Maybe do a lasagna bed next time? Your pots are probably deeper and have less surface area, that is why they aren't as hot. Maybe next time, build your raised beds higher and not as wide. 4'x4'x10"? I'm not a very seasoned gardener, but living in Tucson, I've not noticed my soil in my ground beds having much issues with the soil heating up too much. Last week, I put compost and soil around all the plants, then today, I mulched with shredded newspaper. I mulched moreso for the evaporation of water to slow down since I water with 1/4" soakers. I just set up my first raised SFG bed today so we'll see if I have the same issues as you.

mulch mulch and more mulch is the answer to soil moisture retention and temperature control mulch keeps the medium cooler in summer and warmer in winter.

len

Here is a link that might be useful: len's garden page

In a really hot climate raised beds might be the wrong way to go. The advantage of raised beds are early soil warming and better drainage. I doubt either is an issue for you.

What you might consider are sunken beds instead. This utilizes the insulating properties of the soil as well as it's water retaining properties to the advantage of hot climate growers in pretty much the opposite way raised beds work to the advantage of cooler climate growers.

I will say honestly, that I'm not too fond of using treated lumber for raising food crops in. There is some question that such "treating" can leach out into the soil -especially in a hot climate.

But I also have a problem with soil drying here - and can appreciate what desert gardeners contend with, as I have done some limited gardening in our local desert (planted trees - nice grapefruit growing country). But mulch and more mulch.

Also - one other thing comes to mind - I layer the bottom of my raised beds with heavy cardboard - this helps keep the water from draining too quickly. I also use peat moss mixed with compost as my planting medium.

When planting new seeds or small plants, try a layer of vermiculite over or around them to keep the surface soil moist.

One thing comes to mind - reading old copies of Organic Gardening - there was an article about desert gardening, whereby, it was suggested that hay bales be placed around the growing area (wind protection), and the dirt scooped out and fill planting soil put in above, so that plants are grown deeper in the soil - I'm not sure, however, the one who wrote that was familiar with the desert soils that we have in California either.

Just my 2 c's.

Bejay

Ditto mulch - it sounds eminently reasonable. I've never heard of sunken beds but boy what a great concept - it makes sense in theory anyway -

Maybe dig down 12 inches or so, and then build up 8 inches of planting material. You could plant in that, and mulch over the top. The soil would definitely be cooler and retain more water.

I feel like converting one of my beds to a sunken bed. What a neat idea.

Our native ancestors used the sunken beds methods and it worked great. IF I WERE YOU I WOULD TRY THIS METHOD AND TAKE THE TREATED WOOD OUT OF THE GARDEN... BILL W.

Thanks for all of the tips. I would very much like to try a sunken bed, but unfortunately that is not very practical in my current location. Given that, it sounds like lots more mulch may be the way to go. Thanks all!

One problem I have is that the soil in the raised bed seems to get too warm during the day, even while using a shade cloth and mulch.

What type of mulch are you using? How thick of a layer? What type of soil are you using? How deep is it? 6 inches? Etc. Are your pots glazed or plastic? All you need for the sides of your bed is pine lumber. Cheap. Otherwise you might get lucky and find material on Freecycle.org as others have in this forum. There are endless possibilities for raised beds:

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rthomp
Raised beds do not retain water as well.
The insulation idea is okay if you use a foil surfaced insulation(face out) but you need to go below the surface some and use insulation that is approved for below ground usage. Typically found being used for foundations ...
It is waterproof but water can seep through the joints; a layer of 6mil plastic will reduce that a lot. One can reduce the costs and install time by skipping the insulation and just using the treated lumber with a covering on the inside of 6 mil plastic. Also needs to be below ground, some anyway(I know how hard the surface can be there ... ); get it down an inch or two somehow.
For mulch, try using reflective mulch, esp. under/around the plants. It can be covered with regular mulch for appearance sakes. Heavy duty Al foil works but does not last long -might make it one season if it is covered. Aluminized poly-film lasts longer. Check at the local garden center(s) or failing that, online.
The third thing is to install either a soaker or drip & mister watering system. If the plants are not very susceptible to mildew/mold problems, misters will keep'em cool although it can waste a lot of water. Phoenix, as you know, is a dry heat and misters are fairly common so it might be worth it to you. Misters are in addition to either soaker or drip. Drip is best for small numbers of plants as it can get out of control maintaining it for many.
I use soaker hose buried(a must!) under the mulch and, where practical, under ~ 2" to 6" of dirt. It has worked great here. I do no misting but that is because of the area's weather(hot & humid) and waste of the resource.
Be sure to water properly -too much is just as bad.

hth...

Raised beds can be created to retain moisture well if prepared properly. For instance, the use of recycled plastic lumber will maintain more moisture than anything "breathable" and not sealed such unsealed brick, cinder blocks, unsealed wood, tree branches, etc.

You can always incorporate water retaining granules or mats. The use of 2-3 inches of mulch will help exponentially. It is better to have good drainage than to not have good drainage. Plants recover better from dehydration than they do from root suffocation from too much water. If you're going to build a new bed, make it higher so you can have a deeper bed. The deeper the bed, the more water it will retain.

rthomp - I live in Phoenix too, actually I am building raised beds now and had been wondering about soil / heat & drying. I posted a thread here on the soil forum, and most were saying mulching is the way to go. I also talked to Brian, who is the owner of Whitfill Nursery this weekend (on his radio show). He told me that with raised beds in Phoenix area, you want to go with 50% native soil (which is heavy clay) and 50% compost. He said to toss in maybe 5% vermiculite or perlite, just to help with water retainage. Also to use at least 3" of mulch, if not more.

(I've been doing TONS of research the past few weeks) lol

I put an ad on Craigslist for compost, and am having 15 cubic feet of compost delivered for $45.00. Native soil is free, and the vermiculite will be under $10.00.

Good luck. :-)