I am also interested in doing the same thing. I absolutely love these trees and am determined to get them to work in zone 4. I have done quite a bit of research and the three I have found to be most hardy are Emperor I (it leafs out later than others for frost safety), Robinson Red, and Korean maple. I live in Idaho and it looks like we are in the same zone. I actually have planted one outside 'Emperor I' that I am going to try to 'winterize' for the first time. I have another one called 'Robinson Red' I have coming mail order. I learned about from this site that is suppose to be cold hardier than some others. I am planning on keeping the Robinson Red in a pot for a few years then move it and plant it outside permanantly. Next spring I want to buy the Korean maple and plant it next to my house. I am hoping with some TLC I can grow these outside in the ground. Anyway--my plan is to wait until the cold weather comes and they go dormant then move it into my garage and wrap the base in a few blankets and put it up next to an interior wall. I think the sunroom might work. My only concern would be giving the maple 'sunroom' conditions might be too warm. I'm imagining the sunroom if it has all the windows I'm picturing, it would be too warm. I have also read people will bury the pot in the ground outside and cover with leaves/mulch. One person I read did put it in an unheated room upstairs and had success. The Emperor I have outside I am planning on wrapping with wire cage and the overwrapping with burlap. Others have given me feedback of success with that. (You could see my link under yours about winterizing maples). Anyway--just my two cents. I am definitely not a pro--just trying to soak up all the info from others I can get too!

I actually did a little more research after my original post. I found one place that said in order for them to be sufficiently dormant they need below 50 degrees for forty days. My sunroom is west-facing but it does get quite cold in the winter....I'm thinking it might actually work. I'm going to give it a try. I did think about putting them in the garage, but I know I'd be better at watering them if they were in the sunroom. We'll see how it goes....thanks for your comments.

No problem. Do you know how often they need to be watered during the winter?

Carrie,

I lived in Idaho before, and there are many climates there. What part do you live in? I lived in Rigby, Twin Falls, and Weiser.

I think the most important thing for you will be insulating the root zone and protecting the stems from dessicating winds. Most of Idaho is VERY windy, so I would wrap all my JMs with burlap for the winter. Plants outside will "freeze-dry" if the ground is frozen and the cold winds draw the moisture out of the stems. The roots can't take up moisture to replace what is being lost, and the stems are killed off - so wrapping is the best bet.

Some good mulch around the roots should help out, and then the snow should do the rest to protect them from the bitter cold. Late frosts may indeed be an issue, depending on where you live.

JMs should not be allowed to have their roots dry out. Pots should be kept slightly moist. Just slightly. You don't want them bone dry but you don't want them soggy either. Put a finger in the soil and if its getting dry, give it a few sips of water.

Regards,
K4

Kaitain4,

I live in Idaho Falls and you're right it is very windy. Do you think I should wrap it with a frost-free fabric that they carry here at the nursery and then the Burlap? Did you grow JM's here in Idaho? I would love to know and know what you did.

Thanks!

Carrie

They shouldn't need much water once the leaves fall off. Maybe a couple of times over the winter.

One thing to watch for with the sunroom is it is going to start warming up in the spring well before the plant could be safely put outside. My sunroom can easily get into the 70's with the late March sun which could cause the plant to come out of dormancy and well before the last freeze date. You might have to consider opening the windows during the day and even at night if it stays above freezing.