How about wrapping the pots with this to keep them cool?
http://www.mastergardenproducts.com/palmthatch.htm

a 2 ft strip of aluminum foil is way cheaper than any materials so far.

Yes, I agree, but my husband won't go for the pot looking like that! I had thought of spraying them with metalic spray paint but it would also look kind of bad. Lesley

I wrapped mine in aluminum foil and it worked very well. I remember Joe Real made a suggestion to wrap them in a gold foil which would look better than plain kitchen foil wrap. A couple people last summer dug holes and buried their containers. You can use a therometer to check the tree's soil. At soil temperatures between 64F to 82F citrus roots grow well. The amount of growth is lineraly corrilated. 82.4F is suposed to be the best possible temperature for excellent growth, while soil temperature above 96.8F retards the growth of citrus. I really do not know if my wife liked the foil wraped trees or not, I did not ask. If you have the trees on your patio you can set the tree inside a larger decorative pot. This will give an elegant look and also block the direct rays of the sun from contacting the actual container. Millet

Millet is correct. Another option is to avoid the black plastic pots. Buy the thicker FeatherLite pots, they are more expensive but thermally well insulated, and they look really great, some would look like well carved decorative stone pots. I potted my bananas in them and they survive the winter outside. Citruses grow very well in these pots as long as you drill inconspicuous holes sideways near the bottom and only one at the bottom, and there is no need for aluminum foil or paint job, and why would you? I have several big black plastic containers that was given to me for free and can't part with them, so I use aluminum foil during the summer and remove them during the winter when using these black plastic pots. Wine barrels are made of wood, and wood are good insulation and so are very good potting container for citruses, and citrus grows very well on wine barrels when you pot them properly for size, so there is no need to wrap foil or paint the wine barrels. You will only paint the wine barrels mostly for decorative purposes.

Virtually anywhere in Texas in full sun in July and August will be too hot for citrus in containers, especially if they are getting reflected heat off bare ground or cement. My trees are shaded by a pecan tree in the hottest part of the afternoon which spares them the frequent exposure to 100+ degree heat. I also use companion plants growing in the same container with the trees such as tomatoes and peppers to help shade the pots. I have had a nice bell pepper crop for three years in a row from the same plants. I use what is available such as plastic and clay when my trees are smaller and build wooden planter boxes out of cedar or pressure treated pine for my larger trees. Clay is my favorite for smaller trees because it is porous and allows for better air circulation. I seem to have a tendency to want to hurry my trees to larger pot sizes thinking all the time that this will increase the tree size and yield, when I should be more content with smaller more manageable trees. I have run into some overwatering problems in doing this and always seem to graduate back down to a smaller pot size. I usually repot to a container that will afford about an inch of space around the rootball.

What about building a pretty wooden planter box to sit your tree with pot into? That would shade the roots and look great too!

Here is a link to show what I am talking about:

Here is a link that might be useful: Wooden Planter

I have hundreds of black containers and there is no way I am going to buy more. Since we are talking about outside in the sun in the growing season, these are a few of my favorite things...
I organize all my large container to where they are going to be outside, then the medium size.
Here is the fun part. I take 1 or 2 gallon cheep-o-black pots, cut three or four 2" holes evenly spaced around the middle upper third of the pot. Next 3/4 more 2" holes around the bottom third of the pot. I alternate and evenly space them. Fill bottom of pot with soil then pick a cool annual or creeping herb for your climate.
Then treat like a mini strawberry pot.
Stick the fist level of plants in the bottom holes, fill in to the next level of holes. Stick in plants and fill in. In the top I pick something low growing and that can take some dryer soil. My pic is Sedum.
I place them all around my containers and mimic the same annuals in my yard. In a month, about time the sun is at it's hottest they have filled in enough to protect.
Looks like mounds of color instead of hot dirty pots.
The result is very beautiful!

This workes very well here for me in NYC.

It also help with windy days-less blow overs.

On dryer days it keeps a little more humidity around the citrus.

On hot and humid days I spread them out a little, for better circ.

On colder spring and fall nights it keeps the roots a little more sheltered.

Thats my thing, and whats more fun painting or PLANTING....

Oh yeah, I almost forgot you have got get a few little containers,( even a old cap from a aerosol can will work) place them between and around the pots and fill with beer. Between the pots will make a perfect home for slugs.
The beer is non toxic and VERY effective in controling them.

There is something to be said about aluminium foil, my nasty squirrels hate it! I tear it in to 2"w long strips and criss cross it loosly over the top of my pots. It also looks very nice when the sun reflects off of it.

Good Luck, Mantis212

hi all, i'm a newbie with citrus. i now wonder if my meyers is in a to big a pot. i have had this tree since last may, had 25 buds,harvested 3 large lemons,so proud.now my meyers is in my bdrm w/SE sun,not hot but not to cool, its not real happy right now ,thought maybe because its winter & she has to be inside.shes in a pot,app.20 gal. should she be in or do better in a smaller pot,i'll do whatever is best for her,i love the thought of havin my own lemons ,even a few.any info would be appreciated,thanks ahead,molly

Molly, what size pot was your Meyer's in before potting to a 20gallon size?
How's your citrus doing otherwise? Any problems? If the tree is doing well, then there's no need to worry about the pot size. As long as you're watering properly, plant is getting enough sun, folaige is lush and green, then you're doing a good job and there's not need to worry..Toni

thanks toni, i guess i just needed that bit of "your doin it right" .molly

Molly, how is your citrus doing? I have all my citrus, about 20, in plastic pots yr round.
The important thing is the health of your tree..if it's doing okay, then there's nothing to worry about..Toni

I get it im 16 years late but my first thought wouldd be a wooden planter that doesnt hest up like plastic, plus if you get one msde of planks youll get air flow itll aerate your roots