I bought one this spring for $22...mislabled at Lowe's. It was an impulse purchase. After asking around I guess they are known to croak around here. Even a JM expert in IL says they are terrible. Local nursery told me the same thing.

Maybe post a pic and you can get some advice on how to prune. There could be many other factors impacting its performace...so maybe we can spot something from the pic.

As Japanese maples go, the coral bark, 'Sango Kaku', is a bit more fussy. They seem to be less tolerant of the colder zones and many sources will limit them to zone 6. And they do have a greater tendency to some root rots and especially bacterial canker, Pseudomonas, than do most other JM cultivars.

I'd need to see pics of your coral bark to confirm but the upper dieback/leafless branches sounds suspiciously like pseudomonas. Do some research and especially look closely at any photos that display symptoms of this disease for comparison. If caught early enough, it can be controlled but since recommended control involves pruning out all infected material, the tree may not look too great afterwards.

Coral Bark maples are boderline hardy in Z5. It's unlikely your tree has any sort of disease. The most likely explanation is that where protected by snow, the tree survived but succumbed to cold above the snowline.

Check the base of the tree to make sure the new growth is not coming from below the graft. If it is, this means the entire Coral Bark part is gone. If the parts sprouting are from above the graft, prune back to that point and the tree will regrow over the summer.

A screen of burlap or some other material can help boderline Japanese maples survive because it protects the thin bark from winter sun and wind. Such screens won't turn -20 to +10, but they can be a big help, especially for young trees.

MOST JM's are not hardy in my z5 ... it all depends on micro climate.. winter wind.. and winter sun ...

way back when .... my CB died back to snow cover as yours.. and then the second winter .... w/o reliable snow cover died completely ...

give it another week or two .. then cut back the dead...

and hope for the best ... but enjoy the heck out of it.. because .. IMHO .. its a terminal patient ...

if you have a warranty ... you might want to use it to buy something else ...

ken

Concur with the cold susceptibility diagnoses. Hopefully it was on sale.

Dan

As the coral bark is more prone to disease issues than most other JM's, I'm not sure one can automatically rule out this as the cause of the problems.

And it should be relatively easy to determine. Cold damaged stems and branches will be gray or light brown in color and with obviously dead interior wood. Diseased branches will still retain color but with blackened streaking, tips or splotches (the cankers). Interior wood will still be green and pliant but again with discolored spotting to match the exterior.

FWIW, pseudomonas is often seen in response to a cold winter (where the tree is stressed by cold damage) followed by a wet spring. And late spring freezes can also encourage the problem.

Thank you everyone - I had no idea that a) they are so tempermental and b) they were susceptible to pseudomonas (which I've never even heard of!)

After reading all the responses I suspect it was a combination of both winter dieback/wet spring with freezes and the pseudomonas.

Some of the dead branches are pale gray/brown, others are black.

I'll try pruning back to the healthy wood at the bottom and moving it into a more isolated place in case the pseudomonas is contagious.

I just bought a beautiful ulmus hollandica wredei which I may plant in place of the CB maple.

thanks again for your help !!