Magnolia in decline

[rumination]

I am hoping that I can get some good advice here. In the garden I work at there is a Magnolia grandiflora that appears to be struggling, and I have not been able to figure out what the problem is. The tree is about twenty years old, twenty feet tall, 10" DBH. For the past few months the foliage at the top of the tree has been yellowing and thinning out. Until recently, I was not able to identify any insect pests at all on the tree. In the past week several of the small lower branches have been attacked by twig borers, but this may be due to the overall low vigor of the tree. The tree is growing in acidic, well drained soil, in a high rainfall area. Soil organic matter is relatively low, as is typical of the moist tropics. I have not yet done a root excavation, however all surface roots appear to healthy, and there are no above ground signs of girdling roots (i.e. flat surfaces on the lower trunk). The tree is currently flowering, and I was planning on waiting until this was done to see how much of a growth spurt it put on before I considered a root inspection.

We would very much like to save this tree. It is an 'Andrew Jackson' cultivar, and is a cutting from the tree at the White House. If any of the arborists from the southern states have any experience with magnolias, or if anyone can give me advice on my diagnostic process, I would very much appreciate it. Thanks.

I'll try to post some pictures.

 

[Treeman14]

It sounds as if you have already found the problem, even if you didn't recognize it. The girdling roots would cause the symptoms you have described. Its a fairly common problem on young magnolias here in Florida.
Do the root inspection and correct the girdlers as soon as possible.

 

[rumination]

Whoops! I left out an important word there. I better edit that to read "there are NO above ground signs of girdling roots".

 

[Dadatwins]

Agree with the girdling roots on this one. Hard to tell on magnolia for a visible above ground sign, but I would suspect below ground is where the problem lies. Lets hope it was planted properly and and you do not find a wire basket entombed mass of roots below the surface. Good luck.

 

[treeseer]

The tree is currently flowering, and I was planning on waiting until this was done to see how much of a growth spurt it put on before I considered a root inspection.

No reason to wait, as Brett pointed out

We would very much like to save this tree. It is an 'Andrew Jackson' cultivar,

Other seedlings from the F&H Nursery had girdling issues.

I'll try to post some pictures.

Good! I'd love to see part of the Lyon again.

The magnolia that was the subject of the dendro detective article in the april arborist news (o and thanks for mailing that wcisa mag) had few aboveground signs of girdling, but massive belowground issues.

 

[rumination]

Thanks for the advice guys. Sounds like my suspicion that the root cause (pun intended) of the problem lies underground may be reasonable. I will go ahead with the root inspection sometime this week.

I still haven't received the April arborist news. Look forward to seeing it.

I'll post a few pictures sometime soon.

 

[rumination]

Okay, here's a couple of pictures.


Here's the thinning top.

 

[rumination]

Here's some of the branches that the twig borers got. I'm pretty certain that they are unrelated to the trees problem, though.

 

[rumination]

Whoops again. I think I got my photos mixed up. Anyway, you get the picture (pun again!).


Here's one for treeseer.

 

[treeseer]

Thanks for the rainbow; that is one pretty piece of Paradise.

Compare you rpic of the thinning top to the one heading up the article; similar symptoms, yes.

Someone needs to kick your mailman's aspirations; long time crossing that puddle. The issue had an overall theme of roots so it shoul dbe of help; it'll be verrrry interesting to see what it looks like down there.

 

[clearance]

Saw it down............................................. just joking Treeseer

 

[treeseer]

Saw it down............................................. just joking Treeseer

Just try it, you wild whacker, and Andy Jackson's ghost will take care of you like the real AndyJ did the Brits at the Battle of New Orleans.

Rumi, Mike Dirr lista M grandi as zone 6- 9(10). Where are yo, zone 150?

 

[rumination]

Treeseer, despite our outrageous zone number, magnolia do grow well here, although they do not get as large as they do on the mainland. The largest one I have seen in Hawaii was only about 35 feet tall. And to be technically precise, I think we are in zone 11 over here.

Anyways, did a root excavation today. This was quite definitely a potbound tree. Underneath the root crown I found a tangled mess of swollen roots. One buttress root plunges straight down to unkown regions. It's not pretty. On the other hand, the tree also has several good sized healthy buttress roots that are free of the tangled mess. I only found a couple of small girdling roots, which I pruned. I'm not really sure how to deal with the massive tangle of swollen roots. They are so tight together that it may be too late to do anything about it.

I am not willing to make a diagnosis yet because it turns out that verticillium wilt may be a second factor here. The tree is showing most of the symptoms that this fungus produces, and there is a history of other trees planted in the same area dying slow mysterious deaths. I'm going to take a tissue sample, and maybe even a soil sample, down to the university for testing.

To be safe we will be taking cuttings and collecting seed from this flowering so that the tree can be properly propagated and planted into a healthy area.

 

[treeseer]

"] I'm not really sure how to deal with the massive tangle of swollen roots. They are so tight together that it may be too late to do anything about it."

Sad but often true.

"I am not willing to make a diagnosis yet because it turns out that verticillium wilt may be a second factor here. ... I'm going to take a tissue sample, and maybe even a soil sample, down to the university for testing."

Good idea, but with all due respect to state labs, you may want to check it yourself too. The damage to sapwood is distinctive and fairly easy to read.
Remember too that vert has a chronic phase, and trees can codit.

"To be safe we will be taking cuttings and collecting seed from this flowering so that the tree can be properly propagated and planted into a healthy area."

Smart move. I'd also let the supplier know that they sold you a defective tree; not so much to get a refund (most of their operation was wiped out in a hurricane), but to get them to grow better trees for the future. Sending them a picture of the roots (and posting one here?) may help.