My bare root arbor day 3ft red maple had about 18 to 24 inches of root if I remember right. I bet if you get that far under them you'll be ok.

If you can wait until fall all the better for their survival %. Do they have any kind of sentimental value or otherwise that makes it a disaster if a few don't make it and you have to order new ones in the fall?

I don't mail order this "late" in the growing season but I move plenty of tough trees around. Personally I think you'll be ok.

Is fall planting recommended for zone 5? I thought Spring planting was better? I don't know...I'm in zone 7b-headed for 8...

ebohatch---I'd call my county extension agent and ask what he advises. Or a local nursery that specializes in jap maples...heck, they may have someone who can move it FOR you at a price!

In suburban zone 6 St. Louis here I do well planting honestly hardy plants in the fall.

Give me a generic Acer Rubrum (Red Maple) that is probably zone 3 hardy and it doesn't seem to car.

When I plant Acer Palmatums (Japanese Maples) I try to do it in the spring. Even the ones listed as zone 5 hardy have a difficult time here the first winter in the ground. Haven't lost one, but they have quite a bit of die back.

ebohatch, are we talking about the more tree like and hardy red maple or the ornamental Japanese Maple? I assumed the larger growing one was what we were talking about.

Woah.
You planted them 4 years ago and they're only 3' tall?
Somethings not right about that.

I'd wait until the trees go dormant to dig (or do it in the early spring before they leaf out) but you may be able to find red maples in pots at the garden centers that are twice the size for under $20. Why bother digging?