I've had excellent results burying pots for summer, clay and plastic. I've done it for 3 reasons, so plants don't tip over during storms, the roots don't get so hot when the sun doesn't shine on the pot, and so they could be easily retrieved to take inside or into greenhouse for winter.
Overall, this has not been as satisfactory as burying plants without pots & digging them back up to save for winter, for several reasons. The pots are so dirty on the outside, and I've ended up having to dig much bigger holes for a few plants to be able to get under the pot to sever the roots that had grown through the drain holes. In those instances, there ended up being more digging than just digging up the plant without the pot.
A few have had potting soil, which did not go well, I assume because of the uneven moisture movement. If you can use some "good dirt" from a garden area, not dry, dusty, lifeless regular dirt from a mowed area, that is what I do because the results are better.
There are no rocks here, so that's not a concern. I wouldn't trust the mere confines of a pot to contain something I was concerned about spreading. I tried that for spider plant and it got away from me anyway.
Some discussions about this
The thread "Winter survivors & plants in ground for summer vacation" in
Cactus and Succulents forum
Many pics of this in progress at the time in this discussion:
The thread "Shade plants are on summer vacation." in
Houseplants forum
ETA: Ground dirt is HEAVY. There's a limit to the size pot you want to fill with this unless you have some very strong helpers.
