Sun scorch or something else..?

[Haydz]

I recently picked up this maple from a pop up shop here in SoCal, I couldn’t say no. Now the plant is usally on my balcony and I have a sun blind to help with some stippled shade for my other maple but up until last week we have been very overcast and cloudy so I’ve had it closest to the open to get as much of that cloudy sun as possible, now where I believe i fucked up was we got an unexpected mini heat wave with blue sky’s, 85-95 F days, and a UV index of 10+ and this little guy was right there to take it all in, since then I have moved him back away and closed my sun curtain to break up some of that immediate sun for a “dappled shade” if you will… now where I am second guessing myself is this maple came in a soil I usually don’t work with, now I’m pretty good at gauging when water is needed and the whole top of the soil came covered in these river stones which seems to keep the moisture in pretty well but now I’m worried that im missing diagnosing sun scorch for over watered or a root problem… I usually only water when the top quarter to half inch is starting to get wet dry, (like it looks darker but when you pinch it in your fingers it kinda crumbles away without anything sticking to your fingers)

So now I take to the bonsai forums lol… what do yall think and what would yall do any and all recommendations are welcome

 

[nuttiest]

What side is the porch? If it gets direct sun the heat of the black stones is not good.
If you need a soil decoration find some Santorini stones, they reflect a lot of heat.

 

[Deep Sea Diver]

Dunno, doesn’t look like sun burn to me.

Possibly a water quality issue. @Bonsai Nut used to live down there, perhaps he can help?

Best
DSD sends

 

[Bonsai Nut]

It is very tough to keep Japanese maple in Southern California. The big culprits are:
(1) Bad water. Unless you have a water softener, your water out of the tap is likely very alkaline and high in sodium. My water out of the tap was 8.5 pH, when Japanese maples prefer water that is slightly acidic (like 6.0 pH). Using acid fertilizer will help, but not completely resolve this issue.
(2) Intense sun. You can solve for this with some version of shade cloth or sun covering.
(3) Low humidity. Combined with the sun, if you leave your tree outside on the wrong day, the leaves will crisp. If the Santa Anas are blowing you have to give it wind and sun protection - almost like a shadecloth tent - or the tree will burn up.

I tried many times to keep Japanese maples in Southern California, but was almost completely frustrated. I was able to keep a single Sango Kaku alive in a sheltered corner of my yard under shade cloth, but the tree never looked that great, and sadly, in the Fall the tree's leaves would dry up and fall off the tree without any autumn color.

 

[Haydz]

It is very tough to keep Japanese maple in Southern California. The big culprits are:
(1) Bad water. Unless you have a water softener, your water out of the tap is likely very alkaline and high in sodium. My water out of the tap was 8.5 pH, when Japanese maples prefer water that is slightly acidic (like 6.0 pH). Using acid fertilizer will help, but not completely resolve this issue.
(2) Intense sun. You can solve for this with some version of shade cloth or sun covering.
(3) Low humidity. Combined with the sun, if you leave your tree outside on the wrong day, the leaves will crisp. If the Santa Anas are blowing you have to give it wind and sun protection - almost like a shadecloth tent - or the tree will burn up.

I tried many times to keep Japanese maples in Southern California, but was almost completely frustrated. I was able to keep a single Sango Kaku alive in a sheltered corner of my yard under shade cloth, but the tree never looked that great, and sadly, in the Fall the tree's leaves would dry up and fall off the tree without any autumn color.

I use a filtered water system for all my plants, I closed my shade blinds I have over the porch that protect my other maple that went into dormancy way late with our warm winter here. I definitely think I left it exposed too long in the mini heat wave we had with UV indexed at like 10 I think fried some leaves.. I have it pushed back out of direct light and closed my sun curtain so it gets a soft morning light and then indirect the rest of the day. We are moving pretty soon and I don’t know how much sunlight our new place will get so I am going to be experimenting with some grow lights, who knows might thrive will update with those.

 

[Wulfskaar]

I've kept my shishigashira J. maple alive for a few years now. Morning sun and/or dapples shade is what they need. I have serious doubts about grow lights being helpful.

Generally, late summer through fall, when the Santa Ana winds are blowing, we need to really protect them from that dry wind. Bonsainut is exactly right, if you don't protect them, the leaves will get dry and crispy and fall off before the spectacular fall colors that J. maples offer in fall.

This fall, I'll be really trying hard to protect mine from those winds because I really want to see the fall colors.

 

[Bonsai Nut]

I use a filtered water system for all my plants, I closed my shade blinds I have over the porch that protect my other maple that went into dormancy way late with our warm winter here. I definitely think I left it exposed too long in the mini heat wave we had with UV indexed at like 10 I think fried some leaves.. I have it pushed back out of direct light and closed my sun curtain so it gets a soft morning light and then indirect the rest of the day. We are moving pretty soon and I don’t know how much sunlight our new place will get so I am going to be experimenting with some grow lights, who knows might thrive will update with those.

One year I tried 10 different JM maple cultivars that were supposed to be "full sun" or at least more sun tolerant than normal. They looked great in the spring until about June - when the first Santa Anas blew off the high desert. Every single one crisped - even under shade cloth - and there was little I could do about it short of bringing the trees into my house. They rebudded as if I had defoliated them, and looked good for a month or two, until the next wind event, when they crisped and died... every one.

And when you say "filtered water" I want to make sure you understand what you need to do. You need to use either a water softener that uses potassium chloride pellets to refresh the element (not the sodium chloride ones) or a reverse osmosis unit - preferably with a deionizer. Get yourself some cheap pH test kits and a cheap TDS (total dissolved solids) meter. Test your water out of the tap, then test the water after you filter it. All California water districts are required to release annual water quality reports. Check your water district and see what you are "supposed" to be getting, and compare it to what you actually get. My water out of the tap would kill 3' koi if I added 6" of top-off to a 6' deep pond without treating it first. Untreated it was very high in chloramine... which is ammonia bound with chlorine. I would not recommend using that on a plant, but Cal is worried about showers and kitchen water - not what would be best for irrigation.

 

[Wulfskaar]

One year I tried 10 different JM maple cultivars that were supposed to be "full sun" or at least more sun tolerant than normal. They looked great in the spring until about June - when the first Santa Anas blew off the high desert. Every single one crisped - even under shade cloth - and there was little I could do about it short of bringing the trees into my house. They rebudded as if I had defoliated them, and looked good for a month or two, until the next wind event, when they crisped and died... every one.

This year, I'm going to try to put mine in a plastic greenhouse thing before the wind events. I might put a bucket of water in there to keep it more humid in there during the worst days.

I really hate Santa Ana winds, not just for how they crisp bonsai, but for how they cause so many terrible fires.