I doubt that will work. You have a few inches above the mulch layer to absorb heat.

That heat has nowhere to go as it is insulated.

The way I look at it is keep containers off hot surfaces with cheap wood scraps and since it is hot, use cold water to irrigate and bring temps down.

Shade cloth set up to shade the containers rather than plants could work as well.

I guess I am feeling fortunate to live in zone 5 where I only worry about hot temps for 2 months. ;-)

How could you set up shade cloth that would shade the containers but not the plants?
Anchita, we are in the same climate zone. I have to garden in containers ON CONCRETE on the west side in FULL SUN until the last rays of the sun go down, so I sympathize with you. The heat is incredible.
I have learnt what plants can take it, and I go with those. It has taken several years to figure it out. I tried hibiscus this year. The plants could take the heat, but the blooms literally COOKED, so I gave them away.
Some of my plants require watering twice a day on the worst days. I'm willing to water as often as they demand. And the dog days are yet ahead of us!!!
What are some things you have found that will grow in containers in Texas' own special version of hell?

-- How could you set up shade cloth that would shade the containers but not the plants? --

Imagine a piece of cardboard laid up against the container. That would shade the pot and not the plants. A shade cloth built into a wooden frame can do the same thing, but can be made to look nicer ;-)

1939 here, ZIP 76712

This is more of an experiment than anything else for me.

Username, I see your point, and might try to see if I can come up with a form of the shaded container technique that works for me. Still, I do think the present arrangement is worth the effort if it helps keep the temperature even marginally lower. I'm keeping a close eye on these containers and will take care if this begins to have an adverse effect on them.

Eldo, I agree with your approach regarding choosing heat tolerant plants and would appreciate knowing which plants have worked for you in the situation you have described. This is my first year of serious gardening, so only time will tell which of my plants will take the heat well. I have Salvia, Lantana, Verbena, a Coral vine and a couple of succulents in the hottest and sunniest part of my patio.

Utsharpie, thanks for your suggestions about painting the pots and the circulating water. I might paint the upper part of the pots that is above the mulched basket area to help with the heat-reflection.

I think that basket-of-mulch setup will help even if it is not ideal. The top part of the pot will absorb just as much heat as it would if there were no insulation, but the rest of the pot will absorb less heat.

I think the water idea would help, but I don't believe that circulating the water adds any benefit if you're not cooling the water--still water should work just as well. Actually, I think sealing off the tubing with just air inside and forgetting the water would be even better, since air is a worse conductor of heat than water.

If I were to use those laundry baskets, I might wrap them--inside or out--with a layer of aluminum foil or light-colored paper or fabric (those are in descending order of likely effectiveness), then cover what looks like would be a couple-inch gap between the top rims of the pot and basket (perhaps using the same material) to block air convection. Then I wouldn't use the mulch. That would leave a good-sized pocket of pretty well-contained air around the pot.

Question--is there mulch in the bottom of the basket, under the pot? I'd think that sticking the pot right down to the bottom of the basket and just filling the sides with mulch would work better, since more of the pot would be insulated and I don't believe mulch under the pot does any good, as the ground should absorb heat from the pot, not transfer it to the pot.

I hope a ninth-grade science teacher will correct me on some of these ideas.

well if you have a large container holding your water circulating it thru the tubing helps transfer more heat than stagnent water in a tube.

and it takes more energy to raise the same mass of water compared to air 1 degree in temp, so water is far better an insulator than air.

Hi, Anchita. We are in the same climate zone. All the plants you named sound good. If you want to Google Texas Superstars, all those plants have been tested by A&M and proven to be tough. All my plants are in pots on concrete facing west. This year I have pentas again for the 4th or 5th year. The purple (or violet) doesn't seem as hardy as the pinks and reds. Plumbagos are heat-proof and are one of the true blue flowers. Cutting-grown coleus (not the seeded varieties) do well. Esperanzas. Maui red ixora (gorgeous tropical). Blue daze (evolvulus). Ornamental sweet potatoes. I even have some sun-tolerant caladiums from www.happinessfarms.com up against a wall which protects them from direct sun from about 3 PM on, and they are thriving. Since these are container plants, I will admit some have to be watered twice a day, depending on weather conditions, but most do well with a good watering once a day. I can do it in about 25 minutes.
Next year I am going to have coleus only. There are so many wonderful cultivars, and the cutting-propogated ones don't mind dreadful heat and sun as long as you don't let them get too dry. Usually we think of the darker colors as being more hardy, but even the pale greens do all right with careful attention to water needs.
This is my first year for plumbago, and I am thrilled with it. I have been told it will bloom non-stop until frost, except after the occasional shearing to keep it in bounds. It tends to get floppy. But after it's pruned back pretty severely, before you know it it's back bushier than ever and blooming its head off.

sorry i meant water will be a better conductor of heat than air...sorry...

meaning the water will absorb more heat than air in a tube thus reducing your container heat better than air in a tube

Your plants are likely to be perfectly fine without any intervention on your part! That has certainly been my experience in the over twenty years I lived in SC (8b). I never once 'cooled' a containerized planting, even under the harshest of conditions.

Many of the plants listed above are very heat tolerent, and there are plenty more where they came from! Follow eldo's advice and avoid those that are likely to bake, fry, and sizzle and you will probably be well pleased.

Thanks for the comments and ideas, everyone.

Eldo, I really appreciate your input about the heat tolerant plants. I will probably add some of them to my growing container "garden" later in the year or next spring. I do have some Coleus in a shadier spot, and I'm especially excited about the prospect of having Plumbago and Esperanza!

I set my containers in groupings so that the heat lovers are in front and shade the pots behind them. For the first time this year I have placed pots of tomatoes to the rear of each grouping so that the pots are shaded and am surprised to see how much this improves tomato growth and productivity. From now on that is the only way I will grow tomatoes. Another tip for featured stand alone large pots meant to make a statement. Purchase some weed barrier cloth; the type that one side has a black suede feel. This can be easily sewn on a sewing machine. Cut two pieces to fit around the pot. Place a layer of poly quilt batting in between the two pieces of weed barrier cloth and stitch enough to secure all in place. Now tie this around the pot with raffia or string. This will insulate the pot both from heat and winter freezing. If attractive plants that spill down the side of pots are used it is barely noticable.

utsharpie, you want to keep the heat from going INTO the pot, not draw it out. The plant isn't generating the heat, it's coming from outside. You want a BAD conductor, and air is a worse conductor than water, I believe.

I had some cheap press board copies of Monet paintings that I leaned up against my E.B.'s...looks great...kind of campy!>) Keeps those black boxes cool and certainly a conversation piece.

what about heat comin from the top of the soil? wouldnt water pull this heat as well as block it from the sides?

seems water would be the best choice

The ground is a heat sink (the further you dig, the cooler it gets, right?), so I don't know about "heat comin from the top of the soil". Contained air would "block it from the sides" better than water; water better than, say, solid metal.

Its not beautiful but it works. Wrap the pots in heavy duty alumnium foil curve it around the pot and fold it over the edges. Or buy and use only white cermaic pots.

Is the idea that the foil reflects the heat away from the container?
It may work, and thanks for posting the tip, but I'd rather not have any container plants than have aluminum foil wrapped around them.

I use ornamental potato vines to protect the 'afternoon sun' side of my pots. Just prune them like I want them. They really make a difference. Pots are black...1/2 whiskey barrel size. I have also used moss rose, and purslane will work but I HATE Purslane it because it is so invasive!!! I have used the foil and it works but is "tacky". Also found some sunbathing mats made out of very small reeds at Big Lots for 99 cents each and wrapped them around the pots and they worked great and looked good to. They don't take up space or water or plant food like the vines do...but the potato vines are certainly cheaper. It was 106 degrees here a couple of weeks ago and nothing [tomato, cucumber, eggplant, hibiscus, bell pepper] wilted. They are in full sun and I have added the vines a little further to the south side of the pot where the sun begins to hit it about 11:30 am. You will have "umpteen" cuttings available from just a couple of plants. The black one came up this spring in a pot that I just left on the south side of the house through the winter so that was a freebie. These Texas afternoons are hard on everything!!! Good luck, Mary