Albizia saman – Rain Tree leaves started yellowing

[mike020]

Hi,
I’m looking for advice from people who have experience growing tropical trees.

While on vacation in Thailand, I came across a tree that I really liked (most likely Albizia saman – Rain Tree). I decided to collect a few seeds and try to grow it at home (Ilive in holland), with some help from ChatGPT.
I planted the seed in June using Pokon Bio Palmen Potgrond Turfvrij. As of today, the tree is about 150 cm tall, growing in a large self-watering pot (approx. 20 L). I’m using a Spider Farmer SF2000 Pro grow light at about 20% power. Room temperature is 22C to 28C Until recently, the plant was growing very well, but over the past few weeks some problems have appeared.

Symptoms:​

• leaves started yellowing (first the lower ones, then gradually higher),
• some leaves dry out from the edges, others fall off completely,
• some leaves have lighter spots or short streaks, sometimes slightly raised and noticeable to the touch,
• some leaves feel wrinkled, while others are completely smooth,
• when one leaf on a branch starts to yellow, often more leaves from the same branch fall later.

Soil / watering:​

• previously watered with tap water (quite hard); for the past few days I’ve been using filtered water / rainwater,
• Pokon fertilizers were used (fertilizer spikes + liquid bonsai fertilizer), but only occasionally,
• fungus gnats appeared – I treated the soil with beneficial nematodes (BTI / nematodes against larvae).

Additional info:​

• I need to cut the top of the tree (it’s too tall and is touching the ceiling). One of the photos shows where I’m holding the stem – that’s where the main shoot was cut before. As you can see, two new main shoots appeared in its place.
• I’m planning to try rooting the cut top to grow a new plant.

My questions:​

1. Do these symptoms point more toward salt buildup / root stress, or rather leaf diseases or pests?
2. Is it normal for Albizia to drop entire groups of leaves when stressed?
3. After conditions stabilize, will leaves regrow on the same branches, or only as new growth?
4. What should I pay special attention to when continuing to grow this tree indoors?

I’d really appreciate any advice, especially from people who have experience with Albizia or other tropical trees

 

[Orion_metalhead]

Fungus gnats are indicative of overwatering.

Show pictures of soil. How often are you watering?

 

[mike020]

Depends . I always check with my fingers. If top 10cm is dry, then I add water

 

[Orion_metalhead]

Yeah, but such an organic mix will hold a lot of moisture in the bottom 1/2 of the container. this is why we usually use inorganjcs in bonsai - it better regulates water levels in a container.

How deep is the pot?

 

[mike020]

its a VÅRDTRÄD self-watering plant pot (https://www.ikea.com/us/en/p/vardtr...door-outdoor-transparent-anthracite-90570864/)

​

 

[Orion_metalhead]

Those type of pots are going to cause a ton of problems for a bonsai in heavily organic soil. In that type of pot, you are better off using a long wooden dowel and pushing it to the very bottom of the pot and leaving it there. You then periodically remove the dowel and feel how wet it is. You want it to be just slightly moist. Anything else and you are running the risk of an anaerobic environment and root rot. We use completely free draining pots for our trees for this reason. My gut is the soil is sopping wet at the bottom of the pot.

 

[mike020]

So in my case, I should replace the pod + new dry soil.

Or I could modify my current pot by drying extra holes?

 

[Kievnstavick]

I can't tell in the photos, but are the yellowing leaves near the bottom of the tree? I also think you are misidentifing some parts of the tree. Ablizia Saman have pinnate compound leaves. In the image below, this is one leaf. When analyzing the health, you should look at the leaf as a whole rather then the individual leaflets. When you take a quick look at the tree armed with that information, you only have a few number of branches.



Some food for thought: A 6 month sapling in a 20L pot is vastly over potted. A smaller pot will perform a lot better in terms of watering. For reference, i (and the nursery trade) would keep a sapling in a 3.5L pot for approximately a year before increasing to a 7L pot. A planting pot is not like the garden bed outside. More soil in a planting pot does not mean more growth.

I would agree that overwatering maybe an issue. In my opinion, I would only use self watering pots/devices on plants that love to sit in water. Albizia saman is not one of these species. They like moist substrate but not saturated. A self watering pot with potting soil is a saturated mix.

I would add that the this tree seems to be suffering from a nutrient deficiency. From your description and the image, it sounds like a magnesium deficiency. Make sure your fertilizer is supplying all the macro and micro nutrients are being supplied and make sure you follow the directions. Also, keep in mind that any fertilizer runoff/discharge is getting put back into the soil. So there is a possibility that you are having a salt build up which can look like a general deficiency, but in reality the ph and salinity inhibits plant uptake rather then it being missing.

Also, are you sure this is an Ablizia Saman? The leaf shape roughly looks right but the size is vastly different then the ones I found all over Hawaii. The leafe was about the size of a hand and the leaflet being the size of a thumb at the largest. On yours, the leaflet looks to be the size of two or three fingers combined.

Now that leads into my next comment: the trunk on that tree seems way too narrow for the height of that tree. My trees at 60cm had the trunk thickness of yours currently. The fact there is a stake and some wire as well make me think the tree is having issues supporting its own weight. A. Samen are rapid growers, but they are not 150cm in 6 months quick while in a pot.

To sum up that last paragraph, your tree is desperately asking for more light. The extra large leaves and leggy growth are signs it is starving for light. Your yellowing leaves can also be attributed to this as the tree is dropping the resource-draining leaves in favor of the resource producing leaves. This can also look like a nutrient deficiency as the plant is pulling its resources from the leaf in preparation to drop it. I expect hat only your top nine leaves are productive (the ones above the 2nd wooden cross support). The growling set to 20% power sounds very low to me.

For instance, in the image shown of my growing shelf this grow light is set to 100% power. (This is a picture at the begining of fall. The folliage density is much higher now.) I only had issues with leaves burning once they were within 3cm of the light. One thing to keep in mind is that light produced from a grow light drops of dramatically



For comparsion here are some of my A. Saman in their second year repotted twice at this point but allowed to grow freely during the summer. So there was some growth inhibiting, but not a lot. They were bare rooted, root pruned, and placed back into a 3.5L pot as their root systems were not developed enough for a 7L pot. Notice how much more leaves are in a smaller space. In my observation, A. Saman are decently dense tree in terms of foliage mass.



All in all, I think the biggest issue you have right now is light. If you increase the light availability (this will involve a lot more then increasing the power of your grow light) then the tree will use more water. Using more water should hopefully reduce the overwatering aspect

 

[mike020]

I took the tree out of the pot. The soil at the very bottom was not extremely wet, but when I took it in my hand and squeezed it, I was able to press out some water.

I have ordered a new pot, and in the meantime I transferred the tree into fresh soil. I hope it will survive.