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.