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I'm thinking about going with grass clippings. I've been using them on some of the bare patches of hydrophobic dirt about the place and have been doing some good. When the planets line up right, I can put coffee grounds down first and grass clippings on top of that and that seems to do some real good. I'm starting from scratch in some spots because the winter rains managed to scour the top soil I generated previously and am back to hard cracked earth. Grass is growing back in.

In the pots I'm trying out these hollow ceramic spikes my wife got for me. They come with plastic adapters that you attach an old plastic soda bottle to and it lets the water from the soda bottle leak through the unglazed ceramic slowly. So far so good. I didn't see the droopy leaves on the dwarf peach trees in the couple of hot days we had. The real heat is yet to come. Haven't seen single digit relative humidity this year yet but we will be there soon enough.

I used to be able to locate potted plans under shade trees. The aspiration from the shade trees would mitigate the lack of humidity some and of course the shade kept them out of the sun. Saved a few hardy potted plants that way in triple digit summers.

Best of luck to you. One hot day when you can't water can kill off quite a few plants.

to sense
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If it's that hot, wouldn't the plant roots stay cooler in the ground than in a pot? Is your native soil something (sand?) that doesn't hold water?

That's what I experience here. Our summers are hot and humid though, not dry air, and I have clay soil with lots of OM which holds water well. When temps are in the 90s, even big pots dry out and need watering daily, but things in the ground can go weeks without a drink. Smaller pots need water twice/day.

Karen

I live in an apartment complex, my tiny 6 foot in-ground garden got full really quickly this year, so now I have about 10 pots with hot peppers in them.

Pots may do better than the garden because I can position them for morning sun when it gets really hot, the garden just gets blasted and I can't do anything about it unless I want to buy shade cloth or something.

Gotcha. Back to your original question about mulching pots:
I only grow flowers in pots. For decorative flower pots, I just usually use wood mulch, pine fines if I have them, which I usually do.

Straw makes a good mulch too. Seems to keep things cool and conserve water well. I've not used that in pots, though I think it would work as well as in the garden.

Karen

What would be the effect of a 1"-2" layer of Perlite, Turface, or Pummice? I know it would keep the soil cool but I do not know about the effects on moisture. Those materials hold a lot of moisture but they also drain very quickly. They are white, too! I just have no way to guess what a layer of one of those would do, hoping to find somebody with some knowledge on the matter!

I will try straw if nothing else seems better, but I would think a layer of coarse pebbles would keep the temperature under control pretty well, if I can get the sides of the pots shaded especially.

Thanks for the help thus far.
-Phil

For mulching pots, I use sphagnum moss. It tucks in nicely around the plants and allows easy watering but keeps the soil moist and cool. But then, I live near the bush so it's easy to go out and harvest a bit. I keep it over the winter and re-use it until I need more.

Mulch just applied to the top of the containers is not going to do very much to moderate the soil temperatures. The entire exterior surface of the container will be exposed to both ambient air temps as well as the sun and that will heat up the soil. A light colored container will reflect sunlight rather than absorb it, so if you can, go with white or beige. Wooden containers, because they are porous and breathe, also absorb less heat than either plastic resin, terra cotta or ceramic.

Not sure there is any really efficient way to keep the heat down other than sinking the containers into the ground, which on a balcony is going to be pretty darn hard to do!! You may just have to resort to watering more frequently......FWIW, nurseries have to deal with this situation all the time. There is no simple solution.

I hear that terracotta is porous enough to allow some cooling, enough that painting them white may not be beneficial. I will be painting my plastic containers white as soon as the weather stabilizes, for now I want them to heat up as easily as possible.

I may fit some frost cloth to wrap around the terracotta a couple times, this would shade the sides and allow air movement.

Still need to decide on mulch for the tops though, I may go with coarse turface or perlite, or I may try straw or soaked paper. It is hard to predict which of those might be most effective in dealing with heat. I dont want the material I use to end up wicking moisture, is a major concern. I think 2 inches of turface would hold enough moisture to help insulate the pots, but if it dries too quickly it may wick into the air.