Why do healthy branches simply die back?

[Clicio]

It's a genuine question.
I have two Calliandras that are very healthy, growing like crazy in our tropical springtime, but one or two old, well ramified branches jut stop leaf production and dry from the tips to the inside of the tree.
Sorry, no pictures yet, but any considerations will be welcome.
;-)

 

[peterbone]

There are multiple reasons. Some I can think of are:

- Branches die off from lack of light. Perhaps those branches are shaded out by other branches. Pruning outer growth mid season can help reduce it happening. Turning the tree regularly can also help.

- Bar branches can often cause one to become weaker as the flow of energy prefers one over the other. One may die back.

- Something damages the branch. Perhaps an insect or fungus attacks it or it's damaged while wiring. Wiring in winter can cause die back as frost enters small cracks in the bark.

- Weak roots can't supply the foliage mass with enough water, so some branches are sacrificed for the survival of the tree.

I'm sure there are many other possible reasons.

 

[Stan Kengai]

Some type of blight?

 

[Clicio]

- Bar branches can often cause one to become weaker as the flow of energy prefers one over the other. One may die back.

Could be. I hadn't thought this could happen, but makes sense.

- Something damages the branch. Perhaps an insect or fungus attacks.

This possibility needs close inspection, I guess. Thanks.

- Weak roots can't supply the foliage mass with enough water, so some branches are sacrificed for the survival of the tree.

Hummm... I didn't repot them this spring (here) as I could see no signs of root bound or lack of good drainage, but weak roots would not make the trees thrive, right?
Thanks for the useful response!

 

[Wires_Guy_wires]

I can relate to the 'energy preferral' theory. Because usually when a part dies back, there's always a stronger part that starts growing a week or two in advance. I'm thinking tropicals by nature, act like pines: without manual balancing, it will start growing from one point up to outgrow all competition. Like what happens in the wild.
Cutting back runners does seem to save, or at least preserve, lower branches.

I also found that bending branches to end up lower than where they meet the trunk, is a death sentence for those branches. Every tropical I have is a broom or multi-trunk broom.. Because those are the parts that survive.

 

[River's Edge]

If there is nothing evident on the foliage or bark to indicate disease or insect damage, then i would suspect the roots. in some plants the root structure is specific to certain areas of the branch structure. damaged roots in one area of the root ball could affect a branch while remaining parts are healthy.
Root aphids can do a lot of damage without noticing much of a change in drainage or over compacted roots.
I would check the root ball particularily on the side that the branch died.

 

[sorce]

Could be. I hadn't thought this could happen, but makes sense.

Of bar branches...and general natural tree selection of what goes...

Someone brought it up on FB...how untouched trees end up under the "rules" naturally.
While man pruned trees die readily.

Its real.

S