LESS PERLITE = BETTER?

[cjk]

please show me anything anywhere with actual science behind it showing you can improve the drainage characteristics of a medium by adding large particulate matter.

The BB's in the pudding example illustrates this quite simply, yet the idea persists you can improve aeration by adding 25% perlite.

Perilte has no internal porosity. It does nothing but exclude both water and air.

my science includes years of growing with many different peat and perlite combinations. not only indoors but also in the retail nursery industry with native and drought tolerant plants that have to have the extra aeration and hate being overly tended to or "overwatered". the more perlite added to a peat mix or any soil, the more aeration, drainage, and overall soil porosity you will achieve. within my indoor growing experience, it has been obvious that roots respond positively to the extra aeration up to a certain point. obviously, you will have to water more. if you want to hear this from somewhere else i guess you take a look at the chart contained on page 3 of this study ...
http://www.perlite.org/perlite_info...ES OF PERLITE AND SPHAGNUM PEAT IN NORWAY.pdf

 

[supuradam]

my science includes years of growing with many different peat and perlite combinations. not only indoors but also in the retail nursery industry with native and drought tolerant plants that have to have the extra aeration and hate being overly tended to or "overwatered". the more perlite added to a peat mix or any soil, the more aeration, drainage, and overall soil porosity you will achieve. within my indoor growing experience, it has been obvious that roots respond positively to the extra aeration up to a certain point. obviously, you will have to water more. if you want to hear this from somewhere else i guess you take a look at the chart contained on page 3 of this study ...
http://www.perlite.org/perlite_info...ES OF PERLITE AND SPHAGNUM PEAT IN NORWAY.pdf

For one thing, I doubt few here grow in 75% peat.

 

[cjk]

For one thing, I doubt few here grow in 75% peat.

not sure what your point is??? actually, a lot of the most popular soilless mixes on this site such as pro mix or any of the sunshines are probably sitting at about 75% peat out of the bag. of course a lot of people are ammending them but not with other mediums (except possibly coco or composts), just organic additives such as ewc, kelp, guanos, etc. but these aren't really going to change soil consistency... there's a reason why almost every industrial ornamental grower use peat/perlite combinations in bedding plants, perennials, and hanging baskets. there's a reason why sunshine and pro mix are so popular...

 

[love2gro]

I thought air space comes from having many different sizes of materials in your mix, so that it all dont just compress together leaving no space for air?

 

[pinecone]

Mad has got me thinking about containers, how water behaves in them, and pros and cons of various drainage amendments, but (much to my disappointment) I'm not anywhere near figuring anything out for myself. When I find some time I want to use the approaches in the pdf and website below to quantify the properties of a few container mixes.

http://www.agf.gov.bc.ca/ornamentals/floriculture/aeration.pdf

http://oregonstate.edu/dept/nursery...etermining_container_physical_properties.html

Pine

 

[mad librettist]

LESS PERLITE = BETTER?

my science includes years of growing with many different peat and perlite combinations. not only indoors but also in the retail nursery industry with native and drought tolerant plants that have to have the extra aeration and hate being overly tended to or "overwatered". the more perlite added to a peat mix or any soil, the more aeration, drainage, and overall soil porosity you will achieve. within my indoor growing experience, it has been obvious that roots respond positively to the extra aeration up to a certain point. obviously, you will have to water more. if you want to hear this from somewhere else i guess you take a look at the chart contained on page 3 of this study ...
http://www.perlite.org/perlite_info...ES OF PERLITE AND SPHAGNUM PEAT IN NORWAY.pdf

that's not science, it's barely an anecdote.

the fact that adding even 50% perlite to a mix will not change drainage or aeration characteristics is directly observable fact. it's the laws of physics vs your experience here.

your success with perlite is readily explained by the fact that perlite excludes water, so total water retention for the planting is less, which takes less time to dry. but drainage and aeration characteristics of a peat mix do not change until you have close to 70% perlite.

the analogy is correct - adding 25% perlite to retentive soil is like adding 25% BB's to pudding. Yes, the pudding with BB's dries out faster because there is less water to start with, but the characteristics are the same.


as for sharp edges vs. round, that doesn't work if you have massive particles (perlite) mixed with tiny ones (peat). If all particles are the same size then yes, sharp means less compacted.

 

[h.h.]

Yet you use BB's as an analogy. You also assume the meshing of the peat with the perlite is 100%. We can use concrete as an analogy. A meshing of ultra fines, fines, and aggregate, it still has capillary action.
The problem with perlite, as I see it, is that it breaks down quickly, producing an abundance of ultra fines, emulating more and more your beloved BB's.It's good for one grow. It's main charm being that it can be commercially had. Somebody figured out a profitable way to package and sell it.
The answer lies in using a variety of stuff. I'm using a commercial mix now, but it contains rice hulls and small pieces of volcanic rock. Stuff that won't screw up the soil as it breaks down. Added some coconut shell, though that's a pain and it was limited. Bigger pieces are fine though. Roots like them with meat attached. Also a bit of char that was teaed up.Trying out some free packs of silica rocks. No perlite this round though. I was persuaded to use it and it did help what I was doing then. Well, being the waffling type, or what I prefer to think of, being open minded, I've been convinced to move beyond perlite.
I guess, don't knock it until you try it. I would have concerns over the DE breaking down and over time becoming muck in the soil, same as perlite. I guess the same as the silica rocks might. Silica is something I add anyway in which case it may be an advantage.

 

[cjk]

agree to disagree. try taking cuttings or starting seeds in "bb's" and then try taking cuttings or starting seeds in perlite and you'll see how they compare, the characteristics are not the same ...

 

[mad librettist]

agree to disagree. try taking cuttings or starting seeds in "bb's" and then try taking cuttings or starting seeds in perlite and you'll see how they compare, the characteristics are not the same ...

dear jesus, I know these are hard concepts but this is ridiculous!

let me try again.

BB's and perlite have a few things in common, but to make it easier on everyone, let's assume the bb's are the same size as perlite. Better now?

BB same size as perlite: no internal porosity, large particle size means no water is held between particles. Other than bulk density and shape, they have the same characteristics, and therefore identical perched water table heights.



so far so good.

no wait, make it better.

say we add PERLITE to pudding. Chocolate pudding, not the instant kind (details, details). Does adding 25% PERLITE to pudding change the drainage or aeration characteristics of the pudding? NO!

Say we add 70% PERLITE to pudding. Same pudding. Do we now have different drainage and aeration qualities, as in the actual properties of the medium? YES!




As for rooting in perlite, try calcined DE, it's way better, faster, and easier. BB's will work just fine as well depending on what they are made of. There is absolutely nothing about perlite that makes it better than BB's the same size, other than an irregular shape.

Yet you use BB's as an analogy. You also assume the meshing of the peat with the perlite is 100%. We can use concrete as an analogy. A meshing of ultra fines, fines, and aggregate, it still has capillary action.

let's get more specific. Peat with even 50% perlite has the SAME capillary action as PURE PEAT. Capillary action and its relatives, cohesion and adhesion, are part of the forces working against gravity (drainage) in a mix. When forces pulling or holding water up are stronger than the force of gravity pulling down, the result is a perched water table.


We know for a fact that perlite has no internal porosity, so we know it does not hold air nor water.


The benefits of adding perlite to a mix do not come from increased drainage, air porosity, or water porosity. Perlite helps by simply taking up space and denying water access to that space. Therefore your mix dries out faster and, to you, seems "better drained and aerated"


If anyone wants to see me eat some words and crow, SHOW me the different perched water table heights in a clear container with pure peat and one with 50/50 peat/perlite. I am making an EXPLICIT GUARANTEE that the two media will have EXACTLY the same drainage characteristics.

 

[cjk]

wow, it's not that i don't understand what you're saying. it's that I disagree... perlite is porous and filled with minute cavities and pores. if water isn't contained throughout the cavities and pores because of evaporation, being used up by the plant, drawn out because of the capillary action of peat, or simply draining through when watering then air is pulled into the cavities. it's physics!

 

[mad librettist]

If not for the fact I made the same arguments as you not that long ago, and got taken to school by someone who knows their shit for real, I might let that go.

But perlite as an example of porosity? Maybe according to the perlite institute.

Why don't you do some science? Let us know how much water a dry pint of your perlite absorbs, and we'll compare it to some other items? From what I can tell though, you aren't clear on the different forces at work, or even what a perched water table is. Follow the link in my sig, there's a simple video.

Even perlite holds some water, which means we can technically say it is porous. But it's relative to other things before us. I have about a half dozen different drainage amendments in the house. Perlite is the least porous. In other words, it isn't very porous.


So I can tell you part of the answer is that perlite fucking sucks on porosity. That is why people who don't need to worry about bulk density and who know what they are doing don't use perlite. They use calcined clay, DE, volcanic rocks like pumice and scoria, etc... because those items are far superior in terms of air and water porosity. What does that mean? It means having cake and eating it too. It means that compared to a perlite mix, your roots get more water, more air, more surface area to colonize.



People who know, are worried about bulk density (costs $ to move mass), and who need a good drainage/aeration component for very large amounts of media are now using rice hulls. I saw an entire container's worth the other day outside a nursery. That's a lot of pallets. Each pallet held just one big bag of rice hulls.

Do they use perlite? No fucking way, that's for consumers. Ironically, they were not equipped to sell me a bag of rice hulls, but they had plenty of perlite for sale. It seems the average gardener is not well educated, and would rather pay 5 times as much for popcorn made from glass (using fossil fuels for heat btw) that has real half the value of the useless part of rice and barely lasts longer.

At least rice hulls break down into silicon your plants can use to defend themselves.

But even so, whether you use perlite, DE, scoria, pumice, soil perfector, calcined attapulgite, fuller's earth, or pozzolana, the drainage and aeration characteristics of any peat based medium are the same as the drainage and aeration characteristics of peat alone. This has been measured and repeated. Adding large particles to peat does not achieve a "halfway between the two". If you want to improve those characteristics, you have to increase the particle size all around, as Spurr has done with his pine bark based mix. The only other alternatives are 1)a wick, or 2)del with it until roots fully colonize the medium.

 

[cjk]

If not for the fact I made the same arguments as you not that long ago, and got taken to school by someone who knows their shit for real, I might let that go.

But perlite as an example of porosity? Maybe according to the perlite institute.

Why don't you do some science? Let us know how much water a dry pint of your perlite absorbs, and we'll compare it to some other items?


I can tell you the answer is that perlite fucking sucks on porosity. That is why people who don't need to worry about bulk density and who know what they are doing don't use perlite.

good note to end on. it was fun!

 

[mad librettist]

wait til you get to the edits...


btw the reason it gets back to perched water table height is that if drainage characteristics are identical, so is the PWT height. If they are different, then the PWT height can't be the same.


even changing container sizes does nothing to alter PWT height:

(is anyone guessing one reason I like big containers?)

 

[cjk]

If not for the fact I made the same arguments as you not that long ago, and got taken to school by someone who knows their shit for real, I might let that go.

But perlite as an example of porosity? Maybe according to the perlite institute.

Why don't you do some science? Let us know how much water a dry pint of your perlite absorbs, and we'll compare it to some other items? From what I can tell though, you aren't clear on the different forces at work, or even what a perched water table is. Follow the link in my sig, there's a simple video.

Even perlite holds some water, which means we can technically say it is porous. But it's relative to other things before us. I have about a half dozen different drainage amendments in the house. Perlite is the least porous. In other words, it isn't very porous.


So I can tell you part of the answer is that perlite fucking sucks on porosity. That is why people who don't need to worry about bulk density and who know what they are doing don't use perlite. They use calcined clay, DE, volcanic rocks like pumice and scoria, etc... because those items are far superior in terms of air and water porosity. What does that mean? It means having cake and eating it too. It means that compared to a perlite mix, your roots get more water, more air, more surface area to colonize.



People who know, are worried about bulk density (costs $ to move mass), and who need a good drainage/aeration component for very large amounts of media are now using rice hulls. I saw an entire container's worth the other day outside a nursery. That's a lot of pallets. Each pallet held just one big bag of rice hulls.

Do they use perlite? No fucking way, that's for consumers. Ironically, they were not equipped to sell me a bag of rice hulls, but they had plenty of perlite for sale. It seems the average gardener is not well educated, and would rather pay 5 times as much for popcorn made from glass (using fossil fuels for heat btw) that has real half the value of the useless part of rice and barely lasts longer.

At least rice hulls break down into silicon your plants can use to defend themselves.

[]But even so, whether you use perlite, DE, scoria, pumice, soil perfector, calcined attapulgite, fuller's earth, or pozzolana, the drainage and aeration characteristics of any peat based medium are the same as the drainage and aeration characteristics of peat alone. This has been measured and repeated. Adding large particles to peat does not achieve a "halfway between the two". If you want to improve those characteristics, you have to increase the particle size all around, as Spurr has done with his pine bark based mix. The only other alternatives are 1)a wick, or 2)del with it until roots fully colonize the medium.[]

oh shit! actually i can't end on that now that this was said^. i'm in the retail and wholesale nursery business everyday. i also tour some of the largest growing facilities in my state to look at product and most all large scale growers are still using perlite. a lot of have tried rice hulls and went back to perlite as long as consistent perlite can be found.

 

[cjk]

wait til you get to the edits...

haha!!

 

[mad librettist]

lol and the place I just visisted switched back to rice hulls.. after switching back.


I noticed scoria, pumice, calcined DE, attapulgite, and any other number of actually good drainage amendments are left off your relative table. Also missing: durability (how do these qualities hold up over time).

rice hulls:low durability (not meant to be permanent)
perlite: worse than useless as it breaks down into smaller pieces that add to water holding
calcined DE, scoria, etc...: no head scratching here.

 

[cjk]

...We know for a fact that perlite has no internal porosity, so we know it does not hold air nor water..]

yea well our discussion wasn't over durability. you said this ^ which set me off. also, comparing perlite to bb's just doesn't do it for me. the reason perlite is a good cutting medium is capillary action. cloning in bb's you would have to have a constant drip and variable size bb's becuase of compaction and density to have any success. comparing pudding to peat as well ... ouch! peat is porous in itself which allows perlite to aerate it further. pudding on the otherhand is not

 

[mad librettist]

pudding is not porous? So if I set up a pudding barrier, liquid won't get in through any holes?

If I filled up a pot with bb's, and poured a bit of pudding on, would liquid drain out? If I used smaller bb's, would less liquid drain out? (yes on both counts - what sticks to the bb's stays behind)


ok, I admit Al's example is not perfect, but it teaches us that whether or not perlite is "aerating" your mix is not based merely on the relative properties of each component, but the proportions. The mix itself will have drainage characteristics based on whatever makes up the majority of particles. It's simply a property of the medium as a whole.

Get what I'm saying? DE, perlite, pozzolana, it doesn't matter. If it's only 25% of your mix it isn't influencing your drainage characteristics.

You want to take the properties of each, put them together, and get a compromise. That is what we expect because we are taught bullshit about how a medium is put together, by perlite salesmen. But media in containers don't behave that way.

Listen, I grow bog plants in 50/50 peat/perlite. It drains the same as LC mix. I never really looked until I 2ndtry (spurr) rocked my world a year ago. So now i can just switch to long fibered sphagnum straight up and ditch the "cp mix" as each plant needs a repot.


This knowledge has also freed me. Because at first, I was really disappointed. You see, it's impossible to make perfect organic container mixes. You need compost to make the system work, and that really mucks up a perfect container medium. So I just go for amendments that last long and hold lots of water (turface, DE), and I look for alternative ways to drain my soil. Option one as I said is a wick, but even better is a living wick - to wit, a living mulch.

 

[cjk]

durability isn't exactly an issue for most commercial growers as the products they sell come with the media there grown in ... in other words, they don't recycle it or need it to be recyclable. durability isn't an issue with me either as i always have a fresh batch of soilless media availible for the next starts. actually, the perlite makes my plants so root bound, i can't reuse my media!! LOL!

 

[cjk]

pudding is not porous? So if I set up a pudding barrier, liquid won't get in throug any holes?

not like it would with peat...