Is The Use of Vermiculite/Perlite Antiquated?

[ookiimata]

Any New Growers Who Glance At This Post Without Reading It Word For Word, Note That The Below Quotes Are Not A Suggested Nor Common Practice.

I was browsing the Mandala Seed site, and found something kind of interesting in their Soil Guide. It basically goes against everything I've ever learned concerning drainage additives, so I'm just curious what you guys think. Hopefully this hasn't been discussed before. I searched but it came back with every thread that had the word "vermiculite" in it so there were tons. In the following post, I use perlite/vermiculite interchangeably for simplicities sake.

Quoting their site:

Horticultural grade potting soil is perfectly mixed for the best air-water ratio. Adding more non-nutritive substances depletes the water retention capacity of the soil, it unnecessarily "stretches" the soil and reduces the total amount of nutrients available to the plant, and it creates dry pockets in the container.

Adding a large amount of perlite/vermiculite (some growers add as much as 25%!) is a completely outdated practice from 30-40 years ago when there was only a very small selection of horticultural potting soil available for non-commercial gardeners. It is one of the unfortunate harmful practices in cannabis cultivation that many still cling to although they do not understand the reason or consequences.

Especially harmful is to fill the bottom of the container with coarse materials such as expanded clay pebbles. This is where most roots grow down looking for water and nutrients! If they reach a dry and sterile layer of substrate the delicate root hairs shrivel, valuable space is lost where the plant requires rich soil that stores moisture and minerals.

If you are planting outdoor and your soil is too compact a modest addition of perlite/vermiculite or sand helps to increase drainage. Humus, such as from compost, is the best additive because it also provides many microorganisms and nutrients to the soil mix.

So this is aimed specifically at growing cannabis, and they're saying that perlite usage is antiquated. And several books on cannabis cultivation I've read specifically advise to use a layer of perlite at the bottom of the container. In that regard, I've both used and not used the bottom layer, but never paid attention if it made a difference. A couple times I just forgot to put it in there and never thought about it after to see if it affected anything. They do seem to suggest expanded clay balls rather than vermiculite in that instance, although I'm still hesitant if they mean perlite/vermiculite as well.

The only added bennies they recommend are rock dust and Endomycorrhiza, and they specifically say not to use guano. I feel this should be mentioned to put the claim about perlite in context, as it could possibly reflect on every claim they make regarding soil.

So should we not be adding perlite? Or, if we are, should be only be adding it at a ratio consistent to the quantity of bennies added, and not the overall soil quantity? So, say, if you add a total of 2qts of combined bennies to 3.5cu ft of soil, you'd add 1/3 of 2qts instead of 1/3 of 3.5cu ft.

Just curious, as the claims made on their site are new to me. I'm aware their plants are particularly fert sensitive, but their claims seem to be aimed to cannabis cultivation in general, and not at their plants specifically.

 

[Kaiser Puff]

It may be true that people add too much perlite to their soil, but perlite/vermiculite has it's place in soiless hydro so it's not altogether antiquated by any means...

 

[SSHZ]

I think they are stating that by adding too much perlite to soiless mixes, it drains off too quickly and can dry out the roots if not watched carefully. I agree with their comments, basically the more organic items you add to the soil, the healthier and livelier soil, with better moisture holding capabilities. Add perlite, most of us do- just don't over do it cause too much is bad. Put what you want in the bottom of your pots- just don't make it deep. A couple inches at most.

 

[Seamaiden]

If perhaps your goal is to go greener than mined products (perlite & vermiculite are mined and processed, not so green) then look into substituting rice hulls for perlite. They don't quite behave like it, when they're wet they feel like shrimp shells, but they are light-weight, MUCH more cost-effective than perlite.

Time for some much-detested math: I can get double the cubic feet for a fraction of the price of perlite, i.e. 4'cu bale of perlite is usually $22, 8'cu bale of rice hulls are usually around $6.

So, perlite averages $5.50/cubic foot, whereas rice hulls, which are being produced no matter what as an agricultural waste product, average $0.75/cubic foot. That is a HUGE difference in cost, just huge.

If you're interested, go to feed suppliers and ask for rice hulls packaged as animal bedding. If you go the ag supplier route they usually want you to buy in bulk (by the ton).

 

[antimatter]

I sorta agree with the above, if a gardener was to add a lot of perlite and not able to keep up with the watering than it would be a problem. The bottom 2 inch thing I don't really understand because my plants often sit in alot of runoff with no problems even though everything ive read said that they would get to soggy at the bottom.

 

[ent]

Well just about any organic potting soil you buy these days (roots organic, fox farms) are soooo damn hot I basically use the perlite to cut it. New bag of FFoF run off will test out at around 4.5-5.0 EC. Also after 10 weeks or so the soil will become very compacted. The perlite and air pockets it creates help so the plants do not become water logged or over watered. I've found growing without perlite or vermiculite in organic soil to be very difficult.

It also helps with the soil drying out completely, which is important with organic soil.

 

[Seamaiden]

I'm using a combination of rice hulls and coco, both for the above reasons.

 

[ibTheMan]

If your use n big buckets 7 to 10 gallon even with coco you need a good amount of perlite, you should have 10 to 20% run off every time you water, so with the extra perlite you get good drainage without waterloging them. IMO

 

[ookiimata]

Good info all around.

IB: I've always done the 10-20% drain off as well. Always thought it was the rule of thumb when it came to watering.

Seamaiden: I'm really interested in the rice hulls. Your description of them as shrimp shells really helped me visualize what they are and get a good grasp on them. So if you combine them with coco, what is your ratio of hulls to coco? And what percentage of your overall mix does the hull/coco combo comprise?


I pulled out Soma's organic growing book last night, and he does use a small percentage of perlite in his soil mix. He uses 11 gallons earth worm castings, 33 gallons black peat, 11 gallons potting soil, 33 gallons Bio Bizz Light Mix, then 10 liters of perlite. He also uses guano, maerl (apparently the same thing [or very similar] as greensand), and DCM organic fertilizer in his mix at 4.4lbs each. But he puts a layer of expanded clay at the bottom, then a layer of chicken wire and black felt, then the soil. So his recipe definitely seems to have some very stark contradictions with Mandala's.

 

[Blaze]

I dislike both perlite and vermiculite. I would tend to agree with the statement that they are outdate as there are cheaper, more effective additives one can use to increase drainage. The main reasons I do not like them is that perlite always floats to the top in a soil mix and vermiculite sinks to the bottom. Also, over time they become pulverized and ground into dust, and this dust can be quite hazardous to inhale. They also provides no nutrients or anything else to the soil, so it really is just filler. Rice hulls, coco, lava rocks and contractor sand are all much better alternatives, and cheaper too.

Also the theory of using a layer of perlite (Or anything else) at the bottom of a container to increase drainage is BS. The pressure differential actually prevents the pot from being able to drain well. Just filling your pots with your soil or soil-less mix with no layer at the bottom actually gives you better drainage.

 

[Seamaiden]

Here's something I noticed when my new transplants all got fed last night--they not only drain more quickly, the coco is disturbed less (these *are* new transplants after all), and they seem to drain better, retaining less weight than the perlite pots yet, not drying out terribly.

Since this is all new stuff, I'll have to update as I go.

iB, added the hulls in a more "by feel" manner, I'd have to say that I didn't use a whole lot, maybe 1'cu, give or take, uncompressed volumetric measure, that was added to a 5kg bale of expanded Botanicare coco.

Blaze, I'll be seeing you in a day or so, yeah? I only have a little bit of that Mendo Purps cross you gifted me trimmed up and ready to share, unfortunately, but you'll be able to see and sample it. If I should bring cuts of it for you, let me know, I've got a couple that I made for you just in case. Just started sampling the BMS cross, while not as tasty, she doesn't put me to sleep the way the other stuff does, better for daytime smoke.

 

[Blaze]

A cut or two would be great =)

Curious to see what pheno of the BMS cross you ended up with too. I enjoyed mine quite a bit - very unique smell, flavor and appearance. I'll be brining some of it this weekend.

 

[Hylife]

I grow in a 75%coco/25%perlite mix theres really no way to go without it because the coco would never drain if I didn't add it. Do rice hulls work with coco as well?

 

[Seamaiden]

Yes, they work, they just feel weird on your hands. I don't know where you got the idea that coco by itself won't drain. It will drain just fine.

 

[ookiimata]

I'm going to do a couple pots in a micro grow cab, so I figured I'd use soil the first run for simplicity/avoid having to fit hydro gear in the cab. Went around to every nursery in town but one and none had even heard of coco. The local feed store closed down a couple years ago when the owners retired, so I couldn't go there to ask for rice hulls (nor alfalfa, which I want). None had guano nor kelp either. So after that disappointing day I just ended up buying some perlite and using it in the soil mix I'm cooking. I still want to figure out a way to get rice hulls locally, though.

Thanks for all the info, guys and gals.

 

[bastard_x]

Any New Growers Who Glance At This Post Without Reading It Word For Word, Note That The Below Quotes Are Not A Suggested Nor Common Practice.

I was browsing the Mandala Seed site, and found something kind of interesting in their Soil Guide. It basically goes against everything I've ever learned concerning drainage additives, so I'm just curious what you guys think. Hopefully this hasn't been discussed before. I searched but it came back with every thread that had the word "vermiculite" in it so there were tons. In the following post, I use perlite/vermiculite interchangeably for simplicities sake.

Quoting their site:



So this is aimed specifically at growing cannabis, and they're saying that perlite usage is antiquated. And several books on cannabis cultivation I've read specifically advise to use a layer of perlite at the bottom of the container. In that regard, I've both used and not used the bottom layer, but never paid attention if it made a difference. A couple times I just forgot to put it in there and never thought about it after to see if it affected anything. They do seem to suggest expanded clay balls rather than vermiculite in that instance, although I'm still hesitant if they mean perlite/vermiculite as well.

The only added bennies they recommend are rock dust and Endomycorrhiza, and they specifically say not to use guano. I feel this should be mentioned to put the claim about perlite in context, as it could possibly reflect on every claim they make regarding soil.

So should we not be adding perlite? Or, if we are, should be only be adding it at a ratio consistent to the quantity of bennies added, and not the overall soil quantity? So, say, if you add a total of 2qts of combined bennies to 3.5cu ft of soil, you'd add 1/3 of 2qts instead of 1/3 of 3.5cu ft.

Just curious, as the claims made on their site are new to me. I'm aware their plants are particularly fert sensitive, but their claims seem to be aimed to cannabis cultivation in general, and not at their plants specifically.

I think too many assumptions have been made while reading this. you are trying to make it sound like hydroton , pearlite, and vermiculite are all the same. they are very different and all serve thier own purpose (not all are necessarily made for cannabis growing) .

hydroton is inert has no nute value . works well with hydro setups where as soils will clog pumps and not drain well. While draining well it also absorbs and retians small amounts of moisture that will evaporate off in a few hours.

vermiculite is not traditionally used to for cannabis growing its inert and has no nutrient value it also retains water very well but holds moisture much longer than hydroton . Its basically like a lot of little bacteria free dry sponges when fresh out of the bag.

Pearlite is a crystaline substance that is very pourus , it has thousands of little nooks and crannys for the water to go and be retained . Think of it like cups of water waiting for the roots to go and sip. Pearlite can retain water for a few days and the more you use the more water it can store .

The reasoning for lining the bottom of a pot with something coarse like hydroton gravel or even a course pearlite Is so that the soil is not washed out of the drainage holes at the bottom of the pot during watering , vermiculite would not serve this purpose because the granules are to fine
so chose the one that better suits your needs for a certian application

one final point i would like to make is that if organic marerial is soaking such as mulch or coco and not allowed to drain air would not contact the roots in that organic material. Thus causing root rot and mold to form on the organic material. If the part of the pot that is soaking is filled with an inert material such as hydroton or gravel or even pearlite it would be less likely to mold .So lets go back to the image of roots sipping thier drinks from the nooks and crannys in the more coarse substrate. Now if i was a root thats right where i would want to be .

 

[LightDep530]

I do not think that using an amendment such as perlite is antiquated but it is becoming rare and during peak season we experience perlite shortages around cali. As far as he nitrogen (guano) goes, I think Mandala strains are low feeders because of the Afghani heritage but 95% of the growers I know seriously amend bagged soil mixes. In a perfect world your soil biology would create all the nitrogen you need.

I have found that some kind of amendment is helpful for getting the soil to drain and dry out quicker. It all depends on your setup and climate too. I grow in big container 30-200 gallons and I like to be able to water every other day if not every day. I found that my mostly coco based soil mixture even with added perlite did not dry quick enough last year. I like the rice hulls, I think if you can get mostly composted rice hulls that would be idea.

Horticultural Pumice is also being used now. Vital Earth Manna Mix is a popular soil mix that has pumice in it, Roots does too I think.

 

[PipeCarver]

A few moments later..................................... old dated post

I'm looking into adding more Vermiculite to my soil during summer grows and up pops the Farm giving me answers