Japanese maples suffering from heat stress

[Frogman777]

Hi everyone

Firstly - happy new year and wishing you all the best for 2025.

My friend is currently house sitting for me and has sent me these videos of my two Japanese maples. One is a bloodgood and I’m unsure of the other cultivar. They both seem to be suffering from extreme heat stress and I was wondering about what my next steps are and their possibility of survival?

The majority of the leaves have dried up on one but some have survived, notably ones facing direct light. On the bloodgood, the majority of the leaves have started turning dark green with the edges curling up into a pinkish brown colour.

I think realistically the watering has to be increased, but aside from that I am just worried about losing them both.

Context - I live in Melbourne, Australia. Both have been sheltered from direct sun largely, but my balcony faces south so there is strong afternoon light.

Apologies in advance for the poor pictures - they’re the best my friend could send.

Thanks in advance for your help.

 

[Brian Van Fleet]

Pix are not good enough to tell for sure, but underwatering usually shows up on the edges of leaves. If I had a guess, your friend missed a day.

 

[JadedEvan]

I would be maybe a bit more worried about desiccation than underwatering. The crispy edges suggest to me that these might be in a very dry and/or windy environment? Can you share more about the wind exposure that these might get?

For reference - I live in the Netherlands, which is generally a very humid and wet country. I observe that my maples really need to be sheltered from the wind (as it is VERY windy here). Failure to protect them leads to crispy edges and eventually unhealthy foliage. Think about how and where maples grow in nature - understory trees, well shaded, little wind. The more you can replicate those conditions the better the outcome.

 

[Frogman777]

T

Pix are not good enough to tell for sure, but underwatering usually shows up on the edges of leaves. If I had a guess, your friend missed a day.

Thanks so much mate - I’ll try upload some better pics when they can provide tomorrow.

Definitely think that’s likely to be the case given we’ve had very high temperature recently.

If that’s the case, would you say the recoverability chances are high if I simply wait til next spring? This is happening mid summer FYI.

 

[Frogman777]

I would be maybe a bit more worried about desiccation than underwatering. The crispy edges suggest to me that these might be in a very dry and/or windy environment? Can you share more about the wind exposure that these might get?

For reference - I live in the Netherlands, which is generally a very humid and wet country. I observe that my maples really need to be sheltered from the wind (as it is VERY windy here). Failure to protect them leads to crispy edges and eventually unhealthy foliage. Think about how and where maples grow in nature - understory trees, well shaded, little wind. The more you can replicate those conditions the better the outcome.

Thanks so much! I wouldn’t be surprised if it’s this either. When initially transporting this home, it had heavy wind exposure but I saw no signs of stress for the last 2 months.

However, we have had some dry heat and do get relatively strong winds every now and again given the location of my apartment. Australia is generally very hot for JMs, and it has been between 25-39 C these last two weeks I’ve been away.

I’ll get onto monitoring the wind once I am home. Currently in Japan, so will also pay more detailed attention to how these trees are growing wildly here.

Would you say that either way I just sit and wait?

Both are relatively well established trees and, while in pots, are at least a good metre tall. I assume they will likely survive if this is just dehydration of the leaves, but I have to wait til spring for there to be new growth.

This is happening in mid summer FYI.

 

[Bonsai Nut]

When I see crisped foliage margins like in your photos, I normally think too much sun and/or too much arid wind. You can help determine the cause if the upper and outer leaves on the tree show the most damage, while the inner and lower leaves are still healthy. Damage that is due to drought will be much more uniform.

Japanese maple trees do best in protected, understory environments with dappled sun and protection from wind. This is even more the case with variegated foliage, which can even crisp in dry wind in total shade.

 

[Brian Van Fleet]

T

Thanks so much mate - I’ll try upload some better pics when they can provide tomorrow.

Definitely think that’s likely to be the case given we’ve had very high temperature recently.

If that’s the case, would you say the recoverability chances are high if I simply wait til next spring? This is happening mid summer FYI.

Yes, likely it will be ok so long as you keep the roots watered well. There isn’t really anything more you should do right now aside from proper siting and watering. Like @Bonsai Nut said, JM are understory trees, thriving with cool roots, dappled sunlight, and minimal wind.

 

[Frogman777]

When I see crisped foliage margins like in your photos, I normally think too much sun and/or too much arid wind. You can help determine the cause if the upper and outer leaves on the tree show the most damage, while the inner and lower leaves are still healthy. Damage that is due to drought will be much more uniform.

Japanese maple trees do best in protected, understory environments with dappled sun and protection from wind. This is even more the case with variegated foliage, which can even crisp in dry wind in total shade.

Thank you so much, appreciate this.

As I understand, it is the inner and lower leaves that are generally doing better while the upper canopy seems to be fried. I guess we’ve somehow had issues of arid wind and it’s a shame I haven’t been in town to be able to take note.

I’ll be able to upload some more photos today so please let me know if those change anything - otherwise, appreciating the help as always.

 

[Frogman777]

Yes, likely it will be ok so long as you keep the roots watered well. There isn’t really anything more you should do right now aside from proper siting and watering. Like @Bonsai Nut said, JM are understory trees, thriving with cool roots, dappled sunlight, and minimal wind.

Thanks so much again mate - I doubt it would be sunlight unless the angle of the sun has drastically changed due to seasonal change, so it will have to be arid wind.

I’ve read in places that defoliation is a good idea to encourage budding, but given it’s summer and your comment above, I imagine it’s best to just let her be?

Thanks so much and hoping you’re having a great day.

 

[fredman]

I’ve read in places that defoliation is a good idea to encourage budding, but given it’s summer and your comment above, I imagine it’s best to just let her be?

I'm next door in NZ.
My 3 red maples (about 10 years old) also dried up some...to much in full sun.
Every year i'm frustrated by the long internodes they throw out.
This year I did something "radical" i've never done. Because most of the leaves are crisped up, I removed all the leaves...and cut all new growth off. They we're all back to where they started in spring.
I dunked them in a bucket of water (and left them in for several hours) every time they needed watering.
They've all since grown beautiful shorter nodes and smaller leaves now.....first time it happened since I had them.
I've placed them under a silver fern for dappled light and they'll spend the rest of summer there.

 

[Wulfskaar]

When I see crisped foliage margins like in your photos, I normally think too much sun and/or too much arid wind. You can help determine the cause if the upper and outer leaves on the tree show the most damage, while the inner and lower leaves are still healthy. Damage that is due to drought will be much more uniform.

Japanese maple trees do best in protected, understory environments with dappled sun and protection from wind. This is even more the case with variegated foliage, which can even crisp in dry wind in total shade.

This is my exact experience with Japanese maples in southern California.

 

[Frogman777]

Hi everyone, thanks for all your help so far.

Attaching some more photos - please let me know if these help better determine if we’re dealing with windburn here and the odds of the tree recovering?

The cultivars are bloodgood and (I believe) Seiryu.

Many thanks again.

 

[Frogman777]

I'm next door in NZ.
My 3 red maples (about 10 years old) also dried up some...to much in full sun.
Every year i'm frustrated by the long internodes they throw out.
This year I did something "radical" i've never done. Because most of the leaves are crisped up, I removed all the leaves...and cut all new growth off. They we're all back to where they started in spring.
I dunked them in a bucket of water (and left them in for several hours) every time they needed watering.
They've all since grown beautiful shorter nodes and smaller leaves now.....first time it happened since I had them.
I've placed them under a silver fern for dappled light and they'll spend the rest of summer there.

Thank you so much for the insight mate and good to meet a neighbour.

I don’t have the space on my balcony to dunk these in a bucket of water - would you say gradually spraying the soil with water would achieve the same purpose? Ie, a deep soak.

Follow up question - how much of your maples dried up? Just trying to gauge how screwed I am.

 

[Frogman777]

This is my exact experience with Japanese maples in southern California.

Amazing, thank you. Following from the photos above, looks like it’s most likely due to windburn.

The upper canopy looks fried, but the lower ones look like they’re doing ok. I guess all I can do is wait til spring, right?

 

[Weta]

Looks high off the ground, is the area venting heat? , heaps of glass reflection.
Also people can forget to water at night and water in full sun basically cooking the roots..

 

[Frogman777]

Looks high off the ground, is the area venting heat? , heaps of glass reflection.
Also people can forget to water at night and water in full sun basically cooking the roots..

Apologies if I’m misunderstanding, but I think the heat is a bit more stagnant than I’d like it to be as the circulation isn’t as good as it could be. Definitely a good 1.5m off the ground as this is how I could give it the most space.

Wouldn’t be surprised if it’s the windows possibly reflecting a lot of heat.

Generally I do water either in the morning or afternoon and avoid watering when the sun is out.

How can I check that the roots haven’t been fried? Just uncover a bit of dirt and see how they look?

 

[Wulfskaar]

Amazing, thank you. Following from the photos above, looks like it’s most likely due to windburn.

The upper canopy looks fried, but the lower ones look like they’re doing ok. I guess all I can do is wait til spring, right?

Since it's summer for you, it might be possible to get some new leaves growing in. Not sure though.

I've read that J. maples do best with morning sun, rather than afternoon sun. Mine are kept in dappled shade under a large tree. Since you're in an apartment, you don't have much choice. So... you might look into making sure it's a little better protected from dry wind and too much sunlight. You might consider a shade cloth for controlling the sunlight it gets on the hotter days of the year. Also, I've read that spraying the leaves with a fine mist can help them retain moisture during hot/dry periods.

Good luck!

 

[Frogman777]

Since it's summer for you, it might be possible to get some new leaves growing in. Not sure though.

I've read that J. maples do best with morning sun, rather than afternoon sun. Mine are kept in dappled shade under a large tree. Since you're in an apartment, you don't have much choice. So... you might look into making sure it's a little better protected from dry wind and too much sunlight. You might consider a shade cloth for controlling the sunlight it gets on the hotter days of the year. Also, I've read that spraying the leaves with a fine mist can help them retain moisture during hot/dry periods.

Good luck!

Thanks so much mate! I’ll have to use a shade cloth to help cut off any excess sunlight and help protect against the wind to stop this happening in the future.

I’ll wait until spring - trees look otherwise quite healthy so I’m assuming the drying up is wind + heat + the tree trying to survive.

Hope you and your family have a great NY.

 

[Bonsai Nut]

This is my exact experience with Japanese maples in southern California.

I used to live in Southern California. It was my experience there as well. Once the Santa Anas start blowing, and that dry air starts flowing off the high desert, all bets are off. If you don't have your JM in complete wind protection, your leaves are going to crisp - even in total shade.

 

[Weta]

My amateur 2cent opinion.
A 10min deep soak would be my first port of call, in shower or bath if lacking outside space, lifting dirt will just cause more stress at the moment.
Get pot down to floor level. (careful of placing directly on hot concrete, in Oz I'd be worried about even the colour of the pot lol.
Id be looking at ferns etc to surround to act like a moist microclimate, they will also give hints of extreme conditions before the maple.
I try never to water in the morning and if I do the tree goes inside or full shade for the day.
Good luck.