Hollow trunk in Fuji Apple tree

Hi folks,

We recently moved in to a house in Northern California that had an old Fuji Apple tree in the backyard. Since then one of the three of its trunks developed a rot of sorts that effectively killed that trunk in the last few months despite all my attempts. The other two trunks seem healthy and producing plenty leaves and flowering so far but we’d hate to have the rot spread to those healthy trunks. Today I finally cut the dead trunk, and to my surprise, there was a large hole in the middle that is going down at least 12-15 inches.

I’d love to get your help on how to save this tree as it became a sentimental family project/goal to make sure it survives. How should we deal with this hole in the dead trunk? I read in prior threads advice on maybe making a V cut or drill holes for water drainage but given how deep this hollow hole is, it effectively goes under the ground level so cutting/drilling may not be as effective. Should we fill it or.just cover it? Also should we spray the inside with an fungicide of sorts to keep it healthy?

Thanks for all your help in advance.



I see a lot of people using spray foam to fill holes in trees. Never tried it myself, but appears to work. The other two trunks look rough as well.


Welcome to the growing fruit group Leo. I don’t have any advice on how to save the Fuji tree but I’m sure several others can help that have experieced with similar issues. Even with the problem I’m guessing that the other two trunks will live a long time. This might not be a problem but have you confirmed that the two remaining trunks are Fuji and not growing from the root stock?


the left stem seems to have a large split in it.

I think it would be a good idea to fix the cuase, instead of looking for the right band-aid.

Did the previous owners make large pruning cuts on the tree? (usualy cutting into thick large branches makes it hard for the tree to heal or cut off those wounds, and thus stuff can get into the wood that hollows it out.
Especially if they cut behind the branch collar. (line around the branche where it splits of from the larger branch)

Could you post some pictures of the damage to the existing trunks? and maybe of the whole tree?

Edit; Just saw Auburn’s post.
He makes an excelent point! those 2 remaining trunks seem to come from the rootstock. (they come from the gound/low) This could have been a fuji tree that was planted to low and own rooted. In that case, those remaining trunks could verry well also be fuji.
But id pay special attention to the fruits your getting of those 2 remaining trunks this year.

There is a chance the tree will trow up more suckers. (smal branches coming from the ground) Id keep maybe 1 or 2 of them. To maybe grow up as a replacement for the existing trunks if they are damaged. (damage on existing trunks is hard to see. Left trunk seems to have a long/deep split. but it could just be the picture angle)


First of all, foams and other wound dressings are generally considered useless according to extensive and now long established research. Secondly, it is impossible for us to diagnose your problem because it may well be a pathogen that requires microscopic investigation by a plant pathologist.

The good news is that UC Davis performs this kind of service for a reasonable price and you can make contact with them through your county cooperative extension and ask for help. They likely have a horticulturist on staff who may be aware of existing diseases in your area that may be the culprit and that person may suggest submitting a sample for a more accurate diagnosis.

My original take on the photo was that the main tree had died and those were suckers coming from beneath the graft of the rootstock. Trees are not generally trained to have 3 competing leaders starting just above the graft. But you say the tree is a Fuji- have you tasted the apples from the still living competing trunks of the tree? The one that died looks to be the original tree.

Fujis and all other named apple varieties are grafted to different trees that become the rootstock in the nursery they are propagated- they aren’t started from seeds.

Unfortunately, if the problem is fungal and based in the roots, there may be no cure but you should probably find out. You need to know if there is a killing fungal disease inhabiting you soil.


Thank you so much folks for your quick responses, I really appreciate all these insights and advice, especially as a newbie to fruit growing and to this forum! Here’s a few more data points to answer/clarify the questions that you raised and also adding more pictures of the whole tree:

  • Indeed, the rest of the two trunks are rootstock and all apples seem to be Fuji. During the last season, those trunks produced what seemed to us like plenty good fruit - something like 30+ lbs (except the now dead and the cut trunk, which gave us nothing)
  • However as you also noticed the other trunks also have quite a bit of cracks. I am hoping that whatever fungus got to the dead trunk, it’s not bothering the other trunks just yet though.
  • Sadly, the previous owner did not seem to care much about anything in the yard, so it’s likely the tree was neglected for years and pruned in wrong way that resulted in this state. The tree is also planted in an unfortunate place but from what we can tell, it spread its roots fairly well under the concrete and into other parts of the yard.
  • Alan, the idea to send a soil sample to UC Davis is a great idea, thanks for that. I’ll dig in more to find out how that works.

Assuming that they find fungus in the soil, what’s the best I can do? Is regular fungicide spray useful at all at this point? Anything I can do to extend her life? Also, would me spraying fungicide into that hole help at all or hurt things?

Thanks again,


One more:


Actually, I’m not sure they will want a soil sample, they may want a piece of root or wood just above the soil line, I don’t know. That’s why I suggested you contact your cooperative extension for guidance.

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I think the best you could do is start growing a replacement. Trees can limp for years on injuries like these so enjoy the apples it gives, you, graft from your current tree into a rootstock and into a very large pot, and eventually you will have a replacement big enough to fruit on its own. Better yet; as a scion graft the replacement will be 100% the same tree you will be taking out, an identical clone as far as the genetics go.


I agree with Don. Plant your replacement and milk this one for as long as it last. Hopefully it lives long enough for the new one to start fruiting.


This tree is a goner. The lack of heart wood is probably why there are so many cracks. It can no longer support its own weight. The photo looks like the rot goes all the way into the crown. I cut out a Fuji last year for the same reason.
The Geneva rootstocks are supposed to be resistant to apple replant disease, so maybe you can find a Fuji on one of the more vigorous Geneva rootstocks. If you plant close to your Fuji, you can cut down the old tree in a few years and hope no one notices. Like buying a new goldfish before the kids get home from school.

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Another additional possibility. Get rid of the rocks and mulch it with woodchips. It seems to be poorly nourished as well. Perhaps try some 10-10-10 fertilizer this spring and fall and see if some vigor returns. I don’t know your climate, but perhaps summer drip irrigation is also needed. I agree that a plan b is to graft a new tree next spring for a backup. Also maybe don’t let it fruit this year, or lessen the fruit load for a healing year.

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I like your advice.

That’s an old tree. Enjoy it while you can.

I had a crabapple just like that. An old Radiant. Every May the blooms were so glorious, and I’d think - how many more years? I had to take it out last year, but I don’t regret keeping it.


If the tree is growing vigorously it might just outlive you. I manage century old apple trees whose trunks are more than half hollowed out with rot, but then, I’m not familiar with the cracking symptom. However, anyone that says that is an old tree doesn’t live in the northeast- the tree is probably only about 35 years old and I’ve managed scores of semi-dwarf trees still going strong after a century and trees with seedling rootstocks that might be pushing towards two. .

I can’t diagnose its condition without seeing its new growth in spring, and even then it wouldn’t be very reliable without knowing what caused the center section to die or the cause of the cracks. It didn’t die because it had a rotten center, something had to have happened to its vascular sheaf- probably just the cambium.

I really think Leo should invest the $35 or so to get a real diagnosis, especially before he starts planting new trees in the vicinity.


Thank you all for your wisdom and advice on this - I very much appreciate it. Given the tree is in decline, we will try to take care of it as well as we can and enjoy it as long as she survives. I’m hoping it will be good till next winter where I can collect a scion for a graft. And yes, I will definitely spend the money on the analysis.

In the meantime, any strong opinions on spraying copper sulfate in the hollow trunk and filling it up with close cell foam? Or just spray it and let it be? I really worry about water getting trapped there and worsening the rot. I know research is divided on this, but if it won’t hurt the tree, I am willing to give it a shot.


i would not spray or fill up the hollow spot.

At most i’d make a raincap.

Any possibly useful treatments should come with the diagnosis- if the pathologist identifies anything. I suggest waiting until you have the information needed to target any possible pest.

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Assuming you still desire to save it, you may want to clean out enough soil and rocks around it to see how much you need to remove to get down to solid wood. Then either cut or grind out the rotted materials. Once you have it out, blow out all debris with a power blower. Then I would spray the entire trunk including every bark split with copper sulfate for 2-3 applications. Once dry I would use Tangelfoot pruning sealer to seal every hole back to the edge of healthy bark.
Apple trees are pretty tough, if you want new limbs at a lower level, try next spring to use side grafts to add dormant scions you save this winter. Some trees will automatically grow latent bud limbs just below a side graft. Good luck
Kent, wa

I wasn’t kidding, a graft into a new rootstock is the exact same tree. Different shape but on everything that matters, the exact same tree lives on.