Put a piece of carpet or a folded blanket on the ground, and lay the pots down on it. Have a close and understanding friend grab one rim, while you grab the other, and try to pull them apart--it helps to pull on one side, then the other, and repeat. Hopefully, after 10 or 15 lusty tugs, it will work itself loose. Sometimes it helps to heat the outside one with a hairdryer just before tugging. Banging alternate sides of the bottom of the outside pot with a rubber mallet also helps, but there is more risk of breakage. In my work, I have had to deal with this many times, and in about 5% of cases, one pot still winds up breaking.

Alternatively position a short thick cane 4-6 inches long into one of the drainage holes under the bottom pot (right way up). Lift both pots very slightly and gently tap down onto the cane. This usually separates them.

Just be careful that the cane doesn't slip through the upper drainage hole and poke you in the eye!

4-6inches long? :-)

Oops! Someday me learn read good!

You could have been lying down looking at it, doing it ;-))

Um...urrgh...oof...OW! : D

LOL !