It looks like all the healthy growth is coming from the graft understock. I'd cut off the main trunk as close to the soil level as possible. And sterilize any pruning implements after cutting.

The soil is proper for the tree as I understand. It was selected and planted by a very reputable landscape firm that renovated the entire back yard 5 years ago.

Yes - the physical damage is concerning. It started after the second winter -a very severe winter I might add. Thanks.

"It looks like all the healthy growth is coming from the graft understock." I didn't know J maples were grafted onto understock. I will check to see if the leaves are exactly the same on both. Thanks.

All named forms of JMs are propagated asexually, either by grafting or cuttings, with grafting far and away the most common method. And the graft union is apparent in the last photo.

We don't exactly know what "this" is. Might be graft failure, might be a disease, might be mechanical damage. But the understock appears healthy enough.

So gardengal48 I need to take out the main trunk as you said. This is pretty drastic but I realize I need to gather up my courage and do the job. The tree looks sick and unsightly in our main entertaining area. The leaves are already so far compromised that they will not come back. Should I angle the cut to or make it flush and horizontal. Is ground level good or should it be 1 or 2 inches above ground.

As close to the ground as possible - doesn't need to be flush. And at an angle is a good idea to ward against any possible rot setting in.

narrow it down for us.. canada. is kinda large ... big city name ... BC is a bit different that toronto ...etc ...

could there be any issue of zone pushing ....

in my z5 MI ... i have some JMs that are fully winter hardy ...

and every one bogusly sold to me a zone appropriate that werent.. even with winter protection.. failed ... and that could be part of you graft failure suggestion ...

if you had this done by a high end nursery.. what have they suggested the issue is ... im not sure you would have any warranty claim.. but if you did pay for the boat that summer.. the least they could do is talk with you ...

ken

btw: im not seeing the leaf damage in these pix.. im seeing two different trees.. leaf type/shape.. slightly different color ... and im wondering if you simply have a tree that changing shape as it matures.. and you just dont like it ... thats fine.. but its a pruning issue... and though the ultimate prune is basal... to the ground.. seems to me there is a lot of pruning that you could learn to do before you go all paul bunyon in it ...

It is very apparent that the center portion of the tree has some major issues and is declining. And It is also very apparent that the new growth is coming from below ground or the root stock. It is not changing shape - the center portion is slowly dying. Or trying to.

I would not risk leaving the affected portion in place in case it is a serious pathogen. The only pruning that will help this is the removal of the affected center portion.

Make two cuts. The first higher up to remove the weight of the trunk. The second as low as you can go without hurting the root stock sprouts. Don't fight the weight above when you need to make a clean cut down below. The tree you paid for is gone. I have a root stock JM with perfectly lovely leaves.

After removing the main trunk, please post another photo. I'm concerned that you need to prune the rootstock as well to create a tree form.

This is never going to develop into a tree form. It will always remain a short, stubby, multi-stemmed shrub

Are there named or standard root stock regularly used for all the various JMs? At this point training the root stock to tree form might be difficult, but if the root stock is a seed grown Acer palmatum, that is what it is going to want to be.

We have had a dwarf japanese maple for about 12 years and have pruned it to a very sculpted shape over time…it seems to me that when you remove the dead part that you could thin out the multiple stocks and begin developing a more aesthetic shape…..it seems to have partial shade which it definitely needs..and i think it likes to be watered frequently …with adequate room around it for the roots to spread it would be happier….in hope that there is still life in the big trunk i would not completely remove it ..as it could develop more shoots as well…this is how it looks in the spring

The rootstock for JM's is just the straight species. Because of the nature of how it was grafted, the die off or removal of the upper or scion portion rarely ever results in the rootstock taking over to form or be trained into a replacement tree. A replacement shrub, yes. And certainly won't in this case as all the new growth is coming from below ground level (not just below the graft) and there is not enough vigor in any of them to develop into a leader or provide significant erect growth.

We see this with other maple species as well, even those not grafted. If the central trunk/leader is destroyed or removed but the tree still alive, it will produce multiple shoots from the rootstock but none of them vigorous enough to take over as a leader, resulting in healthy shrubby growth but not a true tree form. Pruning doesn't help.

The OP's design requires a tree in that location. If the rootstock can't be trained then it needs to be removed.

It's a rootstock tree now. My neighbor has one that looks just like that. Only bigger. They think their tree magically changed from having red leaves to green one year. Theirs looks OK as far as form goes, but honestly there's nothing great about it. Not worth the effort to take care of it IMO. I would get a new tree. If you can dig up the old one, I would do that. if not, cut it down as far as you can and put roundup on the stump.

I had that same look on the trunk of my trees one year. We had a warm spring followed by a very low cold snap into the 20's. The sap had started rising in the trunk and then froze and expanded .It split the trunks just like that.

My crepe myrtle and ginkgo split and had to be pruned. Quite a few dogwoods and maples of all types around town had the same problem.

Hi Folks, thanks for all the info. I am very content to work with it as a shrub. Designs evolve and flex. It is nature out there not an oil painting. The shrub form will be quite fine and Japanese maple leaves always look beautiful imo. (PS cant use round here and never would it is very illegal and so dangerous for every living thing)

So.......I cut out the main trunk today and using some stakes I tied two of the longer remaining branches into a more vertical position. I only pulled them up by about 6". It looks fine now and very healthy. It was a tragic surgery to perform but the patient is doing well now.

Looking back at the invoice I discovered the tree was an Acer palmatum 'Sango-kaku' (Coral-Bark Maple). :(

Thanks folks for all the hand holding.

I will get a pic and post it soon.

Enjoy your day.

Thanks for the update DB!

Looks great.

Bill

round-up is not illegal in canada (or even alaska), nor is it dangerous to every living thing

it is a non-selective herbicide, if it was illegal you would know as farmers would raise a mighty furor

pretty much every green thing you eat has been sprayed with glyphosate (yes, even organic)

and every red thing/eggs/cheese as well (since all animal feed is sprayed as well), once again you would be keenly aware if glyphosates were very illegal where you live

maybe unfarmed fish is your only out from round-up

yes, your named japanese maple is no more, you have your rootstock though

happy trails

Did anyone mention Roundup?

No. No one said anything about round up. HU-763594092 is confused or just spamming every thread.

I suggested she cut it down and put roundup on the stump. Pretty much any stump killer would work. I just suggested roundup since it's widely available.

I see the mention now. But all that is necessary is to prune out the dying scion. Roundup might end up killing the whole thing if graft and scion are still interconnected, which is likely since the top is not completely dead.