I think it's an excellent point! There are confined spaces in nature where plants can take root. And does starkly highlight the strangeness and added degree of difficulty of plastic in regard to confining plants. Drainage/air is the issue. A 'natural' pot like a crack in a rock, crook of a tree trunk, wouldn't be made of impermeable plastic, and would be extremely unlikely to have a flat bottom.
I took some pics of "naturally potted" plants at Sloss Furnace in Birmingham, AL in 2013:
A determined tree:
Ferns:
Misc plants:
(If ever in the area, it's free, and fascinating.)
An unglazed clay pot automatically decreases the level of difficulty when confining a plant to a pot, but does have the disadvantage of being heavy, breakable. And unless it's an orchid-style pot, only has 1 hole in the middle.
One advantage a plastic pot has is the ability to add whatever size hole is needed, wherever it's needed. Most of my plastic pots have a chunk nipped out of the bottom with a pruning nipper, especially those that only come with 1 hole in the middle.
All of my pots have holes of some type in the bottom. After watering, allowing a few mins for dripping, I tilt each pot toward the biggest hole and a shocking amount of water always comes out still, even if I wait a couple hours. And even the unglazed clay orchid pots will drain off water if tilted toward one of the side slits. I've been moving all plants that aren't too big to this kind of pot, buying a few at a time. I would love to find some much bigger ones.
