Is this only in Gritty mix, Mike?

I thought conventional wisdom on this forum was to avoid anything in the bottom of pots in order to:
-give roots more mix room to grow in
-avoid elevating a potential perched water zone

I've heard some people use old plastic soda bottles. Honestly the idea of putting anything 'unnatural' like styrofoam or plastic feels ..well..unnatural. Rocks seems counterintuitive if you're trying to make it lighter. I suppose it might be a good use for the 1/2" plus bark pieces that are sifted out when making mixes.

Hey, Mike, sorry we got disconnected the other day!
I will try calling you this evening, around 7:00 your time.

In very large containers, I've used soda bottles and also over-turned pots.

Josh

I use nothing at the bottom of mine. Not needed IMHO.

They are correct....the idea of improving drainage by putting material on the bottom is not true. Use a fast draining mix. Do not use MG "moisture control" whatever you do.

when I saw the title I thought, "what is this, a trick question? Of course the answer is potting medium." Then I realized it was for those monster pots. I usually don't put anything in the bottom. I do a pot within a pot and just elevate the plastic pot so that it is flush with the top. That makes plant maintenance easier in the long run since you can usually just pull the nested pot out and do whatever you need to do. However I have been known to use blocks of rigid foam insulation stacked up to take up space or to set the nested pot on. When you have a 3 foot tall pot filled with bedding plants, you don't need 3 feet of medium depth for roots.

I HATE the fact that Miracle Grow puts all that crap in their products. I won't buy their Perlite or moisture control stuff. I do like their plain potting MIX and organic mix but I prefer the Pro-Mix stuff.

Yes, this is for large containers, such as this half-barrel....

When I eventually figure out what to plant in this tall and very heavy 9.5 x 18 pot, I'm thinking of using packing peanuts half-way up in the bottom. Not for drainage, but to make it lighter, to save the mix and because roots probably do not need to go that far anyway. Do they?

Are we 100% sure ghost poop is inert?

Lol..Ghost poop///lol

You know, I never gave the packing nut much thought, but if Al sees this or anyone familiar with drainage, I would think it does have some positive affect for drainage too?

Does not mix fall between the peanuts too the bottom causing a wicking affect where the roots are not occupied, or will eventually do so?

I've use packing nuts before and have had to pull them away from roots eventually..In fact. many orchid growers use them to fill spaces in pots but the roots will wrap right around them..

Mike

I once used packing peanuts to lighten a pot for the fern that now occupies the half-barrel in the previous image. Here's an old pic of the roots with the styrofoam in the mix. I don't use it anymore because it's a pain to unpack! haha!

In some of my on the ground containers I use sufficient calcined clay to cover the drain holes in an effort to restrict access to pill bugs and earwigs (unproven).

My assumption is (also unproven) that the clay's attraction for water will help to minimize perched water.

Zeuspaul

meyer....you are getting quite a variety of answers here. Perhaps it would be best to let us know why you brought this subject up, and what you are trying to accomplish. Your second post inferred that you did not need the "extra space". That is one reason someone might block off some space....saving on potting mix for one thing.

I was musing one day Fireducj and this thought or curiosity came up...

It is quite interesting to see what others use and their reasons why....

I love different ideas and I should of even asked for pics of various pots that many fill the bottom space with..

In fact I will take a pic once the sun comes out and show one of my such pots that I filled with just plain ole pine mulch on the bottom with to conserve my mix and lighten weight.
'Not only that but I also feel it's an extra benefit to my already made mixes that virtually hold no perched water. But in an event if I am a bit lazy in making my mixes incorrectly that holds perched water, at least the bottom layer of mulch pulls the perched water away, at least I think...
I have made what I thought to be a very good 5.1.1 mix and found much water at the bottom of my pots along with dying plants.
So I took these plants back out and used pine mulch straight from the bag and the repotted with the same mix to find my mix did not stay as wet.

Instead of amending the mix once again with ingredients I had run out of, this was a great solution in my case.

I've put mulch at the bottom often, leaves, rough compost... just beware it will decompose much faster than you think, likely over the course of a single summer if plants are outside. This will alter the bottom layer so it's exactly the opposite, tiny particles. As this happens, it will be come increasingly more heavy.

Tiffany...Great point brought about about using certain things..One must be mindful of how much something can break down and actually impeed draiange...Good to see you.

Mike

I get 6-9 cords of beetle-killed pine for firewood every year, which yield a couple cubic yards of bark. I use this for mulch around the garden and extensively in my containers. I put the larger pieces in the bottom of the containers - up to 1/3 the volume, agitate that with the normal potting mix to insure there are no large gaps and air pockets, then use smaller pieces (1" dia) in the rest of the pots.

Its interesting to find that the roots of what ever I plant I have in the container will grow into every possible opening in these large pieces of bark - they must be deriving some nutrition, and as the pieces get damp, they retain moisture as well.

The containers do tend to get heavy.

David, the roots are seeking air, and the easy passage through such crevices. The nutritional value is 'locked up' until it decomposes, which would indeed be happening constantly though likely glacially on the surface of each piece at first, and more deeply as the microbes do their work (hence the increased water retention later.) Bark decomposes much more slowly than shredded wood mulch.

Glad the distinction came up. I was assuming shredded pine wood, but could have been bark (or even needles.) My comments about decomposition speed were in regard to shredded wood, not bark or needles. Either way, once soil becomes significantly more water-retentive from decomposition, however long it takes, the dangers of overwatering/underdrying come back, seemingly overnight.

The decomposition of wood, if happening significantly in a pot can be temporarily detrimental as there can be a nitrogen-robbing effect at first, causing chlorosis, possible fatality. Bark would have less risk than shredded wood.

The trick is recognizing/admitting if/when your pot is no longer providing optimal conditions and having the restraint to keep the watering can away from it until repotting is possible (for house plants.) And of course, trying a little differently next time to make your mix so it lasts an appropriate amount of time for a plants' repotting schedule. Tweaking the size/% of the chunks, or other alterations. As long as there are virtually no tiny particles of anything at the beginning, that's a good start, IMVHO/E.

This winter, I intend to compost a cubic yard or so of the bark, and see what I get.

At the link is an article about growers in Florida using 100% pure composted pine bark as container fill - I assume there must be some bigger chunks of bark in there for structure.

Here is a link that might be useful: link

At the link, they are using it for pepper plants for about 9 months tops. This also seems important, " Water and nutrients were applied several times a day with the duration of each irrigation event set to leach slightly at the end of the event."

Comparing the results of a cubic-yard pile over winter in CO to the stuff actually used for an operation like this in GA is a dubious comparison at best.

It's as much about the texture as size of chunks used. If already composted, the water-retentiveness has begun, making it more like 'dirt' than bark. It would serve a different function in a soil mix, again with a caveat against small pieces. If it's already crumbly, (like pieces of bark I encounter in my own compost pile,) I'd not use it in a pot at all. As 100% of a 'mix,' it's going to be extremely short-lived. I wouldn't try this (or 100% composted anything) with most 'regular' house plants, unless I wanted to repot them twice a year.

This only becomes an issue for me for the large containers that I use for temporary 'annual' displays. There is no way that I would or should fill those containers with my bark based potting medium.

I've used styrofoam packing peanuts for years. I began saving those mesh bags that onions, some potatoes, etc., come in and stuff them with the styrofoam. The bags keep the peanuts contained AND are reusable!

Roots love the peanuts....it will not get rancid or moldy or smelly, and will never get soggy. At the end of the season, I have to sever the massive root system from the mesh bags in order to toss the annuals and then soak the bags in a soapy water tub. A good, rough washing dislodges most of the roots......I hang them in the storage shed for the winter.

The styrofoam filler offers OXYGEN. If your potting mix is a conventional one, the roots will use the styrafoam as the growing medium....desperate for oxygen. If your growing medium is highly porous (which it should be), the plant roots will populate the upper layers of the large container, too.

Please remember that styrofoam does not decompose in our landfills. Try to choose mailorder vendors who don't use styrene foam as a packing material. Make your concerns known. If this material does come into your home......reuse it!

I'll compost the bark and see what I get - If it looks ok, I'll add some of it to the general, recycling container soil effort. It would be mixed in with plenty of perlite, pumice, and what ever other structural components make it from year to year.

I've used those styrofoam peanuts as well. Then slowly, I stopped getting stuff packed in the styrofoam kind, it was all the bio-degradable corn starch peanuts. That went on for years, and I'd just go dump them into the compost pile.

And then this past year, I received something or other with a several cubic feet of peanuts, which I assumed were corn starch, and so dumped them (in a stiff breeze) on the compost pile and they all blew all over the garden where they turned out to be styrofoam. :-(

This post was edited by david52 on Wed, Sep 18, 13 at 10:43

David, sorry that happened, but hilarious story!

Good stuff, Rhizo. I think the lines are being accidentally blurred here between seasonal outdoor pots and more permanent house plant pots.

There are packaging peanuts that are compostable, ie made of some kind of cornstarch base I think. These would really be a bad idea in a container. I had a bunch of containers left at this house with large chunks of styrofoam in the bottom, and all of it was really hard to extricate from the dead roots left by the plants the original owner had planted in them. I take the styrofoam ones I get to the packaging/mailing store, and they are happy to reuse them. Oops, now I see that david mentioned these peanuts already. Well, anyway. I have a wood stove and lots of bark from firewood, so I just use bark.

i've been using styrofoam pellets for years in outdoor containers and for indoor too. i then use coir matting to lay on the bottom and coming up the sides (thicker on bottom, thinner on sides) to form a kind of 'inner pot'. it prevents soil from dropping into pellets and also allows me to easily pull the rootball out without spilling soil all over. also the roots don't get stuck to clay. and i think coir matting on sides helps to aerate and air-prune the roots - i get no circling!
for some really strange shaped ceramic pots very wide on top and very narrow on the bottom i upturn small sturdy plastic pots and put them in 1-2 layers on top of each other and back-fill with pellets too if needed. then i can either put in a plastic liner pot or do a 'coir matting liner'

Wow, lot's of great ideas and experiences..

I have one I stumbled across today!!!

I have a gardenia planted in a coco basket and the chains broke...So the only way I could get it to stand was to rest in on a ceramic round pot with only a inch of old mulch in it..
The actual coco basket was not small enough to fit in the entire pot, just on top and half way in.

Well, when I took that coco basket out from the pot, I had TONS of pure white roots trying to reach for the mulch at the bottom of the ceramic pot, 6 inches down..

Those roots were basically growing in air trying to reach for the bottom...lol

Rhizo, talk about air root loving the oxygen between both pots in the space void of any mix....It was beautiful...So I put it back just the way it was..The plant is a very happy camper.

Mike

See "D":
{{gwi:5807}}

Empty soda bottles are good space taker uppers, as are bricks/rocks if you want more weight. Packing peanuts are a PITB, and don't offer anything an empty soda bottle doesn't offer, even bricks would be better than peanuts. Water tends to perch above layers like peastone or packing peanuts. And since packing peanuts have closed-cells, they don't hold water or nutrients, and roots can't penetrate beyond any imperfect (open) cells at the very surface of the particles. Soda bottles or bricks at the bottom of the pot take up space in the part of the pot most likely to be occupied by perched water. Essentially, they reduce the volume of soil occupying the PWT, and in doing so, they reduce the amount of perched water the container can hold. This means that air returns to the o/a soil mass much faster. Imagine how much less perched water the soil could hold if up to 90% of the shaded area in figure A above was taken up by bricks or empty soda bottles (90% less).

The PWT is always a fixed ht with any given medium, even if it perches atop a drainage layer. Anything you do to reduce the volume of soil in the PWT reduces the volume of perched water.

Al

Hi
i use styrofoam or occasionly use expanding foam cut into appropriate sizes with a layer of fiber glass screen . keeps the potting mix from sinking into the foam raises the mix, lightens the pot .When time to repot the mix is easily separated .. I use a lot of leca and crushed lava so weight and cost are important For the vegetable bed use
prunings from the yard though I skip the screen as it's an ongoing project and only needs to last a season. gary

We had an ample supply of fresh tomatoes as the plants responded favorably to my new idea of adding a portion of a half rotten log under the newly planted seedling. This allowed the roots of the plant to seek out the micronutrients that the original tree had accumulated during its lifetime of growing. The log, when it becomes rotten and decayed, turns spongy and like a sponge, it absorbs water, which in turn, is absorbed by the thirsty plant. Also less irrigation is required when the pieces of old, rotten log are added to the container.

I use medium from top to bottom due to the possibility of perched water tables. I've learned from my mistakes! :-)

But see Al's diagram above, jodik. With a smart shape of whatever's on the bottom, you can reduce the volume and effect of perched water, not increase it.