Chinese Elm leaves turning yellow

[MRB]

Hello!

I am completely new to the Bonsai world and got my first tree, one month ago. It is a Chinese Elm. It was doing great during last month with good and fast growth but it is a few days and I am seeing many yellowing leaves. The tree is kept indoor on a window shelf, receives sunlight from 9 am to 2 pm, is watered every other day, and fed weekly with liquid fertilizer.

Along with yellowing leaves, I have also noticed some leaves that have not grown well with some pattern that looks like small holes. (Image 5)

I keep the Elm close to two other plants (Ficus Benjamina, and Ficus Retusa Bonsai). Is it something that I should be worried about or it is just the plant's process to adapt to its new location? (Considering that one month since I received that plant has passed)

 

[SeanS]

Can you keep it outside? Elms prefer being outside

 

[MRB]

Unfortunately, I live in a flat and that window receives the most light. As I said I am new to bonsai and the reason I bought it is because these Elms are advertised as Indoor/Outdoor plants.
Do you think placing the tree on a shelf like the below image (on the outside of the window) would be enough for the tree?

 

[Shibui]

Unfortunately we see post after post from beginners who have been assured that Chinese elm will grow indoors. While it may be possible for real experts in some special conditions the experiences of many show indoors is not a good place for Chinese elms for the majority of us. Unfortunately, unscrupulous dealers seem to underestimate the difficulty in order to make more sales and many beginners get caught out. I'm beginning to wonder if Bonsai sellers are related to Used car sales people?
Having said that, yours is doing remarkably well so far.
The yellow leaves all appear to be the oldest and it is natural for some of the oldest leaves to die off. Not usually anything to worry about. Yellow leaves can also be an indication of changed conditions. If those older leaves were adapted to more sun they may now be not good at harvesting energy in the new light regime so the tree is scrapping them in favour of the newer, better adapted leaves. Again, nothing to really worry about. Just the tree adapting to new conditions. You may see a similar thing if the shade adapted leaves are suddenly exposed to more, stronger sun. If possible build up to full outside sun little by little over a few weeks.

What does worry me a little is the very wet soil. Watering according to a calendar (every second day) is not good. Roots that are constantly wet get infected and die. When that happens the top soon follows. Need to water according to soil moisture. Let the soil get almost dry before watering again. Frequency will depend on size of tree, size of pot, soil mix, air flow, temperature, time of year and more. At some times of the year the tree may need watering only once a week. Other times of year when the tree is growing well, humidity is low and temps higher it may need water every day, some bonsai need water twice a day. The only way to tell when is to check soil moisture. Not just the surface which can dry when the soil below is still too wet. dig a little to check or use a skewer/chopstick as a soil moisture probe.

The small holes in one leaf looks like some sort of pest damage. Probably a tiny caterpillar but indoor trees are subject to a range of pests and diseases that don't seem to bother outdoor plants quite as much. Personally I would not worry about 1 leaf with a few holes but if it gets worse or if that bothers you you should seek out some sort of pesticide to deal with the problem. Systemic insecticide is surest but not sure those are still available in UK. Pyrethrum is safer and should deal with most caterpillars but you may need to spray several times to get full coverage.
Leaf size can be an indication of changed conditions. The smaller ones are way back so whatever triggered that is now gone because newer leaves are bigger and healthy.

I've never used a stickon plant shelf. At least with your casement windows you will be able to reach the shelf outside. Provided it is large enough for the tree and the pot and strong enough to hold it long term it should work.
Note that outside conditions will be very different from indoors so watering regime will change.

 

[MRB]

Thanks for the in-depth explanation. I appreciate it.

Regarding watering, I have 4 plants in total, and water them based on their soil condition but this Elm gets dry fast. I've purchased a soil moisture meter and water my plants based on the reported moisture level by the tool. I hope it is an accurate device but in general, I've heard more about overwatering problems than underwatering so I try to be a little ungenerous about watering until I gain more experience.

 

[dhelix33]

Unfortunately we see post after post from beginners who have been assured that Chinese elm will grow indoors. While it may be possible for real experts in some special conditions the experiences of many show indoors is not a good place for Chinese elms for the majority of us. Unfortunately, unscrupulous dealers seem to underestimate the difficulty in order to make more sales and many beginners get caught out. I'm beginning to wonder if Bonsai sellers are related to Used car sales people?
Having said that, yours is doing remarkably well so far.
The yellow leaves all appear to be the oldest and it is natural for some of the oldest leaves to die off. Not usually anything to worry about. Yellow leaves can also be an indication of changed conditions. If those older leaves were adapted to more sun they may now be not good at harvesting energy in the new light regime so the tree is scrapping them in favour of the newer, better adapted leaves. Again, nothing to really worry about. Just the tree adapting to new conditions. You may see a similar thing if the shade adapted leaves are suddenly exposed to more, stronger sun. If possible build up to full outside sun little by little over a few weeks.

What does worry me a little is the very wet soil. Watering according to a calendar (every second day) is not good. Roots that are constantly wet get infected and die. When that happens the top soon follows. Need to water according to soil moisture. Let the soil get almost dry before watering again. Frequency will depend on size of tree, size of pot, soil mix, air flow, temperature, time of year and more. At some times of the year the tree may need watering only once a week. Other times of year when the tree is growing well, humidity is low and temps higher it may need water every day, some bonsai need water twice a day. The only way to tell when is to check soil moisture. Not just the surface which can dry when the soil below is still too wet. dig a little to check or use a skewer/chopstick as a soil moisture probe.

The small holes in one leaf looks like some sort of pest damage. Probably a tiny caterpillar but indoor trees are subject to a range of pests and diseases that don't seem to bother outdoor plants quite as much. Personally I would not worry about 1 leaf with a few holes but if it gets worse or if that bothers you you should seek out some sort of pesticide to deal with the problem. Systemic insecticide is surest but not sure those are still available in UK. Pyrethrum is safer and should deal with most caterpillars but you may need to spray several times to get full coverage.
Leaf size can be an indication of changed conditions. The smaller ones are way back so whatever triggered that is now gone because newer leaves are bigger and healthy.

I've never used a stickon plant shelf. At least with your casement windows you will be able to reach the shelf outside. Provided it is large enough for the tree and the pot and strong enough to hold it long term it should work.
Note that outside conditions will be very different from indoors so watering regime will change.

"...What does worry me a little is the very wet soil. Watering according to a calendar (every second day) is not good. Roots that are constantly wet get infected and die. When that happens the top soon follows. Need to water according to soil moisture. Let the soil get almost dry before watering again. Frequency will depend on size of tree, size of pot, soil mix, air flow, temperature, time of year and more. At some times of the year the tree may need watering only once a week. Other times of year when the tree is growing well, humidity is low and temps higher it may need water every day, some bonsai need water twice a day. The only way to tell when is to check soil moisture. Not just the surface which can dry when the soil below is still too wet. dig a little to check or use a skewer/chopstick as a soil moisture probe..."

This observation by Shibui is something I can attest to. My Chinese Elm bonsai tree experienced a first winter here [last. year] in the Raleigh area of North Carolina that averaged 40 degrees [never getting to a dormant state - and having a caretaker who just kept the soil too wet during the winter]. This Spring I discovered the small pot-bound tree was not doing well when I peeked under the surface [packed solid almost black roots]. Doing much better now after a repot couple weeks ago - just trimmed off the dead branches the rotted roots created. Have posted an image of what the tree looks like before and after about 2 weeks post repotting.

 

[dhelix33]

"...What does worry me a little is the very wet soil. Watering according to a calendar (every second day) is not good. Roots that are constantly wet get infected and die. When that happens the top soon follows. Need to water according to soil moisture. Let the soil get almost dry before watering again. Frequency will depend on size of tree, size of pot, soil mix, air flow, temperature, time of year and more. At some times of the year the tree may need watering only once a week. Other times of year when the tree is growing well, humidity is low and temps higher it may need water every day, some bonsai need water twice a day. The only way to tell when is to check soil moisture. Not just the surface which can dry when the soil below is still too wet. dig a little to check or use a skewer/chopstick as a soil moisture probe..."

This observation by Shibui is something I can attest to. My Chinese Elm bonsai tree experienced a first winter here [last. year] in the Raleigh area of North Carolina that averaged 40 degrees [never getting to a dormant state - and having a caretaker who just kept the soil too wet during the winter]. This Spring I discovered the small pot-bound tree was not doing well when I peeked under the surface [packed solid almost black roots]. Doing much better now after a repot couple weeks ago - just trimmed off the dead branches the rotted roots created. Have posted an image of what the tree looks like before and after about 2 weeks post repotting.

I have moved the Chinese Elm outdoors today! New permanent home is on a table on the patio outside the sunroom it was residing in.

 

[MRB]

Your tree looks much happier than before
Unfortunately, I am still struggling with my tree. The yellowing process continues, and apart from that, some leaves have a burned look. I think one problem could be its organic soil which is compacted.
Despite losing leaves, new shots are almost all over the tree with a good growth rate. That branch in the last image lost all its leaves but now new shots are showing up.