You are right to worry. That is too hot.

Shade your pots in some fashion. Light-colored paint, a board shading the container, white
adhesive paper wrapped around the outside. If you have clay pots, can you just set the plastic
pots inside?

Elevating the containers by an inch or so will increase circulation and cooling.

Josh

Hmmm.... Not a bad idea to place the plastic pots in the larger clay pots..

They are currently hanging so they have a lot of circulation and still reaching very hot temps.

Also I am considering pulling them back from sunlight. Say back to getting 4-5 hours of direct sunlight in the mornings only with indirect light for the rest of the day. I have some Jalapenos that seem to be doing really well this way.

What would the plant symptoms be of hot soil ?

Death. Boiled roots.
Limp leaves, yellow leaves, crispy brown leaves.

Definitely try pulling them back to morning sunlight and indirect afternoon light.

The worst that could happen is that your plants become a bit stretched and leggy (etoliated)
as they chase the sun. The peppers might not be as hot, either, but I think you can control
this by not over-watering.

Josh

Dig a hole as big and deep as the pot...if you can. Put the pot in the ground. Ground temps here in Florida stay around 75. I put some of my pots in the ground this year and it helps... a lot.

sam

I am in Phoenix and have not had such temps in my pots. Speaking of high temps, we have not broken into the 120s in quite some years. But we will usually get over 115. Luckily it has stayed pretty cool so far this year. I put mulch in my pots just to keep some moisture in them, it helps stuff sprout and keeps the soil cool. If you put stuff in the ground mulch will almost certainly be necessary.

Just my two cents.

Farnell, are your pots plastic and exposed to sun during the afternoon ? I was actually surprized at the high temps. I have a professional digital thermometer and just stuck it into the pot soil about 4 inches down and went "wow".. It was surprizing...

The forecast is for 98F on friday.

Regretfully i am in a second story apartment so I do not have the ability to put my plants in the ground...

My plan currently is to place my plastic pots inside clay pots to act as sun shields. I might even figure out a way to use 2 clay pots and put styrofoam insulation between them. I will test a few solutions with real soil temp monitoring.

Choose terra cotta over plastic pots if it's that hot. Terra cotta evaporates water more quickly than plastic and keeps temps down better.

Yes plastic pots and not so much afternoon sun. If your plants are facing west you may have a hard time with them. The sun is the hottest in the afternoon. Most of my plants get morning and early afternoon sun. I only have tested my pots for moisture with my finger and they were not even warm. I hope you have good luck but I fear the hot afternoon on your plants.

I have a morning sun up to about noon spot I can place them. I did have them where they got morning up to about 2pm but I have pulled them back now. The temp drops very quickly in the pots when the sun is not directly on them. Im going to transfer them from plastic into Terra cotta pots and then place the Terra cotta pots into a even bigger Terra cotta pot with a air gap between the 2 to shield them from the sun. That should really do it.

While I had considered the air temp in Phoenix in growing my plants, I had not considered pot/soil temps.

O.k. Now I feel like a fool. I just stuck my finger in one of my pots all the way to the third knuckle and realized it was pretty warm. It was one of the ones that didn't have mulch.

At least the plants in these pots are doing pretty good. I guess I'll transplant them to a mulched area in the garden.

Sorry for opening my big mouth.

Yea, thats what surprized me ! They were growing pretty good, but no doubt soil down 3+ inches was reaching 103F. In the center of the pot. And these are big pots !. Watering them makes it way worse as the heat gets transfered way better from the outside of the pot inwards. If you use a thermometer you would be surprized just how hot they are.

No doubt I am going to go overboard and transfer them to a terra cotta pot for a number of reasons including evaporation cooling, and then place these pots into even bigger Terra cotta pots to shield them from the direct sun and leave at least a 1/4 air gap between.

Im also going to use some Perlite on the top of the soil to shield it from the direct sun. Its bright white.

Overall that should bring my temps into a good range. I will be testing after I go and will report here the results..

The real question is is 5-6 hours of direct sun enough ?

W O W.....

So I transplanted my 4 pots into Terra cotta. I gotta tell you, those pots are stupid expensive at home depot. $15 each.

This also allowed me to add some slightly acidic soil too :)

Im stunned..

My soil temp is 71 degrees yet the air temp is 80. This is caused by the evaprotive cooling effect with the wind and low humidity and the water in the pots. That is amazing. So I am sure that Terra Cotta is the way to go in high heat enviroments as its a natural cooler.

I also added a 1/2" of perilite on the top of the soil. This will keep the sun from heating the very dark soil as it hits it from above. The Perilite will also act as a insulating layer keeping the heat out and any latent coolness in the soil. It will also reflect light back up to the leaves rather then absorbing it into the dark soil.

The next few days will be interesting. I will measure my soil temps and see what kind of results I get.

Of course I did transplant a bunch of plants and that might be a issue as some were fairly young... I think the Terra Cotta, Bigger pot, Better soil and perilite layer will all make for a very nice change for the plants.

Just watch out and keep an eye on them. When it does get hotter (20F more to go!) those pots can dry out in almost day.

Indeed I will.. The overall effect from the evap cooling provided by the pots is amazing.. Its 95 out and my pot soil is 69F. Amazing..

I did a youtube on it showing what i did...

http://www.youtube.com/watch?v=mLLV6nUHcHc