Help with a recently yellowing Coast Live Oak

[MrBonsai19]

This is a look at the tree when I bought it in two months ago:



It looked about the same for a month or so, however in the past two weeks the leaves have started yellowing (from the tip of the leaf back toward the interior of the leaf) :



I live in Oakland, California and was told the tree had been repotted in Spring of this year. We recently had a week-straight of rain, so I am worried it might be over-watering related, but I was also under the impression that a quality Akadama/Pumice/Lava mix would be hard to over-water.

I would love any advice about

1 - should i possibly plan to up-pot this tree into a larger container to help it recover its vigor?
2 - is there anything worth doing in response to these brown/yellowing/dying leaves?

This is the first real bonsai tree I have purchased and I am a bit desperate to see it through to vigor and health.

 

[Shibui]

I try not to panic at just a few yellow leaves. Sometimes that happens.
A week of rain is not enough to cause root rot/overwatering. That takes months to get started so unless you were already overwatering before the rain that's not your problem. Ad, yes, APL mix is used because it is difficult to overwater.
My experience is that oaks don't like root work and can take a long time to recover from a severe root reduction. I've had some that grew very poorly for 2 years after a severe root reduction. What you are seeing now may be a reaction to the spring repot. Much depends on how much root reduction was done and how much soil was changed over at that time.

I would resist repotting or up potting or any other interfering with the roots unless you can pin the problem down to the roots. The tree has already suffered stress. In my view, repotting will only add to that.
The only thing I know to do is continue good care. Definitely don't let it dry out because you are frightened of overwatering. In drier climates like ours, underwatering kills far more trees than overwatering.
I think it's a pity you did not choose a more resilient species for your first 'real' bonsai but it is what it is. Good luck.

 

[MrBonsai19]

I try not to panic at just a few yellow leaves. Sometimes that happens.
A week of rain is not enough to cause root rot/overwatering. That takes months to get started so unless you were already overwatering before the rain that's not your problem. Ad, yes, APL mix is used because it is difficult to overwater.
My experience is that oaks don't like root work and can take a long time to recover from a severe root reduction. I've had some that grew very poorly for 2 years after a severe root reduction. What you are seeing now may be a reaction to the spring repot. Much depends on how much root reduction was done and how much soil was changed over at that time.

I would resist repotting or up potting or any other interfering with the roots unless you can pin the problem down to the roots. The tree has already suffered stress. In my view, repotting will only add to that.
The only thing I know to do is continue good care. Definitely don't let it dry out because you are frightened of overwatering. In drier climates like ours, underwatering kills far more trees than overwatering.
I think it's a pity you did not choose a more resilient species for your first 'real' bonsai but it is what it is. Good luck.

Appreciate the feedback. Since October i have been watering when the top-most layer of akadama looks light/dry visually. I have struggled to use the "feel" method with akadama compared to organic soils where it's so much easier to feel the moisture in the top layer. For this tree whenever the akadama on top looks dried out is when I water; for most of the Fall season that has been either daily or every other day. I was starting to consider that maybe this was too much, and then pile on the 5 straight days of rain and perhaps the situation compounded. But I am really not sure if this is this issue or not.

If I did up-pot it, the goal would be to do so with minimal root disturbance, and I would do so in late February (not now) however I know there's a fair difference between minimal and none, so I will hold off on doing anything until we can start to see some vigor and growth. Hopefully as you suggested it will just be a matter of maintaining good care moving forward and letting the tree bounce back in Spring. Thank you very much for giving in-depth advice here!

I am curious about your suggestion that Coast Live Oaks are not resilient. They grow pretty easily around this area at least in terms of the small ones that are constantly shooting up in the yard, and it is a native species. Is your experience that Coast Live Oaks are not strong/vigorous growers or more so that they struggle with pest/fungus/disease frequently? Just curious about that last part of your comment. I have been doing some research on CLO common struggles and Sudden Oak Death kinda terrified me as well; one of the local oak growers applies a systemic treatment to proactively guard against Sudden Oak Death and I was considering using one of the recommended products for this (Phyton 27). But I have not gone forward with that yet as it seemed like a harsh chemical to apply and I was not sure whether the prior owner of the tree had already applied a systemic this year since I didn't know enough to ask about that at the time when I purchased it. Seeing the recent issues I have started to reconsider, but at the same time it obviously does not seem like an ideal time to be putting fungicide into the tree.

 

[BrianBay9]

Sometimes they just decide to drop a limb for no apparent reason. It's happened with one of my CLO that has been in a pot for years, doing really well. Dropped one major branch and since then the rest have been thriving. I had to restyle a bit but it's still one of my best oaks.

 

[WinstonWolfe]

I'll second what Shibui stated.

Something else to keep in mind as you venture into the bonsai hobby:
As a general rule when purchasing a tree. It's safer to buy something that it has lived in its current pot for at least one full year.
If it were too aggressively pruned to fit it into the pot, that might not show until much later.

Good luck

 

[namnhi]

Sometimes they just decide to drop a limb for no apparent reason. It's happened with one of my CLO that has been in a pot for years, doing really well. Dropped one major branch and since then the rest have been thriving. I had to restyle a bit but it's still one of my best oaks.

I have had this happened to my cork oaks. Oaks seem to readily drop a limb for no reason.

The tree posted doesn't look very healthy. I can see many branches are dead but there are plenty of live branches as well. I would just wait and see and make sure the tree does not stay too wet or too dry.

 

[Wulfskaar]

CLO is an evergreen tree, but it does need to get rid of old leaves at some point. Hopefully it's just doing that now.

The huge one in my yard is very healthy, but drops old leaves all the time.

 

[Shibui]

I am curious about your suggestion that Coast Live Oaks are not resilient.

I don't think I mentioned Live oak as not resilient. If you interpreted what I said as that my apologies. I did say that oaks (generally) don't cope well with severe root pruning. The fact they grow like weeds in the ground does not stop them resenting root interference. In bonsai terms, resilience means able to grow again after pruning, root pruning and occasional watering irregularities. Trident maples, Chinese elms and many Ficus sp are resilient in bonsai terms, oaks less so.

 

[MrBonsai19]

Hey All just revisiting this thread as I fear the tree continues to show signs of declining health. I am worried about possible pathogens/bacterial/fungal infections in the root system. Although I do understand the repotting in the previous Spring could be a factor, something about this steady decline of health which began in late November and has been steadily progressing further suggests to me there is something I am doing wrong or something affecting this trees health besides the repot.








I tried to do the tap and smear paper method for testing the presence of spider mites, but from what I could tell that is not the issue. I have inspected the foliage very closely and I cannot find any sign of visible pests. I have dug back the top layer of soil in the container and similarly cannot see any obvious signs of root pests either.

As the tree is not doing well I am sure that makes it an easy target for compounding stressors. I don't know if maybe that is what is happening is that the repot was the onset of poor health, and now additional stressors are acting on the tree. I am considering applying a systemic bacerticide and fungicide called Phyton 27 which was recommended to me by another member of my area that grows a lot of Oaks: https://www.amazon.com/Phyton-Oz-Sy...d=1736355930&sprefix=phyton+27,aps,148&sr=8-1

This is the time of year to apply systemics I think and it is something I wanted to do independent of the current health issues. This is from what I understand the best preventive for Sudden Oak Death which is a somewhat significant issue in the region. But of course I am hesitant to take any severe interventions at this point without some more experienced perspectives.

Any feedback is most welcome. Thanks

 

[Desert O'Piñon]

There are many here who are more knowledgeable, but these closeup shots look like powdery mildew to me. I'm not very familiar with Oakland weather, but I'm pretty sure it's usually pretty humid? Humidity in a warm or temperate climate presents favorable conditions for fungal bodies to flourish and populate. If I'm not mistaken, your systemic will likely be the solution, assuming the product is labeled for powdery mildew (according to the link, it is), and assuming my amateur diagnosis is correct.

 

[BrianBay9]

Sudden oak death would be moving much faster than this. Remove the affected leaves or small branches and spray with a topical fungicide like copper. Most folks I know in the bay area spray with fungicide three times during with winter - around Thanksgiving, around New Year and around again around Valentines Day. Check out John Thompson's advice where you can find it, like the Midori newsletter. He's the most experienced guy I know about coast live oaks. https://www.midoribonsai.org/news/2020-december-tree-trips

 

[yenling83]

Hey Mr. Bonsai, I'd recommend the following:

• Full Sun-
  • Coast live oaks seem to do best for me in full sun. How much direct sunlight does it get through out the day? You want to find the spot in your yard that get's the most sun throughout the day and put it there. They can handle even more direct sun than Junipers
• Water more frequently-
  • I generally water my oaks a bit more frequently than other trees in my garden. If the top soil Akadama is turning from dark to light, then the tree is too dry. Coast live oaks like lots of water. I'd also top dress with a little shredded Sphagnum moss or S moss/live moss.
• Larger Container-
  • A larger container or possibly grow box will help increase the vigor of that tree. You can always go back to a smaller container in the future.
• Ensure Oxygen/water can easily penetrate root ball
  • Coast live oaks are notorious for creating a root ball like cement. Personally I repot mine on a yearly basis to ensure air/water can penetrate the root ball. I'd go light on the repotting-not cutting too much. But try to comb out the roots and work any hard areas of the root ball that will not allow water to penetrate.
• Spray
  • I'd spray with Fungicide and insecticide
• Don't touch it for the next year
  • Other than cutting away dead branches and removing dead leaves. You just want it to start growing strongly for the next year, then re-evaluate after that. You won't see any improvements until it starts growing in spring.

Best of luck!

 

[MrBonsai19]

Thanks for the feedback @yenling83 @BrianBay9 @Desert O'Piñon !

 

[MrBonsai19]

Hey Mr. Bonsai, I'd recommend the following:

• Full Sun-
  • Coast live oaks seem to do best for me in full sun. How much direct sunlight does it get through out the day? You want to find the spot in your yard that get's the most sun throughout the day and put it there. They can handle even more direct sun than Junipers
• Water more frequently-
  • I generally water my oaks a bit more frequently than other trees in my garden. If the top soil Akadama is turning from dark to light, then the tree is too dry. Coast live oaks like lots of water. I'd also top dress with a little shredded Sphagnum moss or S moss/live moss.
• Larger Container-
  • A larger container or possibly grow box will help increase the vigor of that tree. You can always go back to a smaller container in the future.
• Ensure Oxygen/water can easily penetrate root ball
  • Coast live oaks are notorious for creating a root ball like cement. Personally I repot mine on a yearly basis to ensure air/water can penetrate the root ball. I'd go light on the repotting-not cutting too much. But try to comb out the roots and work any hard areas of the root ball that will not allow water to penetrate.
• Spray
  • I'd spray with Fungicide and insecticide
• Don't touch it for the next year
  • Other than cutting away dead branches and removing dead leaves. You just want it to start growing strongly for the next year, then re-evaluate after that. You won't see any improvements until it starts growing in spring.

Best of luck!

I’m gonna go ahead and up-pot to a grow box. Not going to do any root work just give it more space. The current soil mix is 1:1:1 APL. My plan is to tease away as much of that APL mix as possible without damaging or removing any roots and then replace with pure large size (1/4”) pumice.

Some questions I am feeling unsure of:

-Would it be better to refrain from removing any of the existing soil to minimize stress as much as possible?
-if leaving all the existing soil is better than gently teasing away that existing soil, then would the grow box medium be better off matching the current 1:1:1 mix to avoid different water holding rates across the grow box laterally? Or would surrounding the existing 1:1:1 mix with pure pumice be OK?
-does the size of the grow box matter? I know for yamadori the goal is to keep the grow box very compact relative to the root spread but this is a little different as this tree hopefully has a lot roots to begin with… so it would hopefully be Ok to move to a larger container size for the goal of increasing its health?


Here is the frame I have for the grow box it’s 1”x8” untreated redwood. The current ceramic container is 16”x12” interior dimensions and the grow box is about 3 inches larger roughly 19”x15” ID

 

[yenling83]

I’m gonna go ahead and up-pot to a grow box. Not going to do any root work just give it more space. The current soil mix is 1:1:1 APL. My plan is to tease away as much of that APL mix as possible without damaging or removing any roots and then replace with pure large size (1/4”) pumice.

Some questions I am feeling unsure of:

-Would it be better to refrain from removing any of the existing soil to minimize stress as much as possible?
-if leaving all the existing soil is better than gently teasing away that existing soil, then would the grow box medium be better off matching the current 1:1:1 mix to avoid different water holding rates across the grow box laterally? Or would surrounding the existing 1:1:1 mix with pure pumice be OK?
-does the size of the grow box matter? I know for yamadori the goal is to keep the grow box very compact relative to the root spread but this is a little different as this tree hopefully has a lot roots to begin with… so it would hopefully be Ok to move to a larger container size for the goal of increasing its health?


Here is the frame I have for the grow box it’s 1”x8” untreated redwood. The current ceramic container is 16”x12” interior dimensions and the grow box is about 3 inches larger roughly 19”x15” ID

-Would it be better to refrain from removing any of the existing soil to minimize stress as much as possible?
I would remove the tree from it's current pot and use a chop stick, or root hook to gently comb the roots out. I might actually water the tree once you've taken the tree out to see how the water penetrates the root ball. Coast live oaks are notorious for creating dense areas in the root mass which don't allow water to penetrate. I would comb the roots out gently and give them a very light cut back with sharp scissors. I generally haven't had the best results slip potting trees and feel they start growing better if you comb out and trim the roots. Also, you want to determine if water is able to penetrate the root ball. if you don't work the roots a bit, this will further exacerbate the water penetration problem over time.



-does the size of the grow box matter? I know for yamadori the goal is to keep the grow box very compact relative to the root spread but this is a little different as this tree hopefully has a lot roots to begin with… so it would hopefully be Ok to move to a larger container size for the goal of increasing its health?

I think that box looks like a pretty good size. I do agree with Ryan/Randy regarding a nice tight box for collected yamadori. However, with broadleaf trees you should go a bit bigger IMO and consider the rainfall that Ryan and Randy get. Their trees stay too wet, which is generally not the case in CA. With broadleaf trees, from my experience a bigger box(up to a point) makes them grow stronger/faster. I'd also put the box on the ground as opposed to on a bench.

 

[MrBonsai19]

-Would it be better to refrain from removing any of the existing soil to minimize stress as much as possible?
I would remove the tree from it's current pot and use a chop stick, or root hook to gently comb the roots out. I might actually water the tree once you've taken the tree out to see how the water penetrates the root ball. Coast live oaks are notorious for creating dense areas in the root mass which don't allow water to penetrate. I would comb the roots out gently and give them a very light cut back with sharp scissors. I generally haven't had the best results slip potting trees and feel they start growing better if you comb out and trim the roots. Also, you want to determine if water is able to penetrate the root ball. if you don't work the roots a bit, this will further exacerbate the water penetration problem over time.



-does the size of the grow box matter? I know for yamadori the goal is to keep the grow box very compact relative to the root spread but this is a little different as this tree hopefully has a lot roots to begin with… so it would hopefully be Ok to move to a larger container size for the goal of increasing its health?

I think that box looks like a pretty good size. I do agree with Ryan/Randy regarding a nice tight box for collected yamadori. However, with broadleaf trees you should go a bit bigger IMO and consider the rainfall that Ryan and Randy get. Their trees stay too wet, which is generally not the case in CA. With broadleaf trees, from my experience a bigger box(up to a point) makes them grow stronger/faster. I'd also put the box on the ground as opposed to on a bench.

Thanks so much for the feedback! I like the idea of just lightly trimming the roots to stimulate them… I applied the systemic fungicide /bactericide Phyton 27 twice over a 10 day period in late January and lime sulfur earlier in January. I can only hope that has covered the threats from pest and disease. The tree seemed fine with those treatments no major change either way. And then the up-pot to a pumice based mix in a larger container further improves its ability to recover this coming season. I haven’t removed any branches yet I’ll probably cut back anything that looks dead if/when the spring flush gives me a better sense of what is still moving sap.

 

[MrBonsai19]

Just adding an update here to share my progress. I had been assuming there was some kind of pathological issue affecting my tree as folks can see just by reading the previous posts. However, spending more time reading about fungus like anthracnose the part that did not really make sense to me is that this fungus is relatively dormant in winter and it is most active in Spring and Summer. However, my oak tree seemed to really decline toward late fall and continue it's significant leaf drop and twig dieback throughout the winter season.

So I was feeling less convinced about that diagnosis. I did apply the broad spectrum fungicide and bactericide Phyton-27 in late January (two applications ~10 days apart) as well as a Lime Sulfur dormant spray in early January (25:1 dilution relatively strong). Neither of those applications really seemed to have a significant impact on the die back which continues to this day. The yellowing and dropping of leaves has been a fairly constant progression throughout the entirety of winter.

I spoke with another very experienced professional about my tree and he suggested it was likely the cumulative stress of suboptimal care, suboptimal growing conditions, repotting and a transition to a new environment over the course of 2024 which was leading the tree to abandon its weakest growth areas. From what he could see of my pictures the die back and leaf-drop was much less pronounced in the tips and it seems like the tree has buds set for the coming year which are still active. So his guess is that the tree was just trying very hard to balance energy and abandoning everything that may be old, weak, or afflicted by other issues as a result of the tree being weak and unable to put up a strong resistance overall.

He suggested that the tree probably did not *need* to be repotted and most likely would have a weakened flush this growing season but with quality care and growing conditions, the buds that would be set during the course of the 2025 growing season would contribute to what would hopefully be a step toward full recovery and by the 2026 growing season we may see the tree shifting to be much healthier, stronger and not suffer from the die back of old growth anymore.

However he said repotting the tree into a grow box would help over the long-term and so although it was not necessary it would be a fine step to take based on my own personal goals. If I was OK with a much longer timeline for this tree, knowing that going into a growbox would likely set back the ability to get this tree into a bonsai container as it would grow coarser roots and coarser foliage but it would help the tree become more vigorous over the coarse of 2-3 growing seasons, that it would be up to me if I wanted to do that.

And so I did decide in the end to take that step. I really wanted to make sure the quality of the soil was not a huge issue or limiting factor and because I could not really see what the soil was like below the surface it was just an area of doubt and uncertainty for me that I felt much better about knowing exactly what the roots and the soil looked like over the coming years. And I was also more inclined to set the tree up for maximum health and vigor and knowing that most likely multiple areas of branching and structure need to be re-developed.


Starting off:


For the most part the root ball looked good except for this one area where there were a lot of dead roots. This is the only area where I did end up performing some root work to clear out the dead roots. This is the one area where I found a lot of very dense organic soil. The soil was dramatically different in this one area compared to the rest of the tree and it took me a while to tease away as much as I could. In the end I didn't even remove the entire pocket of dense organic soil but I did not want to be more aggressive and decided to stop after clearing away what I felt like was a decent portion of the problem soil:








I realize this operation is a setback for the tree and it will now need to use more energy to re-establish itself in the new container, so there will likely be less growth this season as a result. However my hope is that over a 3 year horizon this will enable the tree to become much healthier than the previous container, and hopefully clearing out the overly compacted soil in that on area below the front will help the tree establish more growth as well. It also gives me significantly more peace of mind to know that the root ball is relatively stable aside from that one section and there aren't any significant issues below the soil that would lead to further decline or some kind of emergency operation outside of the repotting window. As much as I would like to take @yenling83's suggestion to put the box on the ground I don't have a space that would allow me to safely do that so for now we have to keep it on this stand.