Oh, P.S. --

I haven't seen anything yet that actually compares drainage in containers to drainage in the ground, or that compares the likelihood of rot in containers to rot in the ground. If anyone comes across a comparison like that, please let me know!

Very interesting stuff even if it is a little technical. Thanks for collecting it and posting it here.

The articles you posted can be extrapolated to say quite a bit about drainage in the ground compared to drainage in a pot (as I figure you already know). The area below the pot is just a very large soil pore. Comparing root rot in containers comparted to in the ground would be a little hard because so many factors (other than whether the plant were containerized...soil type, soil compaction, amount and frequency of water, evaporation, etc.) would have to be considered.

"Comparing root rot in containers comparted to in the ground would be a little hard because so many factors (other than whether the plant were containerized...soil type, soil compaction, amount and frequency of water, evaporation, etc.) would have to be considered."

Right. It sounds like it's a very complicated subject!

I still have trouble believing that a plant in a pot would be more likely to rot than a plant in the ground, in a general sense....and until I see some good evidence, I ain't gonna buy it. ;-) After all, raised beds are known by EVERYONE to be good for drainage concerns -- and raised beds are nothing more than huge containers!

I hope y'all can forgive me for harping on this subject a bit -- but since my yard is FILLED with containers, it's important to me!

Raised bed are very different from containers because raised beds don't have a gap at the bottom that stops capillary drainage action. The capillary action necessary for drainage is free to occur in a raised bed (with any kind of decent soil). A container is like a raised bed where the whole bed is lifted a few inches above the ground so that there is a gap between the bottom of the soil and the ground and drainage stops when the soil reaches 'field capacity' (still too wet).

That's a good thought. But....

1. if that gap is really such a detriment, then why does just about everyone in the world tell you to be sure that the pots do NOT rest directly on the ground?? Is that gonna turn out to be just old wives' tales?

2. not all containers do have that gap. For instance, I have several planted whiskey barrels that I intentionally put in direct contact with the soil, so that the roses' roots could grow down into the ground if they wanted to.

Interesting things to think about. I may have to do my own testing one of these days..... ;-)

1. The only reason I can think of not to rest the pot directly on the ground is so that roots don't grow down into the soil if a) you are planning to move the container later or b) you are worried about a big root expanding in a small drainage hole and completely blocking drainage or cracking the pot. This is not related to drainage and may be a competing issue.
2. Sounds like the whiskey barrel was a raised bed.

Well, a lot of people do recommend that -- and I can see the point somewhat, at least from the standpoint of avoiding blockage of the drainage hole -- but, in the sense of preserving the water column, maybe it's not such a good idea after all!

It's amazing how many things that are conventional wisdom turn out eventually to be completely counterproductive. Things that make ya go hmmmmmmm.......

Geez, no wonder I suck at container gardening. I didn't take physics in high school! J/K Interesting stuff.

Rebecca