false bottom for big containers

Winston Salem, NC(Zone 7b)

Sorry if this has already been covered somewhere... I couldn't find another thread in my search.

I got a very pretty and very large glazed ceramic pot last year. It is about 24" tall and maybe 18" dia. Last year, since I didn't want to use up 3 bags of potting soil to fill it, so I put an upside-down 5 gal bucket (drilled full of drainage holes) inside it, and then put a round piece of MDF that I happened to have around, also drilled full of holes, on top of that (d'oh!). No surprise- with 20/20 hindsight, the MDF soaked up the water and collapsed.

What do people usually do with these large containers? Fill them completely? Any ideas for an inexpensive but lasting material to use as a false bottom for it?

Also, with glazed containers, should I be concerned about them cracking in freezing weather? I'm in 7b.

Hammond, LA(Zone 8b)

I put a broken up paver or two in the bottom of mine. It keeps the pots from tipping over and allows me to use less soil.

New York, NY

You don't need a false bottom, just a bunch of Styrofoam or peanuts with landscape fabric over the top so the roots don't get down. It's not perfect but it will do. If you are planting annuals you won't need much soil but if you are planting a perennial, a shrub etc., make sure you give it enough room to root out.
You are probably okay in 7B but if it's expensive, you might try putting it on a piece of wood over winter if it's on patio stones. If it's on the ground it's probably okay. I've had one in NYC without a problem for five years while my neighbors lose theirs regularly.

Winston Salem, NC(Zone 7b)

Thanks for the quick reply!

I have used landscape fabric (it was the 'commercial' kind- used for french drains, etc, not the weed-block kind) in the bottom of pots before, and it seemed like it impeded the drainage... I know it SHOULD let the water through fine, but I switched from that to pieces of screen instead, sometimes doubled up. Do you think that that would that let roots through too much?

For this pot, it will just be mostly annuals and some shallower ground covers. Coleus, sweet potato vines, creeping jenny, and maybe some sedum if it seems happy in there.

When mixing annuals and perennials in contains, what about planting smaller pots w/in the larger one? (thinking about this for things like sweet potatoes... where I wouldn't want to leave it in there over the winter for the tuber to rot, but wouldn't want to tear up the roots of the perennial) Is this done?

Tonasket, WA(Zone 5a)

I put the peanuts (styrofoam) in baggies and tie shut, so that when I remove them in the spring the peanuts don't just fly all over, and the bag can be reused for several years. I have used 75% shade cloth over the bags of peanuts with good success.


Winston Salem, NC(Zone 7b)

Good idea to put the peanuts in bags! I'll try that. Thank you.

New York, NY

Landscape fabric should not prevent drainage but if you read the sticky post about drainage... well it's a bit of a science. Screen sounds fine.

If you are mixing, use shallow-rooted annuals. The sweet potato, if you second pot it, will need a lot of room. I've never done that but I don't see why you can't. It depends on the perennial as well. You could try putting up a vertical block but in the end, I would probably treat the perennial as an annual unless it was a big shrub of some sort and then I wouldn't worry too much about the roots assuming it's not a root-sensitive plant like clematis. If it isn't sensitive and you disturb some root in late fall, it's probably not a problem. If you do lose a lot of root, trim a bit off the top of the plant in winter (again depending on the plant) so it doesn't have to work as hard come spring. I hope that makes sense.

Cincinnati, OH(Zone 6a)

I use empty small water bottles or pop bottles, about 12 or 16 oz sice. No plastic fabric or anything- as you fill with potting mix, a little will fall between the bottles, but it's very little. Has always worked well for me. I've done that for years.


Portland, OR

I like the plastic bottle idea. I also have been putting packing peanuts in bags mainly because I like reusing them. Hate putting them in landfills!

I haven't used any screening of any sort. Why would that be necessary?


Windsor, CT(Zone 6a)

When I worked for a landscaping company that made up planted containers for clients, we used mulch in the bottom 1/3 of the pot. At the end of the season you just dump the whole thing into the compost.

You don't have to worry about freezing temps with your pot now. You just don't want to leave it out over a whole winter filled with soil exposed to the elements. When water freezes hard, it expands, and that's what busts ceramic pots that are left out. Sometimes you can leave a pot outside upside down, but if there are any tiny holes in the glaze you run the risk of water getting in there and damaging it. And never stack on top of each other ceramic or terra cotta pots that are stored outside, they expand & contract with humidity & temperature, and will probably break. Just put a piece of plywood in between them if you need to pile them high.

Many of the big & beefy Vietnamese pots that are available now are supposedly safe to leave outside with the soil still in them. But if you love your pot, don't risk it.

small town, MN(Zone 4b)

My sister always uses crushed aluminum cans in the bottom of her large pots. They use up some space plus give her great drainage. You should see her pots they bloom their heads off and look stunning with assortments of annual flowers.
Forgot to add this also keeps the weight down for when you want to rotate the pots.

This message was edited May 1, 2010 8:14 AM

Chewelah, WA(Zone 5a)

This message was edited May 28, 2010 4:21 PM

Thumbnail by woofie
Yukon, OK(Zone 7b)

You can also put a terra cotta pot upside down in the bottom. Choose a size that fits your needs and that works great for drainage too!

Bay City, MI(Zone 6a)

Actually, 9 of 10 'drainage schemes' don't work or are counterproductive, but in this case there is a sound scientific basis for agreeing with what the poster immediately above this post said.


Vieques, PR

I'd set the upside-down pot up on three pot shards, to make 100% sure it drains properly.

This set up acts like a pot of a depth from the top of the soil down to the top of the upside-down pot, with wicks all the way around, to the "floor". Maximized aerated root space, plenty of moisture.

Bay City, MI(Zone 6a)

The only potential problem with the set-up is it substantially reduces the volume of soil your plants have available for root colonization. This can be a plus if your container is too big for the plant material you selected and your soil is too slow (draining). Hopefully, we all understand there is no such thing as 'over-potting' when we're using the free-draining soils that support no perched water; nor would there be a reason to employ the overturned pot-in-pot technique with these soils, other than to reduce the volume of soil required to fill the container.

FWIW - you can achieve the same result as the overturned pot-in-pot technique by simply employing a wick through the drain hole and filling the pot with soil.


Cincinnati, OH(Zone 6a)

The main reason this old lady uses those empty pop bottles to occupy space is to decrease the weight of the thing so I can move that sucker.


Winston Salem, NC(Zone 7b)

I do use a pretty free draining soil, and the intention was not that it needed better drainage in itself, to reduce the volume of soil I needed to use b/c the pot is very large-over 2' tall. The soil in there is around a foot deep, which is what I had last year and everything preformed well. So I wanted to be sure what I used to take up some space wasn't going to hinder the drainage, or turn into a science project under there by the end of the summer, etc.
I'm in the middle of renovating the spot in front of the house where it sits, so I'm glad it isn't all the way full. It takes 2 to move it as is.
Here it is- planted all planted up. The sweet potatoes don't really show yet, but they'll cascade down the sides.

Thumbnail by monkapotamus
Vieques, PR

Don't all soils perch water at the point where surface tension of material = g force?

Bay City, MI(Zone 6a)

I suppose that a case could be made on a technical basis that any water, even the water that makes a soil barely damp is perched water. Water 'perches' in containers when the sum of the forces of adhesion and cohesion of the water molecules is greater than gravitational flow potential. Technically, surface tension is a partial function of cohesion and is part of the equation, but not the entire answer. In the discussion about the occurrence of PWTs in container media and their negative consequences on plantings, we're concerned with the water at the bottom of the container that forms a contiguous table of varying ht and that is dependent on soil particulate size.

PWTs are virtually a direct function of particle size. As the particle size of the soil increases, the ht of the PWT decreases, until at around a particle size of .100" (just under 1/8", which is .125") it disappears entirely. You can see it's no coincidence that the ingredients for the gritty mix I use so much of were selected because they are all right at or just above the .100 limit (the bark is usually a little larger to allow for its slow breakdown) so the soil would hold no perched water.


Vieques, PR

I think I understand. Total adhesion force "A" is directly proportional to the ratio of particle surface area to particle volume. The force of cohesion "C" is constant. Gravitational flow potential "G" is proportional to the total single mass of water subject to C, with gravity a constant. In practical terms, for a pot of given height, tiny particle size can cause A + C to offset G entirely (ie, PWT = height of soil), but as particle size approaches 1/8", A+C offsets G virtually not at all (PWT = 0", ie, at bottom of pot).

Wicks can reduce PWT height also, but in a different way, by allowing more water to remain subject to both C + G simultaneously (ie, in the wick), instead of forming a drop, which occurs when G = C.

Bay City, MI(Zone 6a)

OMG - Lol - I'm not going to sort through all that unless you make me! ;o) I'll just take it for granted you've got it right. If you're that familiar with the physics of water movement/retention in soil, what'd'u ask ME for? ;o)


Vieques, PR

You've taught me all I know --just seein' if I got it right.

Wauchula, FL(Zone 9b)

I have a 12' aluminum skiff that no longer floats at my home on a swf barrier Island. I want to make a planter out of it! I have been interested in the ideas for a bottom filler since it would take a lot of soil to fill it. May try the plastic bottle idea!!!

Chewelah, WA(Zone 5a)

This message was edited May 28, 2010 4:22 PM

Austin, TX

I'm going to try several of these ideas as I have tons of pots and terrible soil, all caliche. I have raised gardens too. I' which now as I'm older wish were 2-3'! Some pots that need moving may be candidates for the bottle idea, some long narrow ones need weight at the base or they topple (won't buy those proportions again) and I like Al's gritty mix too. A friend who watered for me once coounted some 120 pots. :) This is an old fountain I planted, it has a neat papyrus and some things that will hang sown as they grow.

Thumbnail by sylguy

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