Reducing soil temperatures when using a black, plastic training pot

[Ohmy222]

wood box?

 

[Wires_Guy_wires]

Thanks. Painting was my first thought too. I have a white marine topcoat already -- that provides UV protection and should be good on plastic -- and that I'll never use again. So that's free. And then I had planned on asking my neighbor for a cup or so of some Insuladd that I know he has leftover from doing his house with it. So free again. I just know that it wouldn't be good for a human to sit and breathe paint fumes all day, so I made the assumption that it probably isn't good for a tree either. It's good to hear that nothing happened to your trees. I guess the difference is that the trees will be outside all day and not in an enclosed space. If I do it, I should aim to do it, I think (maybe?), on a day with at least a breeze. Alternatively, I found a thick (7mm) aluminum foil tape for about $5 USD, which would be easy to appy evenly and there'd be no issue with fumes...

The thing with alufoil and alu tape is that it can get real hot in the sun too. You're reflecting onto something, that something will get hot, or you'll go blind from the reflection yourself. Just touch a piece of metal that's been lying in the sun all day, you'll probably feel that it'll be pretty hot. If you're going to use tape, I'd recommend that thinnest stuff instead of the 7mm thick stuff. Purely reflective material that doesn't refract light a lot, can cause hot spots or 'sun spots'. That's why matte white paint is usually used in plant laboratories; it reflects and refracts, so that light has a more even distribution.
Tree resin is a natural solvent, especially conifer resin. Turpentine originally comes from pine resin. Most plants breathe out esters (carbon volatiles) that give off a nice smell. Those can act as paint solvent on their own at the right concentration. Most paint fumes do not hurt plants that much, unless you keep them in an air tight cabin or something for a long period.
Latex paint doesn't have a lot of volatiles, so that stuff is safe even on your plants themselves. Not advisable though, to paint your plants.
Of course, painting in an enclosed space isn't healthy, so a breeze would be nice. Or do it in a parking lot or something. But we humans are in fact way more sensitive to those paint fumes than plants are. A coniferous forest in the blazing sun produces 100x as much of those fumes a day.
I would be very, very surprised if your plants were negatively affected by the paint fumes caused by spray painting a couple pots. Back in the days I've spray painted over 20 plants in a metallic blue color, and they all lived.

 

[Treemendously_Small_Trees]

I've found myself leaning towards more terracotta pots.
Although I'm in 6a, the summers can bring 90f days for periods of 1-2 weeks in a row.
The terracotta pots retain moisture and tend to remain cool for a period after watering. I'll water twice a day during the heat.

Terracotta pots actually cause soil to dry up faster as they are porous leading to small amoubts of water and air to pass through. Good thing about this is it is even less likely you'll over water your trees.

 

[Rabe]

I use terracotta pots that are slighty larger than the container. The sun doesn't hit the black and the container stays cool.

 

[bonhe]

I use terracotta pots that are slighty larger than the container. The sun doesn't hit the black and the container stays cool.

I had been using few things
1- white T shirt to cover the small pot
2- nursery net to cover the big pot
3- terra-cotta pots for some of my pines in training. They really like it.
4- place the small pots in the water basins
5- move the special needed trees to the appropriate place for them ( the coolest place in the garden )

However, in the last few years, I have been only using 3-, -4 and -5. So far, all my trees is happy
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[BuckeyeOne]

Terracotta pots actually cause soil to dry up faster as they are porous leading to small amoubts of water and air to pass through. Good thing about this is it is even less likely you'll over water your trees.

I find that with the terracotta absorbing the moisture and retaining it means less watering and a cooler pot. The transference of air and water is beneficial to the root structure.
This is similar to the usage of pond baskets to promote the movement of air and water through the root mass.

 

[bonhe]

One more thing. I have used humic acid granule quite a bit and it may have good effect on heat resistance as some sources found.
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[BuckeyeOne]

One more thing. I have used humic acid granule quite a bit and it may have good effect on heat resistance as some sources found.
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I've just become familiar with humic acid and this year will be my first time using it. I was not aware of its use in helping the tree with heat resistance. Good to know!!

 

[sorce]

I was just coming to mention, it may be better to just involve removing that black pot in your plan.

I personally, watch every Boxwood left in a black pot, worked or not, just die. So I've been reducing in spring, and repotting by fall with success.

Spruce, Juniper, Mugo, can take a little longer in them, but still, I won't cut off so much that they can't be repotted within 2-3 years.

I believe it is easier, safer, faster, more efficient to plan on removing it.

@penumbra the light trapped and bouncing around in the gloss is what we see, at least that what I understood.

Sorce

 

[plant_dr]

Just touch a piece of metal that's been lying in the sun all day, you'll probably feel that it'll be pretty hot.

Remember those playground slides that were made out of metal? Those suckers were a bout 20,000 degrees in the sun!

 

[DHass]

I agree with white paint. Everything in phoenix is white. I never thought of foil....

 

[James W.]

Growing trees directly on the ground makes a huge difference.
After that, anything to shade the pot helps.
Burying the pots in mulch works very well.

 

[bonhe]

I've just become familiar with humic acid and this year will be my first time using it. I was not aware of its use in helping the tree with heat resistance. Good to know!!!

I have to thank Smoke who introduced the benefits of humic acid to this forum about 10 years ago? Since then, I jumped right in this fantastic substance. It helps my tree a lot !
By the way, I did not see @Smoke post here any more ! I and a lot of people here will miss him
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[Cascading-Echinocactus]

Using a styrofoam cooler you can fill it with a few inches of water , put a rack (made from a plastic crate) in the water basin and place the tree+pot on top of the rack. The foam will certainly keep temperatures lower and the evaporative cooling that takes place daily, within the cooler, will lower the temperature as well.
To insure quick evaporation you could also include an aquarium air pump+air stone to the water basin. I do something similar to this, in order to cultivate Darlingtonia californica in Alabama zone 8.

A better alternative to this cheap setup would be a small cold frame or greenhouse with a quality evaporative cooler inside.