# Why Does Potting Soil Have Styrofoam In It?
**URL:** https://boards.straightdope.com/t/why-does-potting-soil-have-styrofoam-in-it/59890
**Category:** Factual Questions
**Created:** [March 28, 2001, 10:23pm UTC](https://boards.straightdope.com/t/why-does-potting-soil-have-styrofoam-in-it/59890 "2001-03-28T22:23:40Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@DougC](https://boards.straightdope.com/u/DougC)
#### Post date: [March 28, 2001, 10:23pm UTC](https://boards.straightdope.com/t/why-does-potting-soil-have-styrofoam-in-it/59890/1 "2001-03-28T22:23:40Z")
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- As long as I’ve recognized it as such, I have wondered this. -And we don’t need to get picky about it not being Real Actual Styrofoam, but it definitely does seem to be some sort of white plastic foam pellets. We might theorize that because it is porous, it helps trap and hold water but I know from using a water-filtration vacuum cleaner that the stuff is very bouyant; if it absorbs liquids, it don’t absorb much. - MC
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### Author:  [@scratch1300](https://boards.straightdope.com/u/scratch1300)
#### Post date: [March 28, 2001, 10:42pm UTC](https://boards.straightdope.com/t/why-does-potting-soil-have-styrofoam-in-it/59890/2 "2001-03-28T22:42:06Z")
It’s [perlite](http://www.perlite.net/). It’s including in potting soil for aeration and to retain moisture.
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### Author:  [@Chas.E](https://boards.straightdope.com/u/Chas.E)
#### Post date: [March 28, 2001, 11:52pm UTC](https://boards.straightdope.com/t/why-does-potting-soil-have-styrofoam-in-it/59890/3 "2001-03-28T23:52:33Z")
There are several additives used in potting soil, I know well because it was my afterschool job for a few years mixing potting soil. The good soil mixtures use vermiculite or perlite. It’s supposed to “aerate” the soil by preventing it from sticking together. The cheap places grind up styrofoam which as far as I’m concerned is just pollution.
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### Author:  [@Harmonious\_Discord](https://boards.straightdope.com/u/Harmonious_Discord)
#### Post date: [March 29, 2001, 2:42am UTC](https://boards.straightdope.com/t/why-does-potting-soil-have-styrofoam-in-it/59890/4 "2001-03-29T02:42:18Z")
The polystrene balls will never break down in you life time. It’s used to keep the soil mixture loose. Buy soil that has vermiculate, perilite, and ground moss.
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### Author:  [@Homer](https://boards.straightdope.com/u/Homer)
#### Post date: [March 29, 2001, 5:17am UTC](https://boards.straightdope.com/t/why-does-potting-soil-have-styrofoam-in-it/59890/5 "2001-03-29T05:17:00Z")
Hasn’t vermiculite been withdrawn from the market because it’s been shown to cause cancer in pets?
–Tim
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### Author:  [@Shiva](https://boards.straightdope.com/u/Shiva)
#### Post date: [March 29, 2001, 2:15pm UTC](https://boards.straightdope.com/t/why-does-potting-soil-have-styrofoam-in-it/59890/6 "2001-03-29T14:15:02Z")
> [@](#):
>
> \*Originally posted by Homer \*
> \*\*Hasn’t vermiculite been withdrawn from the market because it’s been shown to cause cancer in pets?
>
> –Tim \*\*
Nope. I’m still selling it by the truckload. Literally.
Boy, do I ever have a glamorous job.
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### Author:  [@malden](https://boards.straightdope.com/u/malden)
#### Post date: [March 29, 2001, 2:29pm UTC](https://boards.straightdope.com/t/why-does-potting-soil-have-styrofoam-in-it/59890/7 "2001-03-29T14:29:58Z")
[hijack]
There _is_ a concern (still being investigated) that vermiculite contains asbestos, and therefore should not be used indoors, i.e., as insulation. The EPA is investigating possible massive asbestos exposure at a vermiculite mine in Montana.
[/hijack]
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### Author:  [@Homer](https://boards.straightdope.com/u/Homer)
#### Post date: [March 30, 2001, 12:47am UTC](https://boards.straightdope.com/t/why-does-potting-soil-have-styrofoam-in-it/59890/8 "2001-03-30T00:47:32Z")
Excellent. I need vermiculite for a little mycology experiment next month, and I had been told I was unable to get it any longer. Good to know it’s still available.
–Tim