Vermiculite vs. Perlite

For gardening uses, what's the difference?

Vermiculite helps with water retention. Perlite helps with drainage and aeration of roots.

Thanks, I got the right one!

FWIW, both bags said drainage and areation. Strange.

etnredclay - I just looked at my bag of vermiculite and it did say helps with drainage and aeration. The next line says it helps with moisture retention. As you said - strange!

I've been looking into ammendments for clay and Vermiculite seems to be one of them. I found this interesting, seems it is one of those highly porous materials:
http://en.wikipedia.org/wiki/Vermiculite

And this on Perlite which is also highly porous but mainly made up of silicon dioxide whereas Vermiculite is mainly clay based:
http://en.wikipedia.org/wiki/Perlite

I believe that one tends to hold water like a sponge and the other does not so the pores tend to provide aeration. I'm new to this so not really sure.

I came across what seems to be an excellent article on growing tomatoes and the author highly suggested Fafard 3B commercial potting mix. I wondered what was in it and recently came across this page that lists the contents, note that it has both Vermiculite and Perlite:
http://www.griffins.com/products/product_info.asp?pl=SOILMD&pn=65-1548

The author also highly suggested pine fines which I've been unable to find. He obtained excellent results with both the Fafard straight and 50/50 mixed with pine bark fines.
At least two nurseries that I've been to say they always use Fafard mixes.

Does water really pentrate INTO Perlite? I didn't think it did. I thoguht Perlite was just a lightweight empty spot in the soil, that cuased less water retntion by displacing peat that would otherwise have held more water.

I like bark. I buy the cleanest coarsest "bark mulch" that I can, or "small pine bark NUGGETS" which seem to be much cleaner. Anything I found at Home Depot was dirty logyard waste, with powder, sticks, wood shavings and plain dirt along with some bark. Lowes "bark nuggets" were clean and inepxensive.

ONCE I found bark SHREDS and loved them, but they cost $7-8 for 2 cubic feet, whereas HD trash is $3.50, and good bark nuggets are $4.25.

Persoanlly, I have terrible luck with peat. It holds excessive water, I have not been able to cure myself of over-watering. NOT a good combo!

PeteB7,
When I first started using vermiculite, about 1953, I was told or somehow thought I learned that vermiculite was puffed mica, made by rapidly heating mica until it rapidly expanded. I had never heard of mica as being made from clay.

Interesting.

Paul

Hi Paul,
I'm not really sure exactly how it is made or the different ways it might be made. I have read that it is made from mica also and was going to say that the mention of clay in the wikipedia link was wrong. Then I read this that mentions Vermiculite clay:
http://adsabs.harvard.edu/abs/1969CoMP...24..136B

And this claiming that Vermiculite resembles mica:
http://www.dupreminerals.com/en/vermiculite/introduction

It is stated here that it is a micaceous mineral:
http://www.mineralszone.com/minerals/vermiculite.html

I'm not a materials expert but it seems that it is mined compound with the following chemical formula:
(Mg,Fe++,Al)3(Al,Si)4O10(OH)2·4(H2O)

I don't know if there are clays primarily made up of this compound but that is the only way I can see the claim that it is fired from clay being correct. Does anyone know more about Vermiculite?

This message was edited Aug 29, 2012 9:52 PM

I know that "Turface" and some other things (SOILMatrix ) are made from expanded clay or shale. High tmeperatures puff it up and make it porous enough to absorb and hold water.

"produced by expanding and vitrifying select shales, clays and slates in a rotary kiln."
Expanded Shale, Clay and Slate Institute
www.escsi.org

I wish they combine stuff like this with rock wool into tiny engineered shapes like saddles or interlocking spirals .. or porous tubes, I-beams or pretzles. It would be great for keeping potting mixes or clay soils from collapsing.

I don't know about Vermiculite.

ive seen that "turface" expanded clay..goes by few names..guess whoever manufactures it..
ive thought of trying it.. for my purposes ..would be on the slightly costly side.. like thats stopped me
from trying other soil ammendments..LOL
i use ALOT of perlite.. this season..i went thru.. 10 -- 4cf big bags..and its all gone now..
i dont have a need for vermiculite..i use my own compost..and composted leaves ..also coco coir..
so i dont have need for vermiculite.. i do need the porus addition to my soil mixes though.. both in my
gardens..and potted up plants..
i have been adding lava chips..also composted bark chips..
been thinking of trying cork chips too..
i "think" brian (brians botanicals) uses shipping peanuts in some of his mixes.. im sure small one..
if brian reads here..hope he'll say ya/nay...
i buy some good local compost that has alot of composted bark chips..i like it..

>> composted bark chips..

Cool. I haven't tried composting it first. What does that do, make it more porous? More hydrophilic?

I've thought of beating or compressing big chunks to soften or break them up: like hammering with a 3-pound hammer. Really, I would like to reduce thick "chunks" to long thin "shreds".

I wonder if bark will expand or "pop" like popcorn if I soak it and then microwave it?

lol..i can just see u rickcorey..out in backyard.. beating the *$($(*($# out of chunks of wood..
lol
you sound like someone i would get along with...:)
my neighbours think im nuts with all the compost i use/make.. that is until they need some for
their gardening..then..different story.. :)
the composted bark i buy has had nitrogen added to help break it down.. wood chips are a big drain
on nitrogen if just added to soil.. they have begun to decompose..size.. less than 1 inch..few shreds maybe
1 and half.. they keep my tropicals beds nice and fluffy..
i do think i need to add more perlite next yr.. with more coco coir..
this summer was tough on everything.. nothing died..but many of my EE's didnt get HUGE like they
usually do.. im blaming the weather.. :)

Anyone with the word "nut:" in their name must be a kindred spirit.

Whack! Whack!
"What are you doing?"
"Pounding bark."
Whack! Whack!

They must already know I'm crazy, but most of them are nice about it.

I have some raised beds, and then improved the drainage further by digging a fairly deep trench / sunken walkway between them. When I'm down in the trench you can only see my upper torso sticking above the raised bed walls. It probably looks like Invasion of the Mole People.

But it means I can plant and weed with hardly any bending or stooping!

>> ... wood chips are a big drain on nitrogen if just added to soil..

I agree. But I think that bark breaks down mush slower than wood does, for similar-size chunks. And I think that bark ahs a little more N than wood does, so it is somewhat less of a N-leach than wood. And wood or bark on the surface, as MULCH, is safer than burying them raw.

>> the composted bark i buy has had nitrogen added to help break it down..

That does sound smart - why make harder for the roots of the plants you WANT to grow?
I've heard that "straw bale gardeners" do the same thing: pour high-N fertilizer into bales of straw so it decomposes rapidly as tomato roots grow into it.

I finally found a bag of Urea (46-0-0) as the cheapest possible nitrogen source (until someone loans me a dump truck I can fill with biosolids from the plant in Everett). But you have to spread urea VERY thinly to keep from burning roots, like dissolve it and spread it that way. I've been told "less than 2 pounds per 1,000 square feet per application", and that's 0.9 grams per square foot. P_lus it is very soluble so too much would wash right out.

I think vermiculite helps with aeration because the individual grains of vermiculite, while they are individually moisture retentive, allow surplus water to pass through and leave intersitces for air... hence both water retentive and drainage and aeration.
I use fine vermiculite to avoid (totally) damping off of seedlings. I used to have huge loss of seedlings to damping off but since using ½-1" of vermiculite as the growing medium over the compost, I have not lost a single seedling to the infection.
My big beef is that garden centres tend to massively overcharge for small volumes of vermiculite. Typically one pays (in the UK) £1 per litre - £5 for a 5 litre sack.
However, I found a horticultural supplier who was happy to sell me a 100 litre sack for £13.90 and he took a good profit!!!
Since, if kept dry vermiculite lasts effectively forever, the 100 litre sack is a great idea.

lol..ya..im a nut.. just ask any of my neighbours..:)
but..im a happy camper.. so... :)
i learn so much from u all..and your experimentations in gardening...
some work for me..others dont..or because some things arent readily available
here..cost is a factor.. sometimes..LOL i think we all stretch when its something
we just HAVE to have..or try...
i agree cinemike with garden centers over horticulture suppliers..on price..
the big bags of perlite i do buy..are bigger than any of the big box stores carry..and
the bigger bags are less than the smaller bags.. go figure..

Pine bark chips, shreds or fine nuggets are also good for preventing damping off. Mixed into the seedling mix, they give great drainage and aeration. The less-moist surface of the mix gave me zero damping off since the year I strarted using bark in the mix. (I always over-water, I can't seem to stop myself from over-watering.)

Now I also sprinkle a few coarser bark shreds on top of the mix, where they dry out just minutes after I top-water. The seedling stem is surrounded by dry bark chips or shreds almost all the time and never rots.

I suspect that Vermiculite prevents damping-off by being sterile. Bark prevents it by assuring a dry, aerated surface.


>> the bigger bags are less than the smaller bags.. go figure..

I went to a farm coop store that has a little Yuppie retail outlet attached to a big warehouse.

For $9 in the retail outlet I could buy a pretty-pretty color-printed Zip-lock reclosable bag with 2 quarts of #2 chicken grit (crushed washed granite). Probably 25 cents for the grit and $8.75 for the pretty bag. Why have a Zipl-Loc bag for crushed granite? To keep it "fresh"?

For $10 plus driving around the corner of the warehouse, I got a 25 KILO bag of the exact same thing. And they put it in my turnk for me. Something like 15 times as much for 10% more money.


Instead of buying Perlite OR Vermiculite, I now buy pine bark (mulch or nuggets). Adding plenty of those to a mix (like 2-10 parts bark per 1 part of peaty mix) makes it much more airy and MUCH cheaper. $4.20 for 2 cubic feet is something like 28 cents per gallon.

Cheap bark "mulch" is often FILTHY, lots of soil/dirt, wood and powdered bark. It looks like they threw logyard waste over the muddy spots where they were working, and then drove over it with trucks. Plus, it is often damp and fermenting (not in a good way). That was my Home Depot experience 2-3 times in a row, ($3.50 / 2 cubic feet).

One very classy nearby nursery sold "Medium Bark Mulch" called "Beauty Bark" that was great - clean, dry and mostly long shreds, though there was still a good bit of powder and fine bark fibers to screen out. $7.50 for 2 cubic feet. Twice the price, but 10 times the quality.


Then I discovered "bark NUGGETS" at Lowes, for $4.20 / 2 cubic feet. It was even cleaner than the classy nursery's MULCH, and the medium grade had almot NO powder or fiber. ("Medium" was too coarse for seedling mix and almost too coarse for potting mix).

The "Fine" grade of "nuggets" had just a little powder, so I screened that out with 1/4" hardware cloth. (I could still have used some of what went through the 1/4" mesh, for seedling mix, but I might just turn that fine stuff under some raised beds.)

Probably screening this with 1/8" mesh would give a good Perlite substitute, but I like bigger chuinks than "coarse" Perlite. "Coarse" Perlite is smaller than "fine" bark nuggets.

The only disadvantage of nuggets is that they are "chunks" instead of long thin "shreds". Nuggets are shaped like hockey pucks or hamburger patties, in sizes from 1/8" up to "large nuggets" with long dimensions up to several inches. I would only use "Large" nuggets for top-dress mulch. But they are great for that, like over drip irrigation tubing.

Rick,
thanks for all the ideas for pine bark mulch - I have 3 bags just waiting to be used right now. I had only used it as top dressing for a couple of crepe myrtles (for looks) and for blueberries (for acid mulch). I never worried about screening out the fine dusty part - what harm does that do? Also thanks for reminding me to get a big bag of vermiculite at the farm supply store - btw, what in the world does a farmer do with vermiculite?

I'll look at Lowe's pine bark nuggets to see how it compares to pine bark mulch. I wonder if my NC Lowes stocks a different pine bark mulch from your WA Lowes store.

My neighbor made friends with a guy who trims and cuts down trees - now the guy will drop off, free, a large heap of shredded tree parts. ( I'm too lazy to move a huge pile of shredded tree parts around my yard.)

Paul

i think you have great soil addition ideas rick!
my tropicals..and especially EE's need really good drainage..
but also some moisture retention..
lol..sounds contradictory..huh.. but really isnt..
ive kicked around idea or fern tree shreds,cork chips,and theres a
new zealand bark (orchid growers use)
the NZ bark is way to much $$$ for amount i would need..
i'll go hit Lowes and get try some of these bark nuggests..
for me i think the larger ones is what i'd need..

>> I'll look at Lowe's pine bark nuggets to see how it compares to pine bark mulch. I wonder if my NC Lowes stocks a different pine bark mulch from your WA Lowes store.

I bet you're right. Probably bark supplier's costs are 80-90% transportation.

>> now the guy will drop off, free, a large heap of shredded tree parts.

Drool! Drool! Envy!!

>> I never worried about screening out the fine dusty part - what harm does that do?

Outdoors, probably none. I would expect the fines to wash down into the soil and improve the soil. MAYBE if the mulch was mostly fines, weed seeds would grow in it instead of drying out. I like to put big clean chunks on top where they dry out and protec t the soil from evaoprating, but mix the fines right into the soil.

In potting mixes or seedling trays, too much fine stuff defeats my purpose of FAST-DRAINING, WELL-AERATED mix, even when I over-water from the top.

>> I never worried about screening out the fine dusty part - what harm does that do?

Start seedlings in trays?

I have bought a bag or two of "orchid bark", but you might as well sbhred $1 bills into the mix. They look just like Lowes "Beauty Bark" large pine nuggets, thoguh one such bag had some wood shreds in it that I had to pick olut. If the oprchids are re3ally fussy, you might want to rinse the bark first, just to clean it up a bit.

When you first open the bag, shoved your nose right down int here and smell it. If it was damp in a mostly-sealed bag, it might have fermented anaerobically and left some alchols, acids and whatever fermentation products. If it smells nasty, leave the bag in a dry place, open wide to air out, and/or rinse the chunks well before using.

>> need really good drainage..

Well, bark won;t hold much water unless you have shreds or very small chips. So I would say to use some big chunks to get huge air gaps, then add just a LITTLE peaty stuff or fine-pshredded bark, so that the gaps are not filled, but the peat does hold some water.
but also some moisture retention

I''ve been getting ACE Hardware 'pine bark mulch" and addding it generously to potting mix such as Scotts or Miracle Gro. I LUV the bark. It's in very small chips. I sift it some to find enough bigger chips for my orchid. She LUVS that. New roots all over the place.

Their Nugget stuff is all bigger. Average cheap Shredded hardwood is very dirty and rotten already usually, more like compost than chunks.

The 3.69 bag of pine bark mulch is the same size as the $11 bag of potting mix- dollar stretcher.

Bought Fafard once and it was very coarse, nice and bark-ey.

thanks to all!! i think i avoid many of my "ideas" and costly.. LOL if i
read here and what u all are using with sucess..
:)
im off to home depot/lowes tomorrow for some stuff..
i'll hit the garden centers while there..

>> It's in very small chips. I sift it some to find enough bigger chips for my orchid.
>> Their Nugget stuff is all bigger.

Check out Lowes' smallest bark nuggets. Those might be big enough for tyour pet orchid, if they are like the bark nuggets in my area.

I've heard good things about Fafard (and Pro-Mix).

>> Average cheap Shredded hardwood is very dirty and rotten already usually, more like compost than chunks.

Maybe I should be more polite about Home Depot, someitmes they give away empty pots and web trays.
Instead of calling it "filthy logyard waste", I should call it "composted bark mix.