1

I don't if this is rot where several large branches meet. It is soft and dark colored matter, almost like compost. I was able to peel off a patch (see circled area in the first picture). Prompted by this, I poked into the lichen at a different branching point and underneath it I found the same black rot (2nd pic). A different location some weeds are even growing from such matter (3rd pic).

Should I be worried and is there anything I should do to mitigate the problem?

Tree 1 large Tree 2 large Tree 3 large

2

Your tree is decaying, and you can not stop it. If you leave it alone, the decay will progress next several years, trunk will probably split at some point in time, and the tree will eventually die (soon in the scale of tree or human lifetime). Weed growing from the tree does not affect this process in a significant way, you can leave it or remove it as you wish.

You can do something though, here are alternatives:

  1. Prune the tree by cutting 30% of foliage every autumn or winter, so that the physical pressure on decaying trunk decreases. This may prolong the life of the tree significantly.

  2. Cut everything higher than 1m or 2m - this will likely kill the tree - and use the remaining snag as a home for insects, smaller mammals, etc.

  3. Same as 2), but also make (out of the tree remains) natural containers for ornamentals. This way you will have a nice conversational piece in your garden.

  4. Cut the tree completely.

4
  • That's sad to hear.. but thanks for explaining what's going on. The trees still flowered beautifully this past Spring. Do you know how many years did it roughly take for tree decay to develop into what you see in the pictures? I'm curious how long we have been oblivious to this.
    – P. B.
    May 28 at 12:39
  • The main problem here is the branching of the trunk. You have a couple of so-called "codominant" branchings that in turn created the problem of "included bark", and than this created rotting in these areas. (You can google these terms for more info.) All this started from the very young age of this tree, when it was only 3 or 5 years old. Tree expert guy go to the great length to avoid this kind of branching by forcing single, dominant, trunk. In summary, there was a problem almost from the beginning, and it just grew more serious over time.
    – Alex Alex
    May 28 at 13:57
  • @P.B. Trees usually rot from the inside out, but the living part of the tree is just under the bark so the disease has no obvious effect. Often the first sign of trouble is when something breaks in a storm, or when the disease reaches the surface. It may have been slowly developing for decades.
    – alephzero
    May 28 at 14:43
  • I'm relieved slightly that it's not something we might have done that led to the tree decay. And yes, I googled and learned quite a bit based on the information here. I didn't know pruning was not just for the looks.
    – P. B.
    May 28 at 15:13

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