Okta

Im going out this weekend and gettin me some 5 gallon tubs. Fill it with 1 part fert to 4 parts soil with a nice layer of rocks at the bottom, i figure that should work well.

plainsman1963

Actually, I have been working for years with my local extension office and they have finally convinced me that putting rocks or other low permeability materials in the bottom of your pot is actually counter productive.
What happens is you make what they call a "perched water table" which means that the rocks or whatever holds or disrupts the water flow and you have a water saturated space which is what you are trying to avoid.

I would recommend you make sure your soil has great drainage (30-50% perlite) to begin with and forget about the rocks.

You can go here and on the right side of the page is a link to a video segment called "container annuals" where she briefly touches on it.

Good growing,
Plains

Alpha

Taken DIRECTLY from the Grow Bible:
"As a rule 1/2 inch of gravel or another suitable, high draining mixture at the bottom of the pot will help to prevent this problem and will also stop the plant from drowning if it’s over-watered."


Isn't that some kinda sacrilege?

plainsman1963

I prefer "changing with the times".

I know, it's been something we've done for generations. Along with the rusty nail for iron...etc.

It took a long time for them to convince me, but when they brought out 2 identical containers, filled one with soil mix and one with a rock layer and then the same soil mix, then poured in the same amount of water into each pot (ending the pour at the same time), they convinced me.
The container with the soil only drained faster than the container with the rocks. They also did it with sand as well. Same result.

It's ok with me if someone wants to put rocks in the bottom of their pot, it's not like I get a commission for every convert.

Just thought I'd share what my extension office shared with me.

Peace,
Plains

Alpha

So perlite, rocks, gravel... anything with lower premeability then the soil will get this result? That's interesting plains. I was just giving you a hard time bro . Looking at it from a logical stand point, you'd think having the draining material under the soil would prevent a water table of any kind from forming. I'm having a hard time understanding how the drainage material causes the problem.

plainsman1963

To be honest with you, so did I.

I have no idea if perlite would do the same, never tried it. Just rocks and sand.

Think of it like a 4 lane highway turning into a 2 lane. As the water searches for ways to go through the rocks, the remaining water backs up as it waits for it's chance to drain down. This causes standing water, which saturates the soil, which can encourage root rot and insects.

Again, I'm just relaying what the extension office is saying (like I could make up "perched water table").

Good growing all,
Plains

Alpha

You'd think that the material that doesn't absorb the water would be the 4 lane in the scenario. I just don't get it . Looks like it's time for a little experiment of my own . I wonder if the kind of drainage holes in the pot matter. You know, how some have the one in the center, and other have 4 notched out in a square like patter? Putting a permeable material under the soil makes sense for drainage to me... but what's that prove eh?

davepotdave

personally I put a few holes at different levels of the pot , partly so i can check the soil moisture and I have a theory that it may help get air to the roots just thought I 'd add that in

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Pepperpot

Hey davepotdave,

Interesting idea! The roots love oxygen....humm...I'd like to hear some more about this.

PP

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plainsman1963

For an experiment? No, I wouldn't think so. As long as you get two of the same kind.
Exactly. That's the point. A permeable, as opposed to an impermeable rock would be fine. Something like crushed rock wouldn't be good. It wouldn't allow liquid through it so the water would have to squeeze through crevices and cracks, which would back up the water leaving a perched water table.

I agree with Dave about the different heights as well. I have holes drilled into the sides of my 5 gallon buckets, and my 4 gallon milk crates (which holds 5 gallons of soil, go figure) have triangular holes all up the sides and bottom, so I just punch holes in my trash bag liner all over. Easy to check soil moisture at different levels.

Since I'm VanGogh, I decided to draw a picture of a perched water table. The white lines are supposed to be roots with their feet wet. Feel free to snicker and guffaw at your leisure.


Plains

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