Watering help in SoCal

StreamGrove

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This will be my first time caring for plants during summer here in Los Angeles. We are already getting heat waves in spring hitting 90s. I have my plants in a full sun area under a shade canopy I made that has a white 50% uv cover, and a 80% on the back to blockout afternoon sun. I will be setting up some wiFi soil moisture sensors here in a few weeks.

I have a wide assortment of plants, and the ones I am most concerned about are the Japanese Maples. I used to mist them in the evening but stoped after finding out the salt in our super hard water "7.4" pH, was making the leaves salt burn. I then read that both overwatering and underwatering can cause leaf tip burn. That burnt leaves on JMs in their first year in SoCal is common as they slowly establish to the climate and go through some heat stress. I have them potted in 1part pumice, 2 parts crushed pine bark, 3 parts Dr Earths Acid lovers potting mix soil, so they have great drainage. I let them dry out before rewatering, and once a month give them a deep watering of 1tbs white vinegar to 5gallon water to help wash some salt build up off the roots.

Others I have talked to here in SoCal with JMs say its not so much the hot sun that damages the leaves but its the dry santa anna winds mixed with the hard water that gives them a ruff time. So I guess I am overloaded with information regarding burnt leaf tips on JMs. How would you tell if the tips are burnt from overwatering compared to underwatering? If im not misting them and watering once every 4 days it would be from underwatering right?

Yellow leaves: If a leaf is yellow and falls off easily its from too much water or needs water? Compared to a yellow leaf that is crispy hanging on for dear life needing water or too much?

The things I need help understanding are brown leaf tips, and yellowing leaves. Garden wisdom greatly appreciated!
 

Shibui

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There's very little difference in outward signs of over or under watering. Over watering can occasionally cause root rot. When the roots die the tree can't get enough water so it dehydrates and the leaves turn brown. If the tree is under watered it can't get enough water so it dehydrates and the leaves turn brown. The only way to tell is to unpot and check the roots.
Root rot is rare when the tree is in a good, modern, open bonsai mix so I would bet on under watering as the problem. My area is probably similar to yours. It gets quite hot in summer - well over 100 here on hot days. In late spring and summer here I water all my trees every morning and every evening whether they need it or not. I'm pretty sure that more trees die from under watering than from over these days.
Proper watering is the key. Dry soil is hard to rewet. Most of the water just runs off and out the drain holes. It looks like you have watered well but only the outside is wet. Inside is still dry. Every day the roots suck out more moisture and the middle of the pot gets drier and drier until the tree suffers.
To water effectively in hot climates either water for a long time- 10-15 min each time - to allow proper penetration OR, more effective, water several times. Water all the trees then go round and water them all again then water a third time. Each time the moisture soaks in just a bit further until the soil has enough water for the day. Japanese masters talk about watering 3 times - once for the leaves, once for the trunk and once for the roots. pretty sure that's just a way of getting apprentices to do it properly.
Soaking the pots once a week is another way to make sure the soil is properly wet occasionally.
Yellow leaves that fall off easily can be from many different reasons - lack of light, lack of nutrients, nutrient imbalance, dry or wet.
Yellow leaves that are tightly attached can be the same as above but not yet dead enough to drop? In my experience sudden dry will cause leaves to brown but stay attached.
 

Bonsai Nut

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If you have the option, I am not kidding you when I say take one of your Japanese maples and water it with distilled water only. Compare how it responds to your other maples you are watering with SoCal water. I'm surprised you are getting 7.4 pH out of the tap. That actually isn't that bad. My water tested at 8.0 out of the tap (whenever I tested it) and the water utility annual safety report suggested it ranged as high as 8.5 (!)

If you have them protected from the wind, under shade cloth, and can keep the soil pH down, I think you may be ok. You can tell if the wind is burning the leaves if they look 100% healthy (dark green, etc) but the tips and margins of the outer leaves start to burn, while the inner leaves on the tree continue to look fine. If you are experiencing leaf problems due to root issues (over/under-watering) it tends to impact all leaves on the tree equally, or one zone/branch of the tree while all the rest of the tree looks fine.
 

John P.

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I’m in Laguna Beach, Orange County, so not as hot as some inland areas. I’m trying full shade (north-facing wall) on some this year to see how that goes. I’m also using pure seedling bark for moisture retention and water once a day in the morning.

I also wonder about fertilizer, too, as you’ll read that chemical fertilizers contribute to the problem.

I’d definitely try to keep your leaves dry. Fungal issues and all.

There are organic, sprayable plant sunscreens out there for nut farmers. I’m intrigued by the idea: https://www.foodforest.com.au/fact-sheets/fruit-and-nut-trees/sunscreen-for-plants/

Another link:http://www.pestgenie.com.au/Label/crop_care/Parasol _O_label.pdf
 

StreamGrove

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Thanks for the feedback. Being new to bonsai I only have about 4 different plants in traditional non organic soil. Those are far easier to manage and seem to have zero leaf issues regarding watering etc. My maples, wisteria, and a few pines are in an organic mix 1 pumice, 2 crushed pine bark, 3 dr earths acid lovers potting mix because I am using them as mother plants to propagate with, and those are the ones I am trying to work out right now. @Bonsai Nut distilled water sounds promising. I wonder if our city water is like yours in the 8pH range and my water softener is also working on the outside taps. Do you mist your maples with the distilled water or just water the soil?

@John P. My neighbor has some in the north position mostly shade that are pretty well established, (non container) Bloodgoods. I am trying that with my Emperor, and one Arakawa. That sunscreen does sound like a good idea!

@Shibui I think that was sort of the start of my problem was I got used to watering the non organic soil bonsai frequently and it was too easy to water the organic other ones thinking im helping them. Basically I ended up over watering the non bonsai and had to repot about 13 plants because I was getting fungus and all sorts of issues. Lesson learned! Kinda do wish I could have them all in non organic soil but that would be super expensive for all my plants at this time. I guess it's worth noting how mental the weather has been this spring. We went from dumping rain to dry mid 90s heatwave status over and over again. I had several wisteria and JMs arrive from the east coast during this time and they literally thought it was summer and all went green leaf, they are totally confused.

Some of my maples like the Orion, Dancing peacock and Arakawa have soft velvet texture leaves and others especially the Japanese Princess has crispy leaves. I am guessing leaf texture on all maples should be about the same?
 

John P.

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I’m in Laguna Beach, Orange County, so not as hot as some inland areas. I’m trying full shade (north-facing wall) on some this year to see how that goes. I’m also using pure seedling bark for moisture retention and water once a day in the morning.

I also wonder about fertilizer, too, as you’ll read that chemical fertilizers contribute to the problem.

I’d definitely try to keep your leaves dry. Fungal issues and all.

There are organic, sprayable plant sunscreens out there for nut farmers. I’m intrigued by the idea: https://www.foodforest.com.au/fact-sheets/fruit-and-nut-trees/sunscreen-for-plants/

Another link:http://www.pestgenie.com.au/Label/crop_care/Parasol _O_label.pdf

It’s only July 12, and my Japanese maples along a north-facing wall largely look crappy. Crispy. I have a weeping Trident maple cultivar that literally gets beat on by sun from 1-6pm and has no burnt leaves.

Frustrating.

Maybe I should give up on maples and stick with ficus, elms, oaks, and olives?

Nothing compares to a maple, leafed out, in springtime though.

I really can’t imagine using RO water for these trees every day.

Conflicted and frustrated here.
 

StreamGrove

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This summer has been insane! It has been a serious learning experience tending to many different young trees. My maples survived but had to relocate them to the east side of the house, they cooked even under shade outback. One day it hit 115 and they got microwaved =(
I have been experimenting with a WIFI Ecowitt WH51soil moisture sensor. Hard to find any practical guidance online for it. By default the AD is set to 70 for 0% humidity and 500 for 100%. I customized the calibration where 110 is set to 0% (time to water) and 220 for 100%, which is generally the reading I get after guving the plant a good drink.
Even though I have this all set up I have been scared to let them get to 0%. I have had to repot a few pines and had a few other plants have root rot issues. I have good draining soil, so I guess I am wondering if anyone more experienced with moisture sensors could give some advice about is watering at 0% would be a good idea.
Is that too dry for a contqiner plant in SoCal?
 

Mikecheck123

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This summer has been insane! It has been a serious learning experience tending to many different young trees. My maples survived but had to relocate them to the east side of the house, they cooked even under shade outback. One day it hit 115 and they got microwaved =(

What you have to realize is that temperature and evaporation rate have an exponential relationship. So an increase of 10 degrees can double the evaporation rate.

What this means for my climate and soil mix is this:
When it's:
80F I can water once
90F I have to water twice
100F I have to water three times
105F or more I have to water FOUR TIMES!!!

So 115F is truly challenging for thirsty trees. I wouldn't let anything get to 0%. I think you need to water more often.
 

Colorado

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I had this problem last year with dry winds and crispy leaves. I had much more success this year - my maples are still looking great going into fall. A couple tips:

1. Use 100% akadama for your substrate. It makes a huge difference.
2. This should go without saying, but if you’re using 100% akadama you need to have a spaghnum moss top dressing on the pot.
3. I left them in morning sun/afternoon shade until temps hit 85 degrees and then I put them in full shade for the rest of the year. They might get 15-20 minutes of sun in the very early morning, but not much.
4. Try standard Japanese maple seedlings rather than a cultivar. I haven’t given up on the cultivars by any means but everything I’ve seen says the straight species is the toughest.

E12B2C36-D59C-4216-B6F9-D54258CBD119.jpeg
 

StreamGrove

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What you have to realize is that temperature and evaporation rate have an exponential relationship. So an increase of 10 degrees can double the evaporation rate.

What this means for my climate and soil mix is this:
When it's:
80F I can water once
90F I have to water twice
100F I have to water three times
105F or more I have to water FOUR TIMES!!!

So 115F is truly challenging for thirsty trees. I wouldn't let anything get to 0%. I think you need to water more often.
Thanks for the tips. Would this only apply to pure bonsai soil with excellent drainage? I ask because 75% of my plants are not typical bonsais and are in a soil mix of pinebark fines, azealea potting mix, grit/pumice. My concern is that since there is organic potting soil in the mix that this will lead to rootrot since I have/am dealing with root rot with some plants.
 

StreamGrove

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I had this problem last year with dry winds and crispy leaves. I had much more success this year - my maples are still looking great going into fall. A couple tips:

1. Use 100% akadama for your substrate. It makes a huge difference.
2. This should go without saying, but if you’re using 100% akadama you need to have a spaghnum moss top dressing on the pot.
3. I left them in morning sun/afternoon shade until temps hit 85 degrees and then I put them in full shade for the rest of the year. They might get 15-20 minutes of sun in the very early morning, but not much.
4. Try standard Japanese maple seedlings rather than a cultivar. I haven’t given up on the cultivars by any means but everything I’ve seen says the straight species is the toughest.

View attachment 333344
Nice pic, looks super healthy! The plants I do have as bonsais are in a soil mix of pinebark fines, monto clay, and a little bit of maroon lava. Nice touch with the spagmoss. I could see that working well as top dressing. I had bad results when mixing it with potting soil, major root rot troubles.
 

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