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Container Soils - Water Movement and Retention IV

Bay City, MI(Zone 6a)

Continued from:

I am reposting this information mainly out of consideration for those who find it takes a considerable amount of time to load because of its length. It has garnered much more attention than I ever imagined it would, and has been great fun - a wonderful catalyst in the forging of new friendships and in increasing my list of acquaintances with growing interests similar to mine. Since there are many questions about soils appropriate for use in containers, I'll post basic mix recipes later, in case any would like to try the soil. It will follow the information. This thread is not about recipes, though they are widely discussed, it is about concepts and a way of approaching gardening in containers that varies from what we might consider current convention. I'll let the success stories and enthusiasm in the previous postings, and likely this one, speak for themselves.

Before we get started, I'd like to mention that I wrote a reply and posted it to a thread recently, and I think it is well worth considering. It not only sets a minimum standard for what constitutes a 'GOOD' soil, but also points to the fact that not all growers look at container soils from the same perspective, which is why growers so often disagree on what makes a 'good' soil. I hope you find it thought provoking:

Is Soil X a 'Good' Soil?

I think any discussion on this topic must largely center around the word "GOOD", and we can broaden the term 'good' so it also includes 'quality' or 'suitable', as in "Is soil X a quality or suitable soil?"

How do we determine if soil A or soil B is a good soil? and before we do that, we'd better decide if we are going to look at it from the plant's perspective or from the grower's perspective, because often there is a considerable amount of conflict to be found in the overlap - so much so that one can often be mutually exclusive of the other.

We can imagine that grower A might not be happy or satisfied unless knows he is squeezing every bit of potential from his plants, and grower Z might not be happy or content unless he can water his plants before leaving on a 2-week jaunt, and still have a weeks worth of not having to water when he returns. Everyone else is somewhere between A and Z; with B, D, F, H, J, L, N, P, R, T, V, X, and Y either unaware of how much difference soil choice can make, or they understand but don't care.

I said all that to illustrate the large measure of futility in trying to establish any sort of standard as to what makes a good soil from the individual grower's perspective; but let's change our focus from the pointless to the possible.

We're only interested in the comparative degrees of 'good' and 'better' here. It would be presumptive to label any soil "best". 'Best I've found' or 'best I've used' CAN sometimes be useful for comparative purposes, but that's a very subjective judgment. Let's tackle 'good', then move on to 'better', and finally see what we can do about qualifying these descriptors so they can apply to all growers.

I would like to think that everyone would prefer to use a soil that can be described as 'good' from the plant's perspective. How do we determine what a plant wants? Surprisingly, we can use %s established by truly scientific studies that are widely accepted in the greenhouse and nursery trades to determine if a soil is good or not good - from the plant's perspective, that is. Rather than use confusing numbers that mean nothing to the hobby grower, I can suggest that our standard for a good soil should be, at a minimum, that you can water that soil properly. That means, that at any time during the growth cycle, you can water your plantings to beyond the point of saturation (so excess water is draining from the pot) without the fear of root rot or compromised root function or metabolism due to (take your pick) too much water or too little air in the root zone.

I think it's very reasonable to withhold the comparative basic descriptor, 'GOOD', from soils that can't be watered properly without compromising root function, or worse, suffering one of the fungaluglies that cause root rot. I also think anyone wishing to make the case from the plant's perspective that a soil that can't be watered to beyond saturation w/o compromising root health can be called 'good', is fighting on the UP side logic hill.

So I contend that 'good' soils are soils we can water correctly; that is, we can flush the soil when we water without concern for compromising root health/function/metabolism. If you ask yourself, "Can I water correctly if I use this soil?" and the answer is 'NO' ... it's not a good soil ... for the reasons stated above.

Can you water correctly using most of the bagged soils readily available? 'NO', I don't think I need to point to a conclusion.

What about 'BETTER'? Can we determine what might make a better soil? Yes, we can. If we start with a soil that meets the minimum standard of 'good', and improve either the physical and/or chemical properties of that soil, or make it last longer, then we have 'better'. Even if we cannot agree on how low we wish to set the bar for what constitutes 'good', we should be able to agree that any soil that reduces excess water retention, increases aeration, ensures increased potential for optimal root health, and lasts longer than soils that only meet some one's individual and arbitrary standard of 'good', is a 'better' soil.

All the plants we grow, unless grown from seed, have the genetic potential to be beautiful specimens. It's easy to say, and easy to see the absolute truth in the idea that if you give a plant everything it wants it will flourish and grow; after all, plants are programmed to grow just that way. Our growing skills are defined by our ability to give plants what they want. The better we are at it, the better our plants will grow. But we all know it's not that easy. Lifetimes are spent in careful study, trying to determine just exactly what it is that plants want and need to make them grow best.

Since this is a soil discussion, let's see what the plant wants from its soil. The plant wants a soil in which we have endeavored to provide in available form, all the essential nutrients, in the ratio in at which the plant uses them, and at a concentration high enough to prevent deficiencies yet low enough to make it easy to take up water (and the nutrients dissolved in the water). First and foremost, though, the plant wants a container soil that is evenly damp, never wet or soggy. Giving a plant what it wants, to flourish and grow, doesn't include a soil that is half saturated for a week before aeration returns to the entire soil mass, even if you only water in small sips. Plants might do 'ok' in some soils, but to actually flourish, like they are genetically programmed to do, they would need to be unencumbered by wet, soggy soils.

We become better growers by improving our ability to reduce the effects of limiting factors, or by eliminating those limiting factors entirely; in other words, by clearing out those influences that stand in the way of the plant reaching its genetic potential. Even if we are able to make every other factor that influences plant growth/vitality absolutely perfect, it could not make up for a substandard soil. For a plant to grow to its genetic potential, every factor has to be perfect, including the soil. Of course, we'll never manage to get to that point, but the good news is that as we get closer and closer, our plants get better and better; and hopefully, we'll get more from our growing experience.

In my travels, I've discovered it almost always ends up being that one little factor that we willingly or unwittingly overlooked that limits us in our abilities, and our plants in their potential.

Food for thought:
A 2-bit plant in a $10 soil has a future full of potential, where a $10 plant in a 2-bit soil has only a future filled with limitations. ~ Al

Container Soils - Water Movement & Retention

As container gardeners, our first priority should be to ensure the soils we use are adequately aerated for the life of the planting, or in the case of perennial material (trees, shrubs, garden perennials), from repot to repot. Soil aeration/drainage is the most important consideration in any container planting. Soils are the foundation that all container plantings are built on, and aeration is the very cornerstone of that foundation. Since aeration and drainage are inversely linked to soil particle size, it makes good sense to try to find and use soils or primary components with particles larger than peat/compost/coir. Durability and stability of soil components so they contribute to the retention of soil structure for extended periods is also extremely important. Pine and some other types of conifer bark fit the bill nicely, but I'll talk more about various components later.

What I will write also hits pretty hard against the futility in using a drainage layer of coarse materials in attempt to improve drainage. It just doesn't work. All it does is reduce the total volume of soil available for root colonization. A wick can be employed to remove water from the saturated layer of soil at the container bottom, but a drainage layer is not effective. A wick can be made to work in reverse of the self-watering pots widely being discussed on this forum now.

Consider this if you will:

Container soils are all about structure, and particle size plays the primary role in determining whether a soil is suited or unsuited to the application. Soil fills only a few needs in container culture. Among them are: Anchorage - a place for roots to extend, securing the plant and preventing it from toppling. Nutrient Retention - it must retain a nutrient supply in available form sufficient to sustain plant systems. Gas Exchange - it must be amply porous to allow air to move through the root system and gasses that are the by-product of decomposition to escape. Water - it must retain water enough in liquid and/or vapor form to sustain plants between waterings. Air - it must contain a volume of air sufficient to ensure that root function/metabolism/growth is not impaired. This is extremely important and the primary reason that heavy, water-retentive soils are so limiting in their affect. Most plants can be grown without soil as long as we can provide air, nutrients, and water, (witness hydroponics). Here, I will concentrate primarily on the movement and retention of water in container soil(s).

There are two forces that cause water to move through soil - one is gravity, the other capillary action. Gravity needs little explanation, but for this writing I would like to note: Gravitational flow potential (GFP) is greater for water at the top of the container than it is for water at the bottom. I'll return to that later.

Capillarity is a function of the natural forces of adhesion and cohesion. Adhesion is water's tendency to stick to solid objects like soil particles and the sides of the pot. Cohesion is the tendency for water to stick to itself. Cohesion is why we often find water in droplet form - because cohesion is at times stronger than adhesion; in other words, water's bond to itself can be stronger than the bond to the object it might be in contact with; cohesion is what makes water form drops. Capillary action is in evidence when we dip a paper towel in water. The water will soak into the towel and rise several inches above the surface of the water. It will not drain back into the source, and it will stop rising when the GFP equals the capillary attraction of the fibers in the paper.

There will be a naturally occurring "perched water table" (PWT) in containers when soil particulate size is under about .100 (just under 1/8) inch. Perched water is water that occupies a layer of soil at the bottom of containers or above coarse drainage layers that tends to remain saturated & will not drain from the portion of the pot it occupies. It can evaporate or be used by the plant, but physical forces will not allow it to drain. It is there because the capillary pull of the soil at some point will surpass the GFP; therefore, the water does not drain, it is said to be 'perched'. The smaller the size of the particles in a soil, the greater the height of the PWT. Perched water can be tightly held in heavy (comprised of small particles) soils where it perches (think of a bird on a perch) just above the container bottom where it will not drain; or, it can perch in a layer of heavy soil on top of a coarse drainage layer, where it will not drain.

Imagine that we have five cylinders of varying heights, shapes, and diameters, each with drain holes. If we fill them all with the same soil mix, then saturate the soil, the PWT will be exactly the same height in each container. This saturated area of the container is where roots initially seldom penetrate & where root problems frequently begin due to a lack of aeration and the production of noxious gasses. Water and nutrient uptake are also compromised by lack of air in the root zone. Keeping in mind the fact that the PWT height is dependent on soil particle size and has nothing to do with height or shape of the container, we can draw the conclusion that: If using a soil that supports perched water, tall growing containers will always have a higher percentage of unsaturated soil than squat containers when using the same soil mix. The reason: The level of the PWT will be the same in each container, with the taller container providing more usable, air holding soil above the PWT. From this, we could make a good case that taller containers are easier to grow in.

A given volume of large soil particles has less overall surface area when compared to the same volume of small particles and therefore less overall adhesive attraction to water. So, in soils with large particles, GFP more readily overcomes capillary attraction. They simply drain better and hold more air. We all know this, but the reason, often unclear, is that the height of the PWT is lower in coarse soils than in fine soils. The key to good drainage is size and uniformity of soil particles. Mixing large particles with small is often very ineffective because the smaller particles fit between the large, increasing surface area which increases the capillary attraction and thus the water holding potential. An illustrative question: How much perlite do we need to add to pudding to make it drain well?

I already stated I hold as true that the grower's soil choice when establishing a planting for the long term is the most important decision he/she will make. There is no question that the roots are the heart of the plant, and plant vitality is inextricably linked in a hard lock-up with root vitality. In order to get the best from your plants, you absolutely must have happy roots.

If you start with a water-retentive medium, you cannot effectively amend it to improve aeration or drainage characteristics by adding larger particulates. Sand, perlite, Turface, calcined DE ...... none of them will work effectively. To visualize why sand and perlite can't change drainage/aeration, think of how well a pot full of BBs would drain (perlite); then think of how poorly a pot full of pudding would drain (bagged soil). Even mixing the pudding and perlite/BBs together 1:1 in a third pot yields a mix that retains the drainage characteristics and PWT height of the pudding. It's only after the perlite become the largest fraction of the mix (60-75%) that drainage & PWT height begins to improve. At that point, you're growing in perlite amended with a little potting soil.

You cannot add coarse material to fine material and improve drainage or the ht of the PWT. Use the same example as above & replace the pudding with play sand or peat moss or a peat-based potting soil - same results. The benefit in adding perlite to heavy soils doesn't come from the fact that they drain better. The fine peat or pudding particles simply 'fill in' around the perlite, so drainage & the ht of the PWT remains the same. All perlite does in heavy soils is occupy space that would otherwise be full of water. Perlite simply reduces the amount of water a soil is capable of holding because it is not internally porous. IOW - all it does is take up space. That can be a considerable benefit, but it makes more sense to approach the problem from an angle that also allows us to increase the aeration AND durability of the soil. That is where Pine bark comes in, and I will get to that soon.

If you want to profit from a soil that offers superior drainage and aeration, you need to start with an ingredient as the basis for your soils that already HAVE those properties, by ensuring that the soil is primarily comprised of particles much larger than those in peat/compost/coir/sand/topsoil, which is why the recipes I suggest as starting points all direct readers to START with the foremost fraction of the soil being large particles, to ensure excellent aeration. From there, if you choose, you can add an appropriate volume of finer particles to increase water retention. You do not have that option with a soil that is already extremely water-retentive right out of the bag.

I fully understand that many are happy with the results they get when using commercially prepared soils, and I'm not trying to get anyone to change anything. My intent is to make sure that those who are having trouble with issues related to soil, understand why the issues occur, that there are options, and what they are.

We have seen that adding a coarse drainage layer at the container bottom does not improve drainage. It does though, reduce the volume of soil required to fill a container, making the container lighter. When we employ a drainage layer in an attempt to improve drainage, what we are actually doing is moving the level of the PWT higher in the pot. This simply reduces the volume of soil available for roots to colonize. Containers with uniform soil particle size from top of container to bottom will yield better and more uniform drainage and have a lower PWT than containers using the same soil with added drainage layers.

The coarser the drainage layer, the more detrimental to drainage it is because water is more (for lack of a better scientific word) reluctant to make the downward transition because the capillary pull of the soil above the drainage layer is stronger than the GFP. The reason for this is there is far more surface area on soil particles for water to be attracted to in the soil above the drainage layer than there is in the drainage layer, so the water perches. I know this goes against what most have thought to be true, but the principle is scientifically sound, and experiments have shown it as so. Many nurserymen employ the pot-in-pot or the pot-in-trench method of growing to capitalize on the science.

If you discover you need to increase drainage, you can simply insert an absorbent wick into a drainage hole & allow it to extend from the saturated soil in the container to a few inches below the bottom of the pot, or allow it to contact soil below the container where the earth acts as a giant wick and will absorb all or most of the perched water in the container, in most cases. Eliminating the PWT has much the same effect as providing your plants much more soil to grow in, as well as allowing more, much needed air in the root zone.

In simple terms: Plants that expire because of drainage problems either die of thirst because the roots have rotted and can no longer take up water, or they suffer/die because there is insufficient air at the root zone to insure normal root function, so water/nutrient uptake and root metabolism become seriously impaired.

To confirm the existence of the PWT and how effective a wick is at removing it, try this experiment: Fill a soft drink cup nearly full of garden soil. Add enough water to fill to the top, being sure all soil is saturated. Punch a drain hole in the bottom of the cup and allow the water to drain. When drainage has stopped, insert a wick into the drain hole . Take note of how much additional water drains. Even touching the soil with a toothpick through the drain hole will cause substantial additional water to drain. The water that drains is water that occupied the PWT. A greatly simplified explanation of what occurs is: The wick or toothpick "fools" the water into thinking the pot is deeper than it is, so water begins to move downward seeking the "new" bottom of the pot, pulling the rest of the water in the PWT along with it. If there is interest, there are other simple and interesting experiments you can perform to confirm the existence of a PWT in container soils. I can expand later in the thread.

I always remain cognizant of these physical principles whenever I build a soil. I have not used a commercially prepared soil in many years, preferring to build a soil or amend one of my 2 basic mixes to suit individual plantings. I keep many ingredients at the ready for building soils, but the basic building process usually starts with conifer bark and perlite. Sphagnum peat plays a secondary role in my container soils because it breaks down too quickly to suit me, and when it does, it impedes drainage and reduces aeration. Size matters. Partially composted conifer bark fines (pine is easiest to find and least expensive) works best in the following recipes, followed by uncomposted bark in the smaller than 3/8" range.

Bark fines of pine, fir or hemlock, are excellent as the primary component of your soils. The lignin contained in bark keeps it rigid and the rigidity provides air-holding pockets in the root zone far longer than peat or compost mixes that too quickly break down to a soup-like consistency. Conifer bark also contains suberin, a lipid sometimes referred to as nature's preservative. Suberin, more scarce as a presence in sapwood products and hardwood bark, dramatically slows the decomposition of conifer bark-based soils. It contains highly varied hydrocarbon chains and the microorganisms that turn peat to soup have great difficulty cleaving these chains - it retains its structure.

Note that there is no sand or compost in the soils I use. Sand, as most of you think of it, can improve drainage in some cases, but it reduces aeration by filling valuable macro-pores in soils. Unless sand particle size is fairly uniform and/or larger than about BB size, I leave it out of soils. Compost is too fine and unstable for me to consider using in soils in any significant volume as well. The small amount of micro-nutrients it supplies can easily be delivered by one or more of a number of chemical or organic sources that do not detract from drainage/aeration.

The basic soils I use ....

The 5:1:1 mix:

5 parts pine bark fines (partially composted fines are best)
1 part sphagnum peat (not reed or sedge peat please)
1-2 parts perlite
garden lime (or gypsum in some cases)
controlled release fertilizer (if preferred)

Big batch:
2-3 cu ft pine bark fines
5 gallons peat
5 gallons perlite
2 cups dolomitic (garden) lime (or gypsum in some cases)
2 cups CRF (if preferred)

Small batch:
3 gallons pine bark
1/2 gallon peat
1/2 gallon perlite
4 tbsp lime (or gypsum in some cases)
1/4 cup CRF (if preferred)

I have seen advice that some highly organic (practically speaking - almost all container soils are highly organic) container soils are productive for up to 5 years or more. I disagree and will explain why if there is interest. Even if you were to substitute fir bark for pine bark in this recipe (and this recipe will long outlast any peat based soil) you should only expect a maximum of two to three years life before a repot is in order. Usually perennials, including trees (they're perennials too) should be repotted more frequently to insure they can grow at as close to their genetic potential within the limits of other cultural factors as possible. If a soil is desired that will retain structure for long periods, we need to look more to inorganic components. Some examples are crushed granite, fine stone, VERY coarse sand (see above - usually no smaller than BB size in containers, please), Haydite, lava rock (pumice), Turface, calcined DE, and others.

For long term (especially woody) plantings and houseplants, I use a superb soil that is extremely durable and structurally sound. The basic mix is equal parts of pine bark, Turface, and crushed granite.

The gritty mix:

1 part uncomposted screened pine or fir bark (1/8-1/4")
1 part screened Turface
1 part crushed Gran-I-Grit (grower size) or #2 cherrystone
1 Tbsp gypsum per gallon of soil (eliminate if your fertilizer has Ca)
CRF (if desired)

I use 1/8 -1/4 tsp Epsom salts (MgSO4) per gallon of fertilizer solution when I fertilize if the fertilizer does not contain Mg (check your fertilizer - if it is soluble, it is probable it does not contain Ca or Mg. If I am using my currently favored fertilizer (I use it on everything), Dyna-Gro's Foliage-Pro in the 9-3-6 formulation, and I don't use gypsum or Epsom salts in the fertilizer solution.

As always - best luck. Good growing!! Let me know if you think there is anything I might be able to help you with.


New Port Richey, FL

Al,Thank You so much for the many,many hours that you have spent helping us to understand plants needs and how to provide them in simple, logical, easy to remember terms. Your knowledge is greatly apreciated and surpassed only by your unbelievable patience. Using your advice has greatly improved my results and actually cut down on the amount of time I spent trying to "fix" problems with my plants that were apparently due to soggy soil. Most of my questions have been asked by others and answered, but I still have a couple. Armed with better knowledge and more time I would like to try Bonsai again. Can you recommend a good forum, site, or book for beginners? And second, when mixing large batches of either mix and part of it being stored till needed should CRF and lime be added at mixing or added when the mix is actually used? Oh and 1 more. If CRF is added at planting do we still use a 312 fertilizer and how often? Again many, many thanks. susie

Bay City, MI(Zone 6a)

Having practiced bonsai for more than 20 years. and having seen hundreds of others fail because they can't keep their trees alive long enough to avoid the frustration that accompanies the death of the trees, I can say with a good deal of certainty that the road to success depends on gaining an understanding of how trees work (physiology) and how to keep their roots happy. Most bonsai books are heavy on the artistic aspects of the art, and too light on biology.

For understanding the artistic basics, the two books by John Naka - "Bonsai Techniques I and Bonsai Techniques II" are very good. Deb Koreshoff's book, "Bonsai" is also excellent. Also, the out of print Sunset book - "Bonsai" by Susan Lang (2003 edition) gives a surprisingly good overview of the subject.

For the science part, These are some books I've found to be extremely helpful:

All/any of Dr Alex Shigo's works

Plant Production in Containers II by Carl Whitcomb

Growth Control in Woody Plants and The Physiology of Woody Plants (2 different books) by Kozlowski and Pallardy

Growing Media for Ornamental Plants and Turf by Handreck and Black

Water, Media, and Nutrition for Greenhouse Crops (a Ball book)

Marschner's Mineral Nutrition of Higher Plants - edited by Petra Marschner

Plant Physiology by Mohr & Schopfer


It's ok to add lime & then store the soils, but don't add your CRF until ready to plant. I would try to find a CRF with as close to a 3:1:2 ratio (like 18-6-12) as possible, but make sure it includes the micronutrients.


New Port Richey, FL

Thank you

Virginia Beach, VA

i read the thread from 2010 you sound very knowledgeable and well informed. What is your major in College?

Very impressive!!


Grosse Pointe Shores, MI(Zone 6a)

Hi Al,

I just wanted to let you know that I used your 5:1:1 mix in every pot last year, and the results were outstanding! Especially my tomatoes. When we cleaned up the garden last fall, DH took the tomato stalks to the curb, roots and all...the container was nothing but roots! I was picking tomatoes until October!

Bay City, MI(Zone 6a)

Belle - my formal education ended when I graduated from HS. What I know about plants and related sciences is an outgrowth of my pursuit of a degree of proficiency at bonsai that would allow me to feel a sense of reward for my efforts (vs frustration - it's difficult to feel a sense of accomplishment when you can't keep your trees alive/healthy). When I first started chasing that goal, I had no idea I'd be doubly blessed by the opportunity to pass on some of what I've learned, and in doing that help others gain more from their growing experience.

Koshki - we're almost neighbors - probably shop at the same stores (like Bordines/Telly's) ...... I'm very glad the 5:1:1 served you well!


Virginia Beach, VA

What an accomplishment!!! wealth of knowledge!!! You must feel good about your knowledge and this can not be accomplished in short time. it takes a lot of reading and experimentation.Congratulations!!! I appreciate your patience on sharing your knowledge.


This message was edited Apr 17, 2013 3:52 AM

Provo, UT(Zone 5a)

im finding really good results with 5:1:1 mix..
right now all i have potted up with it are my amorphophallus..
i do water them a bit more..and i know when they go outside this
summer..i'll be watering them even more.. im good with that..
much thanks tapla!!! ive gleaned alot from your postings !!!!!
my only modification is i use pumice instead of perlite.. i use a 3/8 " size pumice
closest "larger" size to the pine bark fines ..
looking foward to this growing season..

New York, NY(Zone 7a)

Okay, I think I followed it this time. I've seen the soil in containers go bad. Does anyone know of a source of pine fines on Long Island? The Dee's, maybe, in Nassau County?

Much obliged!

Provo, UT(Zone 5a)

dawnsharon.. i dont live over there..but.. i would think lowes is out there???
i got 20 bags of there smallest pine bark mulch.. only $4.10 a bag..
good luck...

Virginia Beach, VA

Alabama has fine bark called soil conditioner. It is not available in Virginia.


New York, NY(Zone 7a)

I used the smallest pine bark mulch I could find; seems to be semi-composted. I bashed holes in the bottom of the container and stuck landscape fabric wicks through them. I'm not ready for the 5-1-1 mix yet (for one thing, I didn't sieve the mulch, so there are probably too many long shreds of bark in it) so I compromised on a 1:1 mix of mulch to Fafard container gardening mix. I guess I'll find out how well it works this season...

Springfield, OR(Zone 8a)

Wow, I made it in time! I've been reading for days and think I've now read every word you've posted since 2007 on this and related threads, eventually beginning to wonder "oh will it still be going in 2013?" And Viola, as we say 'round here. Lucky me.

So I feel pretty sure I've got the concept. You are very articulate not to mention generous. I do still have two questions, the first of which you did actually post at one point but I couldn't find it when I wanted it. It's this: was it the Whitcomb book you referred to as the bible of container gardening?

And when rooting cuttings of schefflera you mentioned using rinsed perlite in a gallon milk jug with the capped top part retained for conserving humidity. My question is do you pierce drainage holes in the bottom of the jug? It seems an odd question with all this learning about water retention, soggy soils, and such. But maybe we're not talking about soil here at all but a rooting medium?

Ah, and of course; comes a third question to mind. When using a wick for root first aid until actual repotting into a useful soil can take place, does it, the wick, not have to go up to the PWT to be useful? Is just being somewhere in the perched water, like the bottom, enough?

I can only add all my thanks to those of everybody else blessed by your hard-wrought knowledge and generosity. I'm glad I thought to wonder about pruning my scheff. I'd say wondering can lead us to some wonder-full places!


Bay City, MI(Zone 6a)

Thanks so much for the kind words, Turtle! ;-)

In Plant Production in Containers II, the production strategies Dr Whitcomb discusses are written so they are easy to understand and borrow/apply to our hobby growing endeavors. If you plan on working toward becoming a proficient container gardener, you'll gain a lot from the book.

See the little milk jug greenhouse below. The top part has some vertical slits in it so it will slip into the bottom part - and the bottom part has 4 drain holes (because the bottom has ridges for support that sort of form 4 individual reservoirs that need 4 drain holes to drain properly. I root a LOT of cuttings in just the gritty mix. It works great.

Wicks work best when they're in contact with the bottom of the pot, with the tag end dangling 1-several inches below the bottom of the pot until water has stopped dripping off the wick.

Best luck ...... and have a good weekend!


Thumbnail by tapla Thumbnail by tapla
Springfield, OR(Zone 8a)

Got it. Thank you. I have most of the gritty ingredients; just have to find someone who drinks milk :~)

I hope you are especially appreciated on Monday.


Chevy Chase, MD(Zone 7a)

Tapla: Thanks for the recommendation of Plant Production in Containers II. Amazon gives it a 1984 publication date -- and a used version is in the hundreds of dollars. Then there is a revised version, without the "II" and with a later (1988) publication date. A used version of it is available for much much less.

Do you happen to know whether the "revised" version without the "II" supersedes the "II" version?

Bay City, MI(Zone 6a)

The edition I have was copyrighted in 2003, and I think that's the latest edition. In the information, it says the 2003 edition is dramatically expanded. The 2006 edition is essentially the same book with a cover make over & new format. It says you can buy it straight from Lacebark for less than $75 delivered to your door:

ISBN 0-9613109-6-0


Chevy Chase, MD(Zone 7a)

Thanks, Al.

Springfield, OR(Zone 8a)

Well, I might be doing something right: yesterday my VSO popped out to watch me mixing container medium and said "that's reminiscent of the stuff my mother grew orchids in."
Actually I haven't gotten it quite right yet, but I think I'm on the right Interstate!

Bay City, MI(Zone 6a)

Growing in a soil you don't have to fight, one that works FOR you instead of against you, will significantly increase YOUR potential to offer your plants the best chance at reaching their potential. Watering and fertilizing suddenly becomes MUCH easier, and being able to avoid over-watering will be something you're soon taking for granted.


Springfield, OR(Zone 8a)

Thank you Al. You're a treasure.


Provo, UT(Zone 5a)

add my thanks to al for his discussions here on potting mix..
im using a "sort of" 5:1:1 mix..
with my tropical potted plants..mostly amorphophallus(potted )
i use 60-70% shredded pine bark, 10-15% large sized pumice
and rest of peat..sometimes i substitute the peat for compost..
im very pleased with the drainage the pots are getting ..
i do water more..but im good with that..
i just put the pots..alot..nearly 200 now..all sizes.. over the lawn when i water..
let the lawn benifit from watering/fertilizing..then move pots back to there sitting
there is some water retention.but not like with a high peat/coir based potting mix..
much thanks for the excellent discussion here !!!!!

Bay City, MI(Zone 6a)

Thanks for the very kind words, guys. It's surprising how much easier growing is if you don't have to fight the soil you're using, and how much more realized potential you can expect when you don't have to work within the confinements of an inherently limiting medium. The recipes are a good starting point, but it's really the understanding of how water behaves in soils that paves the way for the ability to get soo much more out of growing.


Thumbnail by tapla
Provo, UT(Zone 5a)

ive gardened for ever..LOL..and always gave thought to drainage..whether plants
were in pots,planted out in garden..
and i think i had moderate success ..i am lucky where my property is..its old river bottom
a TON of rocks only inches below the surface..
but with pots i know i saw mediocre success with various plants.. always thought..i gotta
get a handle on this..
al..your postings and the feedback from others looking at "how does the water flow" in that pot..
like a light come on !!!
ive mentioned before with my huge pots..i find even more need for good water flow.. biggest ones
hold almost 5 cf of potting mix..geeesshhh.. LOL
my amorphophallus have always done ok..but tropical ones..needing potting mix to always stay
"moist" ive struggled with..
im not this yr.. YEA.. even the biggest pots.. good drainage, ya..i water more..but no problem of
stagnant water in the pot..leading to rot,disease...
much thanks for insights..experiments,observations from you all !!!!!!!!!!!!!!!!!!!!
rock on al !!!!!!!! :)

Everett, WA(Zone 8a)

Thanks again, Al. I repeat your message every time someone wonders why their seedlings or plants died from root rot.

There's one part of your message that I want to repeat, because it took me the longest to learn.

If you have a mix partly mixed up, and it's very coarse and gritty compared to what most of us have used for years, or bought in a bag ...

and you are tempted to increase water retention, (as I am), by adding "some" traditional peat-based potting soil such as Fafard or ProMix or Sunshine ...


Or at least, never add more than 12% to 14% (1/8th to 1/7th).

Remember that the POINT of the gritty mix is to create open voids and channels for water and gas to flow through. Your gritty mix might only HAVE 10% to 20% open space. You probably already have some bark powder and fine bark fibers. How much "fine stuff" you already have depends on how you screen your bark and how much composting broke it down.

If you add 15% peat moss, or sand, or anything very much smaller than 1/10th inch (2.5 mm), you are FILLING the voids that you just went to great effort to create.

So aim to add less than 10% peaty stuff, if any. I now lean towards easing up on carefully I screen out all the bark fines, instead of deliberately adding any peat.

I keep making a big, nice batch of excellent texture, then ruining it by adding twice as much peat as I should have.

Then I have to re-make the whole batch, doubling its size to dilute the evil peat fines , and discipline myself to add NO peaty stuff.

I wish I could think of something that would bind up peat fibers and powdered peat, and bark dust, into some kind of sturdy, porous pellet like a clay ball or 2 mm x 2mm peat-ped. Then it could retain some water without filling all the pores in several cubic inches of gritty-mix.

Thumbnail by RickCorey_WA
London, United Kingdom

After hours scouring the web for good advice on soil, this forum seem to offer certainly the most intelligent advice for those of us such as myself without a lot of experience with houseplants! Unfortunately in the UK we don't have some of the recommended soil ingredients such as Turface... To try to apply your same principles for my own circumstances, I've come up with the following proposal:

- 60% Hydrocorn (Baked clay pebbles 8-16mm in diameter, and I'm trying to source the 4-8mm diameter pebbles instead).

- 30% 5mm coco husk chips, fine grade SSS recommended for growing orchids.

- 8% organic worm humus castings

- 2% Plagron Bio Supermix (slightly redundant, but a mix of various supplemental fertilizers).

I wasn't sure about adding gypsum though, as that seems to be advertised as breaking down clay, and I didn't want it doing that to my clay pebbled?

Other possibilities, such as crushed granite, lava grit, and pumice are the wrong size or very expensive in comparison.

I'd be using this soil to grow houseplants such as Kentia Palms, which don't like to be repotted, so I'd like a soil which keeps structure/drainage/aeration permanently. I'd also be using this primarily in self-watering pots, which suggest alternating top-watering and reservoir refilling about every two weeks.

My thoughts are that these soil ingredients might retain some dampness and nutrients to help keep these available, and thus not being as dry or sterile as say a gravel/bark dust mixture would. I was worried about the fertilizers being depleted if the only nutrients were in the water which is added to the reservoir at the bottom which the plants will send roots into.

Might this work decently well, or would you have any alternative suggestions please? (Let me know if this is off-topic and should be in a new thread by the way)

This message was edited May 17, 2015 4:01 PM

London, United Kingdom

Not to mention that hopefully I can revive and keep this thread live still!

I also have 8 Mexican Fan Palms I need to plant outside, which like dry roots during winter which is not the norm here in London. I'm thinking of digging up a 3 foot diameter hole where I'm planting each one, and mixing that soil with something like: perlite, bark chips, 4mm course stone grit, and worm castings to create a free-draining soil in which they might grow well. And I'd try to mound that up by maybe a foot to keep the palm's 'feet' dry during winter. Might this be okay as well?

Everett, WA(Zone 8a)

- 60% Hydrocorn (Baked clay pebbles 8-16mm in diameter, and I'm trying to source the 4-8mm diameter pebbles instead).

- 30% 5mm coco husk chips, fine grade SSS recommended for growing orchids.

Thumbnail by RickCorey_WA Thumbnail by RickCorey_WA
London, United Kingdom

Anyone have any advice on my questions 2-3 posts up please??

Bay City, MI(Zone 6a)

You might have access to a calcined clay product called Seramis. It's a good product.

The concept embodied in this thread is more important than the recipes; so, if you understand the concept you'll also understand there are many ways to implement it.

In a perfect world, the mineral fraction for use in the gritty mix would range in size from about 1/10 - 5/32" (.100 - .156" or from about 2.5 - 4.0 mm) The bark fraction would be slightly larger to allow for some breakdown over the life of the planting ........ from 1/8-1/4 is about ideal (.125 - .250" or about 3.25 - 6.25 mm) .

I'd tend to stay away from CHCs as a significant fraction of a medium (more than 10%) because of several issues that need to be taken into account if you're to expect best results. Try to find pine or fir bark and use that if possible.

Skip the ingredients aimed at feeding the plant at the expense of aeration. They don't provide anything you can't get from a bottle (of synthetic soluble fertilizer). If you do your research, you might find a fertilizer in a 3:1:2 ratio (RATIO is different than NPK %s) that contains ALL the essential elements in one mixture. I use Foliage-Pro 9-3-6, which has everything, including Ca and Mg, elements more often than not lacking in soluble synthetic products. Concentrate on the medium's ability to provide a favorable combination of air and water, and take responsibility for the plant's nutritional needs on your own shoulders. That part is monkey easy, so there is little reason to sacrifice soil structure on the altar of nutrition.


This message was edited May 24, 2015 9:33 AM

Somewhere in, MD(Zone 7b)

I always learn something crucial when reading your posts Al, thank you. :)

London, United Kingdom

Many thanks Al, and that's very helpful.

I was hoping I had the principles correct, but wasn't sure so I thought I'd better ask those more experienced before making a long-lasting mistake!

I'll order the smallest pebbles I can in that case, which are the 4-8mm ones, and mix that equally with small bark.

What is the issue though with Coconut Husk Chips? I was a little concerned about fir bark, as I thought it might have allopathic properties, but I researched it and it seems to be the needles rather than the bark which has that, and that seems to affect primarily germination rather than growth in any case.

In a hydroponic reservoir system such as with such 'self-watering pots', is anyone aware if there is a danger of the plants immediately soaking up all the nutrients when refilled thus overdosing, and then not having sufficient nutrients for the following few weeks?

Thanks for the recommendation on fertiliser as well, which was to be my next line of research and that one is available here and seems to have rave reviews from the THC community...

I had found Seramis available, but was put off by its bright crimson colour which had much the appearance of red cat food and was a bit pricey... So the darker brown colour of the clay pebbles topped with bark is I think preferable.

Bay City, MI(Zone 6a)

Hobby growers talk among themselves about what is or isn't the right fertilizer, but I've not once seen an indication that a grower actually sets about fertilizing with an idea of when he/she is trying to achieve; so, I decided to look at things from the plant's perspective, then relate what they would want. So far, no one has improved on the description of what I think we're trying to achieve.

The goal for fertilizing containerized plants can easily be described. Ideally, we would work toward ensuring that all the nutrients plants normally secure from the soil are in the soil solution at all times, in the ratio at which the plant actually uses the nutrients, and at a concentration high enough to ensure no deficiencies yet low enough to ensure the plant isn't impeded in its ability to take up water and the nutrients dissolved in water. This goal is easily achievable using one water soluble synthetic fertilizer. You CAN use organic forms of nutrition, like fish/seaweed emulsions or various types of meal, but that makes it much more difficult to achieve the goal. That about sums it up. Our job is to find the easiest and most foolproof way th achieve those ends.

The problems with CHCs:

* They have a high pH (around 7) which precludes the use of dolomite as a liming agent
* They have a very high K content, that should be taken into account when formulating a nutritional supplementation plan
* They are often very high in salinity due to being ponded/processed in salt water
* Several studies have also shown that the significant presence of phenolic allelochemicals in fresh coir can be very problematic for a high % of plants, causing poor growth and reduced yields.

When it comes to nutrients, plants will tend to take what they need and leave the rest. When there is a high level of one or more nutrients, it's not so much that the planty is in jeopardy of 'over-dosing'; rather, it's usually an antagonistic deficiency (too much of one nutrient making it difficult for a plant to assimilate enough of another - common antagonisms are CA:Mg, Fe:Mn. and P:Fe [VERY common when using high-P fertilizers]) or a high TDS/EC level in the soil solution that makes it difficult or impossible for water to move into cells.


San Diego, CA(Zone 10a)

Unable to locate the correct size of crushed granite for the gritty mix. All I've found locally is 3/8" as shown on the left. Way to large, right?

They DO have have another product much closer in size, shown on the right. It's considered a 'decorative' product. Can I sub this in place of granite? (not sure what specific rock it is.....doesn't appear to be porous.

Price per .5 cu. ft. bag
3/8" crushed granite $6
'decorative' product on right $19 (OUCH!)

No Gran-I-Grit could be located, and poultry growers grit found is way too pricey ($13.99 / 7 lb. bag)

Thumbnail by mickkkkyd
Bay City, MI(Zone 6a)

Too large. Make a last try for the grit before using the smaller product above? At feed stores that cater to those who raise poultry, you should be able to find #2 cherrystone or MannaPro Poultry Grit. Some chain farm supply stores also carry the MannaPro in 50 lb bags for less than $10.


San Diego, CA(Zone 10a)

Thanks for your direction Al. Yesterday when I made MANY phone calls for local feed / farm supply stores within a reasonable distance, I tried searching the internet until my eyes bled, and I also thought outside of the box for other alternative sources of correct sized / reasonably priced media, with the criteria that it had to be inert / non water soluble / non-porous.

I saw where in the midwest, the #2 cherrystone grit can be purchased for ~$6 per 50 lb. bag. ($0.12 / lb.). None available in the San Diego area however.

Your other suggestion MannaPro was found at several local stores but only in 5 lbs. bags which consistently ran $9.99 ($2.00 / lb.). Since the stores are 'authorized distributors', I asked for them to see if they can get larger bags special ordered.

I am going to try contacting the San Diego Bonsai Club to see if they might have a source of product. Will keep the thread updated in the event another reader in my region may be interested.


Everett, WA(Zone 8a)

Maybe places that sell concrete products would have a well-screened crushed stone product that isn't too pricy.

If the problem is too-much-dust, you might be able to blow that away with a big fan (winnowing).

You can screen out grains that are much too big, using 1/8" hardware cloth.

But it might be hard to screen out everything you don't want, like smaller than 1/10" but too large to be blown away.

I also found that "co-ops" will sell a few pounds of something in a small, fancy bag at the same price as a big, 50-pound plain bag. But you have to ask for the big bag or pay ten times as much.

I had to ask "whadda ya got in the warehouse?"

San Diego, CA(Zone 10a)

I think I've FINALLY found a descent product for Al's gritty mix. Got the clue from the San Diego Bonsai Society. Located it at a roofing supply store. It's 'A-1 Products Granite Roofing Granules / Poultry Grit #5' from SG Wholesale Roofing Supply Inc., Lemon Grove, CA. (hop, skip, and a jump from San Diego) 80 lb bag (7/8 cu. ft.) for $7. I liked the $0.09 per pound price!

Not sure if I should further screen to size????

Thumbnail by mickkkkyd Thumbnail by mickkkkyd
Everett, WA(Zone 8a)

>> Poultry Grit #5

Cool! I only found #2, and it seemed slightly smaller than I might want in a 5 gallon bucket. No one ever told me they had "turkey grit".

I'll expand my search to include "roofing supplies". You might also search for "aggregate".

I like the way those grains are irregular in shape ("sharp" grains).

It does look like many of your grains are bigger than 1/4" and some bigger than 3/8".

I would think that trying to remove some of the bigger grains would be desirable, especially for smaller containers where the actual volume of the root zone is not large. Large grains of granite do take up volume.

In this case, I bet that 1/4" hardware cloth would hold back SOME of the too-big grains. Several quick passes over a slanted 1/4" sieve would pull out the biggest ones without holding back anything desirable.

1/8" hardware cloth would hold back ALL of the big grains, and maybe some desirable ones. After using 1/4" mesh, force as much of the smaller stuff as you can through 1/8" mesh, rubbing them back and forth with the back of a rake.

Then decide whether you've removed too many medium-sized grains.

If too many large grains are screened out to just throw away or use as drainage gravel, I wonder of you can break some of them up with a big hammer and some hard surface. Or by heating them really hot under a broiler and then throwing them into cold water (from a safe distance).

But I would defer to Al's opinion in a heartbeat.

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