Summer watering to cool roots

[leatherback]

The pots get hot quickly if exposed to direct sunlight in the summer. To keep the pots and soil inside of them cool by watering means very frequent spraying and that can lead to overwatering easily. Root rot in hot summer is usually death sentence for most trees.

I doubt it VERY much.
Overwatering is a bit of a myth if you use proper open substrate.
Rootrot in summer is more often than not triggered by the rootball drying out too far, rather than being too wet I would say. You really have to try hard to kill roots by being too wet. It takes a long time.

 

[rockm]

I doubt it VERY much.
Overwatering is a bit of a myth if you use proper open substrate.
Rootrot in summer is more often than not triggered by the rootball drying out too far, rather than being too wet I would say. You really have to try hard to kill roots by being too wet. It takes a long time.

Spoken like someone not living in the southern US.

Yes overwatering to keep roots cool IS definitely possible even with free draining substrate.

That is because is extremely hot weather with high humidity trees shut down a bit. Some enter summer dormancy. That means they’re not really using water as much.

That means roots may be sitting in a lot of water depending on how much is applied and the local weather.

Here is the SE middle Atlantic states we’ve been getting extreme thunderstorms and heavy rainfall. It’s unpredictable where a storm will appear. That means if it you’ve watered to keep the plant cool that watering may be followed by a downpour that brings three inches of rain that last all night and the soil could remain soggy for 12 -18 hours at a time

I am not watering as much now as I’m cautious about keeping the trees too wet.

 

[PastryBaker]

Added to that Palm Springs gets crazy hot wind. It’s like living in a sand blaster. I used to work out there years ago.

More like a convection oven with the door left open and the fan going. And I should know, I am a pastry chef...lol

 

[PastryBaker]

I doubt it VERY much.
Overwatering is a bit of a myth if you use proper open substrate.
Rootrot in summer is more often than not triggered by the rootball drying out too far, rather than being too wet I would say. You really have to try hard to kill roots by being too wet. It takes a long time.

95% of my trees are in the lava. akadama and pumice mix.

 

[PastryBaker]

For those who've not spent any time in Palm Springs during summer, it presents a very unique environment where growing anything is concerned. During the peak of the summer heat, which can last for weeks, daytime highs of 110-120F mean that temperatures can still be in the high 90s at midnight. Anything you grow there needs to be able to handle that heat, sun or shade. The ambient temperature will not change by watering, except for a few minutes during evapororational cooling. So in my estimation, aside from shade, the most important thing is just the regular watering routine you have....and growing those plants which can take the heat.

I learned quickly about growing what does well here. The Phoenix Bonsai Society really helped me with that.

 

[PastryBaker]

I’m watering 4x a day minimum right now in the Inland Empire.

Right now I am once a day. The temps have been a tiny bit lower, so the larger ones can go a little bit longer. But soon it will be like last year, twice to three times a day. I still question why I live in this heat....lol Maybe I should move to Chino.

 

[leatherback]

we’ve been getting extreme thunderstorms and heavy rainfall. It’s unpredictable where a storm will appear. That means if it you’ve watered to keep the plant cool that watering may be followed by a downpour that brings three inches of rain that last all night and the soil could remain soggy for 12 -18 hours at a time

Spoken like a person not living in the atlantic rainbelt

Funny to hear people worrying about a rainstorm passing after water for someone living in a climate where some summers have continuous rain for weeks on end, and common fall/winter weather may include 2-3 months with rain falling near-continuously, not stopping for more than a few hours a day. Tell me more about trees sitting in a pot with water for 18 hours!

 

[oranjeaap]

Unless the water is significantly lower in temperature than the ambient temperature I dont see how (extra) watering will help cool down the plant much. And even then, because of the small pot, I doubt the effect will last longer than an hour.

Above certain ambient temperatures it might even be harmful, water has a much higher specific heat capicity than air and most substrates. If the water reaches a certain temperature while still surrounding the roots it might actually transfer more heat into the roots than air would.

 

[Khalero]

Spoken like a person not living in the atlantic rainbelt

Funny to hear people worrying about a rainstorm passing after water for someone living in a climate where some summers have continuous rain for weeks on end, and common fall/winter weather may include 2-3 months with rain falling near-continuously, not stopping for more than a few hours a day. Tell me more about trees sitting in a pot with water for 18 hours!

I second this. You really need to do your best or have bad drainage to cause root rot in the summers, especially in a climate of southern US lol.

 

[rockm]

Spoken like a person not living in the atlantic rainbelt

Funny to hear people worrying about a rainstorm passing after water for someone living in a climate where some summers have continuous rain for weeks on end, and common fall/winter weather may include 2-3 months with rain falling near-continuously, not stopping for more than a few hours a day. Tell me more about trees sitting in a pot with water for 18 hours!

What me worry? It's Just a passing rainstorm....

 

[coachspinks]

If you are under 70% shade cloth, do you feel you really need it? I suppose it would depend on the tree; California junipers grow in the Mojave, for example, and many conifers thrive in hot conditions. We never got as hot as Palm Springs in the OC, but I never found myself watering because of root heat concerns.

We are consistently in the mid 90s here in middle Georgia. It is humid. My shimpaku don't seem to be suffering with fill sun all day, but I do worry about the ones in smaller, 6" shallow pots. I did lose some random branches last year. Should they be under shade cloth?

 

[BrianBay9]

While not quite as extreme as Palm Springs, our summers are triple digit (F) days, no rain, and 30% humidity. With decent soil it is indeed impossible to over water during summer here. I water 3 or 4 times a day now that I'm retired and home consistently.

 

[PastryBaker]

While not quite as extreme as Palm Springs, our summers are triple digit (F) days, no rain, and 30% humidity. With decent soil it is indeed impossible to over water during summer here. I water 3 or 4 times a day now that I'm retired and home consistently.

Thanks. I have been to Fresno in summer, and it was hot and dry. Do you have much wind up there?

 

[BrianBay9]

Thanks. I have been to Fresno in summer, and it was hot and dry. Do you have much wind up there?

Not consistently. When a front moves through we might get a day or two of 15 - 20 mph

 

[rockm]

From a Mirai video on Facebook

 

[leatherback]

Just had half an inch of rain in 45 minutes dumped on us. What to do with this forecast.
My trees will all die...

 

[rockm]

Yeah kinda wimpy compared to what’s happening here all summer

https://www.cnn.com/2025/07/20/climate/summer-of-flooding

 

[rockm]

we got about four inches of rain in about three hours. This has been happening all over the Eastern half of the country The flood that killed a couple dozen people on July 4 is part of the same pattern.

 

[leatherback]

Not sure what the point is.

My point is, A singular water event is not an issue for trees in open substrate. It takes much longer to kill off your roots.
Once the pot is saturated in a storm, it is saturated. It does not matter whether that is an inch, two three or a whole bucket of water. When I water, I fully saturate the pot, similar to a big storm, And it will drain and the tree will take some up. Do not water and in a day of two the trees rootball is back to normal.

Half an hour drive north they received over 2 inches in one hour last night, which is where they got the brunt of the summerstorm. Our drainage system is built for 1 inch of precipitation an hour, so this causes localized flooding. Big difference, hete it is so flat it does not accumulate in one spot, so flooding stays most of the time marginal and confined to areas directly hit and/or the river floodplains (Where one is not supposed to build houses so all good). Last night just north of here.

 

[Mike Westervelt]

Andrew Robson routinely advocates thoroughly soaking trees, foliage, benches and the ground around the benches multiple times per day during unusually high heat events, Rakuyo and
Crataegus had little to no casualties during our insane heat dome event in 2021 when Portland reached a ridiculous 116F, while Mirai suffered what Ryan has described as catastrophic losses.
I personally have been watering everything every few hours when temperatures are above 95F for the last few years even though I'm aware they are shut down and not "using" water and have seen
no root rot or fungal issues.
Just my 2 cents, take for what it is worth