smarter, more nurturing way. I always just stuck 'em in the ground, but it's worth the time and effort. They're just beautiful.

(I, too, have several 100 hosta and heuchera. Ferns now, too. Seem to go had in hand. Shame I don't have much shade!)