If the green leaves are all on a branch that originates from near the soil level (below the graft), you have a root sucker being sent up by the rootstock. This should be removed immediately. If the green leaves are growing from a single branch or on an area of a single branch originating from the upper parts of the tree (above the graft), you probably have reversion or a sport. Revisions should be removed so that they don't "take over" the tree. Other possibilities include variation due to the amount of light/shade, differentiation between older and newer leaves, etc. As dibbit indicated, there are lots of possibilities. As for the spots, there are untold numbers of possibilities and pictures would probably help a lot.

I'm in zone 5 Ottawa,Canada. Zone 4 for you in the US. They used to say you couldn't grow J.maples around here. But for 20 years I always could, and have never lost any, except 2 variegated ones. I have about 25 varieties, a sort of J. maple forest in my back yard & I am running out of room. Good thing they are dwarf trees, unlike our native maples that grow to 50 ft. I wholesale them from (grown in)BC, zone 7-8. They do not loose hardiness by grafting and propagating in a milder climate. The hardiness is built into the plant. I will say that they can sometimes be slow to establish, and this is the important part. Any tree should be planted early and well cared for in the first season, so it is well established going into it's first winter. I don't believe in bare root trees doing well, too slow to establish, or over wintering in a pot. They should always be planted in the ground and well mulched. I do think they prefer a more acidic soil. Ours is neutral approx. 6-7ph, so I spread sulphur everywhere every couple of years to acidify a little.(I don't like pink hydrangeas, prefer blue) I saw a study once, out of U of Michigan I think, where when they tested plants, and they found that plants growing in acidic soil seemed a little hardier than the same plants growing in more alkaline soils. In the past I have used geo-textile fleece as a winter cover for the first few winters, but snow makes a great insulator as well. I get a bit of tip dieback sometimes, but it doesn't matter since they grow back very well, as if they were pruned. There is a sort of wilt going around in J. maples lately, others have noticed as well. It doesn't hurt the tree, it just attacks some of the newest growing tips as they are finished flushing out in summer....sort of self pruning. We regularly get to minus 22 celcius (-10 far.)here most winters, with minimal problems. Even with last winter, the worst in 20 yrs., there were no losses. The only damage I ever notice is the heavy snow pack in spring, will sometimes crack the weeping types as it weighs them down and melts. Variegated types do seem less hardy, possibly due to the fact that variegation is a mutation and therefore weaker. Red and green types are perfectly hardy. They all seem hardier as they get older. thanks, Rich

Looks like it has a decent amount of growth down low. Roots must bebmore cold hardy than the top. Do you remember what cultivar it is? Seem you have discovered exactly how cold a winter it can survive.

PM2, problem with HD is that individual stores don't know what they'll receive untill truck will be there. Even when they got their shipment invoice will say something like 'Assorted japanese Maples' and someone has to go out and physically check what tags on a plants says. Which is not going to happen, as you may guess :-) In my neck of the woods the following cultivars are pretty much common parts of the mix: 'Inaba Shidare', 'Tamukeyama', 'Red Select', 'Viridis', 'Butterfly' and 'Sango Kaku'. However, when grower for whatever reason can't fullfill order's quantity with 'common' plants it will throw in something from his 'premium' stock...but to get them you should be lucky to be the one of the first who sees them...and know what you are looking at :-) That's is how I got my 'Koto Hime' and 'Oridono Nishiki' (which at first glance looks like a 'Butterfly' reverting to original green form).