I just put some cuttings in sifted perlite. While sifting, probably 30% is dust to 1/8". So out of my 3 cubic ft bag, i'll have approx 1 ft of these small particles. is there any use for this? or should I just toss it?

Don't breathe it!  You could get cancer!  Couldn't hurt to dig it in or rototill it in to the ground for some aeration, but do not breathe it!!

Suzi

Yep, I'd agree with others. Mix this in with your other potting soils. The fine particles are ok for everything OTHER than new cuttings in small cups.

I'd throw it out.  It will add nothing of benefit.

I do what Bob does and toss it! Potting soil already had too many fine air clogging particles as it is. The dust will only add to the problem.

Hate having to throw this stuff out.  Very wasteful.  Have 3-5 buckets of it.  Any other uses?

I usually use miracle gro perlite and sift through it a bit and its mostly dust. Usually for a few days afterwards I'm nonstop coughing. I'd have to agree with suzi, be careful with the dust.

Hypertuffa is the only thing that comes to my mind, or other concrete mixes.

I too am looking for ways to re-use it.

Hypertuffa is sort of scary to me.  Like, would I mold a dying lady onto my hillside and cover her with milk and moss?  YIKES!!  There is such a forum on GW.

Suzi

I'm not convinced there is any real use for perlite at all, dust or large pieces or in between.  As far as I can tell the only thing it does well is take up space. 

I've used it plenty over the years thinking that I should, because it's in potting mix, etc, but now I really question its value or purpose.  

Oh Wow  somebody else had coughing fits with this stuff.   Thought it was just me.   Joyce

Rob, it is needed to take up space. It allows the roots to move around more freely in pots. It is also needed to make the pots much lighter than they otherwise would be with gravel or any other medium. (Useful when carrying the pots in and out of storage) It also helps to create a free draining soil that does not hold too much water. I'm not saying it's the Holy Grail but it does many things.

My chickens pick out the perlite from my potted plants. They pick up the sifted perlite I've spilled as well. Not sure if it is harmful to them, they eat small stones and dirt all day long. Maybe it helps with digestion.

Mike in Hanover, VA

I would suggest using a mask when you work with perlite, especially if it is indoors.  Repeated exposure over a long period of time has been associated with lung disease of various types:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4002636/

I'm with Rob on Perlite.  If I want a low weight additive that aids drainage I go with biochar chunks.  They don't decompose, are very low density, and they also can act like sponges to hold extra water. 

How about pumice ? Is it a good substitute?

I've never worn a mask when working with perlite. Have never felt any ill effects before but will take the advice and wear a mask from now on. Thank you.

It looks like this thread has taken a turn from what to do with sifted perlite to the usefulness of the stuff. I never knew there was any negative sentiment toward using perlite and quite frankly can't find a reason for knocking a product that helps my plants to thrive. Perlite does have some water retention properties but its real usefulness to help reduce soil compaction and provide aeration is undeniable. Fat perlite rocks!

First off, sorry for hijacking the thread.

I would think that a discussion of the merits of this stuff or lack thereof would be welcomed by anyone who uses it.  Particularly someone who goes to the trouble to sift it and then has the dust leftover and is wondering what to do with it. 

I never said it's a bad product or harms the plants in any way.  I had used it myself for several years.  I just am not convinced it's worth the additional expense. 

So I am just going to go through it analytically, and I welcome anyone who has any thoughts that might increase my understanding or change my opinion.

What does the phrase, "reduce soil compaction and provide aeration" mean, specifically? 

How does potting mix become compacted and how does this product reduce it?  I can only think of 3 possible ways that potting mix can become compacted. 
1.  The roots will keep growing through it and eventually they will cause it to be compacted because their mass will increase faster than the mass of the potting mix decreases due to decomposition.  The volume and mass (and therefore density) of the perlite will remain constant, provided it doesn't crumble into dust.  The rest of the mix, roots included, will increase in mass but volume will remain constant, therefore density (and presumably "compation" whatever that is) will increase, since D = M/V.  I can't see how perlite will do anything to combat this process. 
2.  The weight of the mix itself will cause the mix to be compacted.  Maybe perlite reduces this because it reduces the weight of the mix.  But at the same time it reduces the media available for the roots.  For example, if I have 5-1-1 mix, that is 1/7th perlite.  Let's assume that perlite weighs nothing.  So now the pot is 1/7th lighter.  But it also has 1/7th less area for the roots to grow in.  Couldn't I have just used a 6 gallon pot instead of a 7 gallon pot to achieve the same impact?
3.  Over time the particles will decay into smaller pieces and therefore become more dense as the air pockets are filled with matter.  This process will march along regardless of the presence of perlite. 

How does it provide aeration?  I can tell you that for sure a bucket of pine fines has plenty of air pockets already.  Now maybe in those peat based nursery mixes, like pro mix, etc, the perlite does provide some additional air exchange.  But in a primarily pine bark mix, this is not necessary.

So my conclusion is that it's expensive stuff that takes up space. 

BTW, I'm offering a tire air replacement service.  The stuff I use is 79% nitrogen and therefore it provides great tire inflation!

I use perlite to root cuttings.  Once they go in to pots they don't get any more perlite.

Rob,

I can't discuss the scientific merits of Perlite, but when starting out in container gardening it is probably a good idea to follow a recipe, like 5-1-1.

With that said, I stopped using it except on cuttings, and will probably one day find a replacement for cuttings as well (sand has not worked as well).

I stopped because; one, it is costly, second, I like to re-compost old potting soil and it looked awlful floating out, and lastly, I quit adding peat to my mixes and came to a similar conclusion as you, that pine bark fines are all that is needed un-sifted.

I know, blasphemy, but my figs haven't seemed to care and watering schedule is unchanged.   

I screen my perlite on the lawn. So the dust goes on the lawn. There is always a breeze, I stay up wind and don't breath when the wind shifts. Expanded rock dust in the lungs is bad juju.

Yes this thread has taken a weird turn. I think the answer is there is no use for sifted perlite.

My mix is 50% ProMix HP 50% Pine Bark Fines. The HP stands for High Porosity. The extra perlite does everything I said above and allows for faster and more even water coverage. If your mix is not porous the water will travel to the edges of the pot and go down the sides. All of the perlite allows the soil to remain more friable and allows water to drain straight down into the soil. Even to the center of the root ball.

In addition I add pine bark fines to also aid in the same way. Consider this, loose topsoil (like newly rhototilled) is easy to shovel. Compacted soil that has sat for a long time is hard to dig into. No mater what material you use, the idea is to increase the friability, drainage, and porosity.

BTW I did buy a 4' tall perlite bag for about $20. I would not call that expensive. The plan was to make my own mix using Perlite, Peat Moss, and Pine Bark Fines. I have about 2-300 / 10-15 gal pots to make this year.