I had a tray of seedlings that I dug in fall last year and overwintered exposed in 4" pots. They were 1st year like yours ans the same size. About 90% or better survived. In your zone I would suspect you would have to protect them and the cellar sounds like the easiest way. After leaf drop--you can even have them out for a few small freezes--bring them into the cellar. Leaving them out as long as possible will ensure the plants shut down in case cellar temps aren't initially ideal. Effective dormant temps can fluctuate from just above freezing to the low 50's for around 6-8 weeks. Once the risk of a hard freeze has past, just bring them back outside on a patio or semi-protected area, and then out into the open.

The biggest problem you will have is soil moisture. Too wet can cause root rot and if they dry out you risk losing the plant. Keep and eye on them and water sparingly if they seem dry. No light is required in dormancy. Have fun.

Michael

I have kept potted maples in my unheated/unattached garage with good success. I have also kept potted maples in my unheated cellar with poor results. One year, my tree broke dormancy way too early because the cellar temp was consistently above 45F. Another year, mice (that love the dry laid stone foundation in my 200yr old house) actually ate 3 of my trees and killed them. I would opt to place them in a corner of your garage and spread mulch around/over the pots almost up to the stems if you can. If the pots freeze, thats ok...you won't have to water then. If the soil is not frozen, water cautiously...too much water will rot the root system.

Dave

PS if you have mice, set some traps, as well

I over wintered seedlings last year in my unheated, detached garage along with my container trees. We also had an exceptionally cold winter. Everything survived just fine. I made sure they were damp when it froze, and watered when it was warm enough to thaw. I didn't take any other measures, like mulching, but you are in a zone colder, so it might not be a bad idea. We didn't hit 0 last year, but came close and had sustained cold. Outside with the wind, anything in a container would have succombed. I waited until we had a forecast of 15 degrees to bring them in. Everything in the ground did just fine, too.

I had to remove a big japanese maple for addition of my new porch last year. There was one volunteer seedling, about 2 in tall, coming up. I moved it to a rather protected bed next to my house and built a "fence" around it (using plastic edging of same height) to afford it some protection from fierce winter winds. It survived winter beautifully and is about 6 in tall now. I'm about to move it to it's permant location in back of my yard. Thinking of using a pop bottle cloche when it gets really cold.

somebody asked the same question, maybe she can use this posting

Follow-up: turned out that I had slightly under-estimated the number of seedlings, since I'd just grabbed buckets of leaf duff with them buried in it. There were 68 all told, and every one different in leaf shape and color. (Is this the norm?)

I potted them up in some pretty bad "loam" delivered by a contractor for something else, and got them established before winter. All but one survived potting. I have an unheated greenhouse/solarium attached to the house, and put them out there until November, when the leaves dropped. Then moved them into complete shade under the table to prevent sun scald and freeze-thaw. Kept them moist - probably too wet - and put them up in the sun again in March. All survived except for two that a chipmunk nibbled and two others that may hove gotten too wet or dry. They are out in open ground now, and as they reach 16" I'm transplanting them to final locations (or giving away). The forty or so I'll be leaving in the ground this year I'll probably mulch with wood chips, unless there's a better suggestion.

Thanks for all the good advice!