How to extend the life of a hollow apple tree?

My wife and I bought our home three years ago, partly because of the award winning perennial gardens. We've since been converting it to have more edibles and doing a lot of enhancements, but there are a few ancient centerpieces we want to maintain.

One of them is a very old apple (snow apple, most likely) tree that once belonged to an orchard where our home was built 32 years ago. The tree appears healthy, vigorous, and produces a lot of fruit... but I worry. A large portion of the core of the tree is hollow. This is from the removal of very large branches at some point in the past. I've allowed some branches to grow on the outside of the hollow areas to keep this part of the tree biologically active and prevent further decay passively, but I'm at a loss as to what I can do further.

No tree lasts forever, and I fully expect answers like "enjoy it while you can". At the same time, any advice to extend the life of this tree would be greatly appreciated. At least it doesn't look like any small critter has decided to make it a permanent home!

I have had apple trees like this, especially one that I loved as a child (long gone now). It will inevitably collapse; I think your plan of encouraging growth around the holes may help. What you may be able to do is encourage growth from points that are likely to remain intact when a major trunk breaks, so that the tree has a ready starting point for regrowth. Also, pruning to reduce weight on the trunks that are in danger would be wise. I have one or two trees by my driveway where the original trunk is dead and mostly gone, but a sucker took over and is a full-fledged tree now. Obviously you would want to take care with a grafted tree that any trained-up sucker came from the scion section; my trees are either wild or planted by farmers a century plus ago, so no grafting involved. One is a Northern Spy, very tasty

Thanks Glenn!

The history of this area is a bit patchy, but it was originally settled in 1812. I have no idea how old the orchard was, but this is a very old tree. I am afraid that strong winds or heavy fruit might weight too heavily on the existing branches and cause the trunk to split, so I have been pruning the tree back to a bare top. Not quite there yet, as I read that I shouldn't take off more than 30% a year. Next year we should be better, and the weight on the branches will be less. I looked up grafting techniques, but nothing seems to cover grafting scions inside a trunk to fill in the space - so I assume it's not possible or would be like winning the lottery to get something to take hold.

I'd love to graft a portion of this tree to a new apple tree we planted in the yard to keep it going - the fruit is very crisp and a little tart, just what I like for a pick-me-up on an autumn morning. I'd hate to see it go. It's definitely not a grafted tree, it's something unique to itself - though there is a high level of consistency in the child trees of a snow apple.

I think, if you can get the weight stress on the tree down, and encourage the shoots you show, you might be able to keep this tree going for your lifetime or more. Grafting a shoot onto a new tree in your yard would also be a good measure just in case.

You couldn't graft anything onto the inside of the hollow. I just think, with vigorous young growth from low on the trunk, you could probably develop that into a decent tree if the existing trunks fail.

There are plenty of hollow trees all around the world that have survived for centuries.  The living part of the trunk is the thin layer just below the bark...as long as that is preserved intact you're good.  The challenge is to keep the trunk from breaking (in a storm or under a heavy load of fruit or ice) or rotting.  Seeing that there is a clear channel for rainwater to drain out is essential to the second goal, as well as possibly painting or otherwise treating the exposed wood in the hollow.  You might be able to tie or cable the top branches of the tree to each other for stability, and plant other things nearby as windbreaks.  To be broken down at last in a storm or by decay are the main end fates.

Thanks Glenn,

I should look for young growth at ground-level and encourage that, at least one new trunk on either side of the hollow one. Just in case.

Alder, that you very much for the encouraging fact that a hollow tree can live for many years. I will be pruning the tree down to a minimal weight. The idea of tying cables across the top is a fun idea, I'll explore the possibilities there as well. Protecting the indea from rainwater is a great idea. I might drill a small hole and line it with plastic or metal, and put some sort of funnel inside. Maybe just some sort of non-sealing cover would be better though. The tree is right next to a dense cedar hedge as a windbreak, so we're all set there.

With any luck and with the advice I've gotten thus far, I hope tree still has decades left in it. :)

I've heard stories of people putting swarms of honeybees into suitable hollows to heal trees (and help bees). You might have to modify it (like put a cover over the top to keep rain out, which can be as simple as a piece of wood nailed to the tree) but it could work. I heard a story from an old timer of a tree that had a hollow. Bees create an environment that is said to heal trees. A lot of their propolis and wax is said to be anti fungal and anti microbial. Anyway, eventually the hollow in the tree sealed after the last colony moved out. You could give it a shot

James, that's a really interesting concept that I hadn't thought about! I'm not sure it's directly applicable however, since we love sitting directly under that tree and have a two year old daughter who enjoys her time there as well. We might be a little too close for comfort and I'd hate for the bees to get defensive when a young child starts poking at them. :)

Just looking for information on teh subject, I have a bunch of apple and plum trees which are hollow (>> 100 years old, I live in Scotland, the house was built sometime around 1700) ) and they seem to be doing fine. There was one tree which was particularly bad. What I did was put a wire brush on a drill and got rid of all the soft moisture retaining wood. Then vacuumed our all the dust. Essentially just keep it clean.  The good wood that's left seems to go as hard as steel and the rot stops. Other than that I just keep them pruned so the wind is not to hard on them. And most importantly learn to love the imperfections.

One of the best things to do it put props on the branches, simply legs to take the weight of those big and spread out branches and stop them tearing the weakened trunk apart.

A good old Dorset friend of mine told me to put newspaper into the hollow of the Appletree and then set fire to it. He might well have got this information from his father and his grandfather who knew countryside folklore extremely well. We did this about 25 years ago and the tree thrived producing many apples. It was totally hollow on the inside and only appeared to be supported by the bark and a little of the tree. We have a video of this somewhere. Today, I repeated the same thing to another old very hollow-trunked Appletree.  I now look forward to seeing if it will produce good food in the summer, and hope it has ‘long life and happiness’! I have taken a video of this also.

Very interesting idea! I love the thought that this is a traditional practice. I imagine the scorched interior is stronger after this treatment.