The vermiculite ends up compacting the soil, not letting it 'breathe', and the peat moss, except in smaller amounts, stays wet for a long time (even though the top might dry), so I'd use more perlite, skip the vermiculite and add a handful of small aquarium gravel for better drainage and aeration.

Personally, I prefer to use vermiculite in some mixes -- especially for plants that prefer a constantly moist medium. Some horticultural vermiculite has larger 'grains' that provide for more aeration. (The larger type might be called 'expanded' vermiculite, I can't remember.) However, I never go out of my way to search out the larger variety, I simply grab a bag of whatever is available. If vermiculite is used in proper ratio to other ingredients in your mix, it will not pose a threat to drainage/aeration.

If peat is dry/powdery to the touch, it's extremely important to moisten it thoroughly BEFORE incorporating it into your mix. I bought a large old collander at a garage sale specifically for this purpose. I pour very hot water over the peat, allow it to drain as it cools (it can retain heat for a long time) & squeeze out as much excess water as possible before adding other ingredients to it. It should be moist, not wet.

I also regularly use perlite. I don't want to be an alarmist, but I think we should all exercize caution when working with perlite. Perlite dust becomes airborne very easily & sort of lingers, hanging in the air. Take whatever measures necessary to avoid breathing the stuff.

Never pour perlite rapidly from the bag, but carefully measure out the amount you need. Better yet, to completely eliminate the dust, moisten the entire bag as soon as you open it. I clip a top corner & the diagonally opposite bottom corner off each bag, run water from my garden hose thru the top hole & allow it to drain out the bottom. Make the bottom hole small so you can regulate the exit flow with your fingers (keeping the perlite from flowing out too). I then transfer the moist perlite to a lidded container or a plastic bag where it remains moist (& dust free) indefinitely. Prolonged exposure to perlite dust has been shown to have a carcinogenic effect. The home gardener is probably at very little risk, but why take chances?

Short question, long answer. For a more concise (& probably more informative) reply, I've added a link.

Here is a link that might be useful: Soilless Potting Media Recipes

windeaux, show some data that perlite can be carcinogenic. I won't believe it until I see some proof.

I'm guessing that you are thinking of something else. (Like vermiculite.) BUT, will be happy to be educated. ;-) Especially since I use perlite all of the time.

Trace, it depends on the type of plants..my basic ingredients consist of black soil, peat, sand and perlite.
For tropical plants I add 1/4 of each..For succulent plants, I add more sand/perlite.
No beach sand, only builders bought at HD..Been using this mix for yrs..Toni
PS, I occassionally add vermiculite in tropicals..

But know that most of us have determined that a fast draining potting medium is the best option for healthy, care-free plants. That would eliminate the black soil stuff, and actually the sand, which can end up filling up the pore spaces in a container mix. Unless, of course, your sand particles are as large as fish aquarium gravel. Builder's sand is waaaay to small.

A terrific potting mix for a beginner would be half and half perlite and peat. It will look a bit different than what you are used to, but it allow you to feel confidant about your plants. It would be very difficult, for example, to over water your plants in this mix! You won't be troubled by root diseases or fungus gnats, either.

I add a few other things to my mix of peat and perlite (Turface MVP, pine bark fines, granite grit), but that's just fine tuning. The peat and perlite alone get the job done!

Good luck!

Rhizo, I've been using this mix over 20 yrs...the sand works fine, as does black soil..as long as it's mixed correctly there shouldn't be any problems..My plants never are bothered with fungus gnats...Every so often, in winter, spider mites appear, but after I spray them (non-insectides) mites are extinct.
This is the way I pot up my plants..everyone has their own methods..Toni

Perlite dust is apparently considered carcinogenic by the World Health Organization, though not OSHA. OSHA does have upper limits for exposure to perlite dust, though as best as I can tell that's because it can be irritating to skin, eyes, and respiratory tract, not because it causes cancer.

Perlite is also considered a hazardous substance by the state of Massachusetts (again, probably because of eye/skin irritation).

Probably not something the average hobbyist gardener would have to worry about, and I'm not worried about it personally, but it'd be something else entirely if your exposure is occupational, frequent, or exceptionally intense.

www.howred.com/GoodtempSafety.pdf

I am pretty familiar with what makes a good and what makes a bad soil, and I'm with Rhizo in asserting that a soil comprised of equal portions of sand, black soil (I have to guess this is topsoil or garden soil), peat, and perlite will compact, hold too little air, and too much water. It may be acceptable in some nursery situations where a quick turn-around of plant material is expected, but for containerized plants - I'd never suggest it.

There are actually measurable guidelines established that allow us to determine if a soil is appropriate for use in containers, so let's talk some percentages. The best container soils will have about 60-75% total porosity and will be able to retain that porosity for many, many waterings. Total porosity is the relationship between the amount of solids in a soil to the spaces that will hold both air and water. So, 60-75% of a good soil will either be filled with air or water when the soil is at container capacity. Container capacity is the condition of the soil after it has been fully saturated and has just stopped draining. Now, at container capacity, the best soils will have about 30-35% air in them. This means that when the soil is fully saturated it will be about 40% water, 30% air, and 30% solid particulates. This combination is probably very seldom (never?) found in an "out-of-the-bag" mix and if it is found, the mix will usually not retain its structure long enough to support the percentages for a grow season. It will certainly never be found in a mix that is 75% fine particulates like equal portions of sand, topsoil, perlite, and peat.

Because commercially bagged soils already break down quickly and compact, you should avoid amending container soils with things like sand, topsoil, and compost. All these ingredients serve only to fill valuable air spaces, increasing compaction, and reducing air volume/aeration.

If you make significant and sustainable aeration and drainage your primary focus when you build or choose your container soils, you can probably eliminate an extremely hi % of your growing problems, and I include insect infestation and attacks by pathogens (this includes root rot issues) among them.

Al

Al, I am not talking about outdoor topsoil/mulch, ect..when I say black soil, I'm refering to brands such as Hyponex, etc, that doesn't contain mediums such as peat, vermiculite, perlite. It's a black, heavier soil that's been around many yrs. I would not use an outdoor soil on indoor plants. In the 70's, when I first started growing plants, there weren't many indoor soils available..It was after experimenting I decided mixing up mediums was best for plants..As time went by, I came up with the black (indoor) soil, peat and sand. Toni

I would still vigorously try to discourage other forum readers from attempting to grow in the media you described. Sorry, but it invites problems. Nearly all bagged soils collapse too quickly & subsequently hold too much water and too little air. If you're using a bagged soil, you should amend with materials that individually provide structural stability and promote aeration, not sand and peat. Additional peat serves no purpose in a soil already likely comprised of up to 90% peat. It will soon break down to very fine particulates. Sand, while stable in composition, destroys aeration, unless it approaches 1/2 BB size or larger.

I can agree with the idea that mixing your own media can provide a far superior soil than "from a bag" mixes, but I'm afraid my choice of ingredients varies substantially from yours for the reasons I noted above.

My considered guess is that the soil you described would be less than 50% total porosity and exhibit about 20-25% air porosity at container capacity (when the soil is saturated). This can create problems for even the most skillful waterers - guaranteed.

I have advantage over you in that I have grown in soils similar to what you describe & found them lacking. After years of studying container soil physics & chemistry, I've learned that aeration is the key ingredient in selecting or building a container soil. I've several times offered to send you a bag of soil to try, so you could see the difference as well, but you decline & continue to defend a heavy soil that is certain to compact & collapse in containers.

Of course, it doesn't matter to me what you use for soils, but I'd have a guilty conscience if I didn't point out inherent problems with the blend of ingredients you listed and that a high % of growers will encounter soil related problems with a high % of plant material - especially any who are inclined to be heavy-handed with the water.

Al

If my doctor (or DENTIST!!) said that she did the same things for 20 years, I'd run as fast as I could out of her office!

The black soil you are using is sedge peat. Hyponex is famous for that. I cannot imagine a worse product for containerized plants, unless you are growing bog or swamp plants.

Can I butt in here for a moment? I realize I'm a nobody, and I've only been experimenting with more difficult/less common varieties of houseplants for a very few years. With limited success, I readily admit. Before that I grew lots of plants for 30 years (but they were only of the very common, foolhardy varieties; ie: pothos, philos, draceanas, spiders, etc). So bear with me, but doesn't obvious success carry any weight here? Toni has been growing a HUGE variety of houseplants since the 70s. Some real difficult ones, too. She would no longer be growing them at all if she wasn't having success, don't you think? I can honestly say that any question I have for her, I can count on an almost instant, knowledgeable answer. And I have yet to discover a mistake in her IDs (and I've emailed her quite a few!) Hyponex or black soil may not work for everyone, but its OBVIOUSLY working for her. Now, if she posted here all the time about killing plants left and right, I wouldn't put much weight in her comments. Not to say she doesn't lose one now and then, (admit it - everyone does) but the sheer number of plants she has, and have bloomed for her and thrived just blows me away. I'm sure lots of others here are equally impressed. Look at how devastated we were when she was gone! I, for one, will continue to follow her advise. Nothing speaks louder to me than success!

Randi

I've been growing (albeit only the very common varieties) houseplants for about 30 years, and only just in the last few years have I delved into some of the more uncommon/difficult growers here and there, but I know Toni has been growing a HUGE variety for OVER 30 years, and look at the success she's had. How many people have a sufficient green thumb to keep the variety of plants she has alive, much less healthy?

Toni is a VERY talented grower, no doubt. She would have to be to grow in that kind of heavy mix, and have it work for her. But, for the typical grower and lover of indoor plants, that potting medium would cause problems.

Just think how happy all of those plants would be in a planting medium that was porous instead of a bit mucky? lol They'd be doing the happy dance!

BTW, I've been growing for a zillion years, too. I'm always looking for improvements on what I've been doing and am never, ever hesitant to experiment with something that makes sense to me! Plants respond in fascinating ways to what we provide for them.

Well I decided that naything I repot....lol, I will use a good commercial mix, with some added perlite and vermiculite, some of them are in a straight commercial mix and they are doing fine, but for the new ones I will add perlite and vermiculite, and from what I have read, I will add a bit more perlite, as it seems to have more positive things about it than vermiculite. I think I will try rooting some cuttings in pure perlite as I have some in commercial mix and a few in vermiculite, I guess to each his own.

It sounds like everyone has found what works for them, so I am going to take a bit of advice from everyone and see what works for me....I still am not sure about the peat moss thought, I have a bag, but I am not sure what exactly it does, or if I should be adding some as well.

Tracy

I love the discussions on everyones diiferent mediums, I adore Toni's advice as well as Al's now looking back through posts.....They both have always offered great advice and expereinces, but again, what works for one might not work for the other, depends on your habits as well I think, as in watering anf fertilizing....etc.

Hi Tracy,

Just wanted to put my 2 cents in about using vermiculite. I know it's tough when you have a big bag of something and can't use it, but I would just ask you to think twice before using it in your planting medium. Vermiculite, peat, and perlite is a great mixture to use for rooting cuttings, but I wouldn't use it for a long term medium. You'd have to be really careful to avoid overwatering. For a plant that loves wet feet, I guess using vermiculite would be fine. Anyway, it's all up to you in the end!

Good luck,
Gabi

I also believe perlite can't be good for the lungs, whether its a carcinogen or not. I've tried to be careful, but when pouring it in a closed or nearly closed up room (like the bathroom) I have started coughing and had trouble breathing for nearly an hour afterward. Scared me. So I know that especially for certain sensitive people, perlite can't be the best for the lungs. I now go outside on a breezy day and pour it into the pots, being sure I stay upwind of the dust. Wetting it prior to using it is an excellent idea also.

Lots of really good suggestions and discussion. I think the peat/perlite/vermiculite is one of the Cornell mixes, which means to me it must have some good qualities. I used it for years. Don't like the way vermiculite breaks down in things I don't re-pot regularly, and don't usually use it anymore. I don't know about perlite being a carcinogen, but had a friend get pneumonia from inhaling it. Really important to be careful--wear a dust mask, or follow some of the previous suggestions. One really important thing I've learned in the many years I've been doing this, is that not only what I do may not work for you, but what I do may not work for ME when I move. Went through that a number of times. What worked in Nebraska where I lived before I moved here is almost guaranteed not to work here in south Louisiana. I will never consider myself an expert--just a student constantly learning!

trace, I like to root my cuttings in a 50/50 mix of perlite & vermiculite. For plants, I buy a good soilless mix, and if it seems heavy, or if I know from previous usage that it's heavy or has a lot of peat, I add some perlite. I add more perlite for plants that require more drainage, such as tropical hibiscus.

hey, what would you suggest for a very porous potting mixture (that won't become compact after watering) for succulents? i've visited several websites and they have all recommended a similar formula: 1/3 perlite/vermiculite + 1/3 peat moss + 1/3 loam. What do you all think? thanks everyone!

Hi Zestin,

You're asking a different question, that's usually best done on a separate thread.

But since you've asked, I don't think your suggestion is a good one. I grow mostly succulents & I try my best to avoid peat, stays too wet (also can become compact when dry, becoming too difficult to re-wet). Vermiculite is used for water rention. Given those two things, why would you even consider this mix good for succulents?

Fast draining is the opposite of water retentive, if that's what you're after, ditch the vermiculite & the peat altogether.

A much more appropriate mix for succulents would be 2/3 cactus & succulent mix (pereferably one w/out peat) & 1/3 perlite (or more), this will be fast draining & fine for succulents; it's more or less what I use for mine except that I use pumice in place of perlite.

Loam doesn't really belong in a container. Loam is garden soil. The actual definition of loam is any garden soil containing a certain percentage of sand, silt, clay, and organic matter.

I know I'll probably take a hit for this, but I'll stand firm on my assertion that the mix of equal parts of peat, black soil, sand, and perlite is a poor choice for houseplants - especially for inexperienced waterers. We can actually quantify what makes a good container soil, as noted above. Aeration is KEY in container soils and this mix WILL compact and WILL NOT hold enough air for an extremely high % of plants to ever grow at or even near their potential genetic vigor.

I'm the first to say that it doesn't matter what soils are actually made of, as long as they provide anchoring, nutrient and water-holding ability, and most importantly - they must hold an ample volume of air and allow gas exchange at the rootzone. The soil described above will lack aeration and adequate gas exchange.

That a particular person does something for a number of years with results that are acceptable, doesn't mean it should be adopted by others. Saying, "It works for me" is simply a statement and should not be regarded as a clarion call that others should follow blindly.

That's all I have to say, and it's just an opinion, but it's easily supported by science and practical experience, and can be corroborated by dozens, if not hundreds of folks I've helped with soil problems over the years. I'm not trying to stir the pot here, just trying to help folks see that there are better choices than the mix we're discussing. Use science, don't fight against it. (I wish someone famous would have said that so I could offer it as a quote & it would carry more weight) ;o)

A friend of mine, Joe Pye, comes to mind as I consider the reasoning of some. Joe Pye would get up every morning before work and bang his head against the wall. He always said it worked for him. One day he got tired of banging his head and decided to change, so he kissed his wife goodbye instead. Joe never did go back to banging his head. Moral: If your happy with how things are growing, please maintain the status quo, but at least allow there just might be a better way.

Al

I just read thru this whole thread and still feel like I've been left hanging...
The suspense is killing me.

We still don't know what ingredients make a good soil mix...
AL?

You can read here, an ongoing discussion about Container Soils, and if you wish to dig deeper, a little more here, about Soil Physics and how water behaves in containers.

Al

There's a very good ongoing subforum on www.bonsaisite.com - go to 'General discussions' forum first - lots of info. there.