For those pots growing a plant with a single stem, I mulch with fir bark pieces of about 3/8 inch, which helps prevent weeds and moisture loss. For plants sending up multiple stems from the roots, I do not use mulch. Al

I also mulch with a little ground pine bark in my container blueberries. The sun pounds them all day long and it helps a little to keep the moisture in, and the soil surface stays a little cooler IMO.

I mulch pots too, mostly using a pea gravel...my original reason was to stop or at least slow down squirrels and a (lonly-so far) chipmunk from digging.
It works quite well, and helps to retain some moisture too.

Rina

Add me to the list of those who mulch with Bark.
I never mulch deeper than 1 inch, though, and I pull back the mulch during the Winter.

Josh

Thanks everyone for your responses. I didn't think I was so smart that I thought up a new thing, but I wondered if there was some problem that I didn't think of. Since just about nothing would survive winter in a pot around here, pulling the mulch back for winter wouldn't apply to me, but maybe it is a good point for others with year-round pots. I have heard of people putting coarse rock on the top of soil in pots of house plants to keep cats out of them. Also there's the people doing it for esthetic reasons. I also wonder if it would make a difference in, say, pots of annuals that are planted thickly so the foliage eventually covers all the soil.

I find with a bark based mix (5-1-1), I don't need to mulch, since the soil mix itself is very mulch like. That being said, if people have issues with excessive heat and evaporation, using a non-porous mulch such as white stones would be appropriate.