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Container Soils - Water Movement & Retention XIII

March 17, 2011

I first posted this thread back in March of '05. Twelve times it has reached the maximum number of posts GW allows to a single thread, which is much more attention than I ever imagined it would garner. I have reposted it, in no small part because it has been great fun, and a wonderful catalyst in the forging of new friendships and in increasing my list of acquaintances with similar growing interests. The forum and email exchanges that stem so often from the subject are, in themselves, enough to make me hope the subject continues to pique interest, and the exchanges provide helpful information. Most of the motivation for posting this thread another time comes from the reinforcement of hundreds of participants over the years that the idea some of the information provided in good-spirited collective exchange has made a significant difference in the quality of their growing experience.

I'll provide links to some of the more recent of the previous dozen threads and nearly 1,800 posts at the end of what I have written - just in case you have interest in reviewing them. Thank you for taking the time to examine this topic - I hope that any/all who read it take at least something interesting and helpful from it. I know it's long; my hope is that you find it worth the read.

Container Soils - Water Movement and Retention

A Discussion About Soilssize>color>

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.

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 Water Movement information.

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 improve it's aeration or drainage characteristics by adding larger particulates. Sand, perlite, Turface, calcined DE ...... none of them will work. 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 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.

My Basic Soils ....

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.

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

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.

If there is interest, you'll find some of the more recent continuations of the thread at the links below:

Post XII

Post XI

Post X

Post IX


Post VII

If you feel you were benefited by having read this offering, you might also find this thread about Fertilizing Containerized Plants helpful, as well.

If you do find yourself using soils you feel are too water-retentive, You'll find some Help Dealing with Water-retentive Soils by following this embedded link.

If you happen to be at all curious about How Plant Gowth is Limited, just click the embedded link.

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


Comments (152)

  • PRO

    I generally wait until I see some initial new growth emerging before I fertilize. While I understand that a full compliment of nutrients in the soil is required for normal growth, there is enough evidence out there that suggests that withholding fertilizer for a short period after repotting helps the plant colonize the entire root mass more rapidly. Is it a make or break kind of deal? NO, not at all - just another way to gain a little edge by getting the entire soil mass colonized w/roots asap. Since the gritty mix should hold almost no perched water, allowing roots to easily colonize the entire soil mass, the practice would probably be most beneficial in the 5:1:1 mix or in heavier soils, but I still wait a week or two before starting regular applications of fertilizer, even when using the gritty mix.


  • jojosplants

    Hi Al~
    Thanks! :-)
    I did withhold the fertilizer on the few containers I have already done. The plants are growing good now! In both the 5-1-1 and the gritty. So I went ahead and fed them today.

    It was just something I was curious about, not seeing the smaller plants talked about much.

    I will try and post a few pictures a little later.

  • organic_wonderful

    But tapla, am I right in saying that if watering them just before I leave won't be enough, using capillary matting will with a small reservoir will keep them alive whilst I'm away?

    Also, more importantly, can I use the 5-1-1 mix with the amount of dolomite lime you recommend in the first post in this thread to grow strawberries? Or should I use less dolomite?

  • greentiger87

    Thanks Ohiofem and Al for the the clarification, I think I've got my head wrapped around it now. I wish I could edit that post so that it doesn't confuse other people though :(

    I've been making a lot of the gritty mix lately, as I have a lot of houseplants. I've held off on buying new plants this year until I got all the ingredients for it, so I have a lot of shopping to make up for. So far, my transplants are really loving the mix! Little or no transplant shock, which is remarkable considering the leaf drop I usually see. I'm using decomposed granite with the largest pieces screened out and the smallest particles sifted out with insect screening and washed away with water. This makes it a little more water retentive than the proper mix would be - but it's working great for my purposes.

    A couple of things that I think might add some more clarity to the original post:

    1) explicitly title the "5:1:1 Mix" and the "Gritty Mix" as such and spell out the part ratios with a brief description of their function

    Something like:

    5:1:1 Mix
    For short term plantings of 1- 2 years, cheap and relatively easy to find ingredients

    5 parts pine fines
    1 part perlite
    1 part peat moss
    1 tbs dolomitic lime per gallon of mixture

    Pine Fines - physical support for roots, relatively large particle size increases aeration and decreases the PWT, still retains some water and makes nutrients available to plants, cheap and light material that makes up the bulk of the soil mixture

    Perlite - prevents compaction upon decomposition of peat and bark, increases drainage, retains some air and water internally, large particle size increases aeration and decreases PWT

    Peat Moss - retains both moisture and nutrients extremely well, drains well when "fresh", but decomposes fairly quickly

    Dolomitic Lime - raises and buffers the acidic pH of pine bark and peat moss to a level appropriate for most plants, provides Mg and Ca that are often absent from average fertilizers


    My "functions" are just guesses, but you get the idea

    The "batch" information is just confusing, IMHO. When the ratio is clearly stated, the need for the specific recipes is obviated.

    2) Be more clear about particle sizes for each material. What "pine fines" are, in terms of what the ideal material. For example, I know in another thread, Al stated that "pine fines" should be anything from dust to 3/8 inch, but I still got turned around because it wasn't in the original post.

    Something like: (perhaps combined with the above)
    Pine Fines - Ideally, this should be composted pine bark with a particle size from dust to 3/8 inch, with a fairly even distribution. Larger particle sizes will provide even better drainage, but require more frequent watering. Smaller particle sizes will increase water retention, but also promote compaction and a higher PWT. Very large pieces of bark should be screened out, ideally using a 3/8 inch screen, or a 1/2 inch screen if the former is not available.

    Perlite: Coarse perlite is best, but some dust is generally unavoidable. Screening out this dust is unnecessary, but you could do so to even further promote drainage.

    Peat Moss: Particle size is irrelevant, no screening is necessary.

    Again, just guessing from my understanding.

    3) Put the just the titles of the soil mixtures and the ratios of ingredients at the top of the post, before the discussion. This both lets people know where things are going, and helps when people come back and just need that information.

    Just my humble suggestions... I know the post has lasted a long time and informed a lot of people, so I totally understand if you'd rather leave it alone.

  • PRO

    OW - I can't answer your question w/o some indication of what kind of conditions they'll be left in, and some sort of feel for how much water retention you've built into the soil. I CAN say that if you want to extend the length of time your soil will support growth, putting the plants in a cool/dark garage or shed, out of any wind, will go a long way toward stretching out the length of time the soil will hold an adequate volume of water.

    Thanks for the suggestions, GT. I'll try to remember to revisit your post as I consider any revisions .... if I'm lucky enough for it to go to 14 reposts w/o fizzling. ;-)


  • greentiger87

    Lol, Al - your struggle to be modest in the face of well-deserved praise is quite endearing. With more and more people getting into urban gardening, I highly doubt this post will be fizzling any time soon...

    organic_wonderful, how big are your pots? There are too many variables for anyone to give you a concrete answer... you'll just have to try it and see. I've used ollas in the past to great success for irrigation while I'm away - google it, quite an interesting and simple concept that works spendidly. Try Hobby Lobby for cheap terra cotta wine coolers that are very close to an ideal shape - long/deep, relatively narrow, and no drainage holes. Fill with water and bury in the ground, cover with something heavy enough to prevent evaporation.

  • filix

    Five yards of uncomposted pine bark. Now all I need is someone to help me sift this! This thread has been a god sent for me. Im going to grow some tomatos in containers this year for the first time, as I left my raised beds at the old house. Do I skip the lime and add just gypsum to the 5.1.1? Many thanks A1!


  • greenman28 NorCal 7b/8a

    Hey, Filix, nice pile ;-)
    Add the Lime - not the gypsum.


  • PRO

    Agree .....


  • filix

    You would think I would know that by now. After making this stuff for six years now. :) Thankyou. I will think of you both when I eat my salad! filix.

  • jenn

    I have been hanging out at GardenWeb for many years and just now caught these discussions about Al's gritty mix for container gardening. I do mostly in-ground planting but have a dozen or so outdoor plants and always used commercial potting mix with some perlite. I'm always seeking the "best" method to keep our plants happy and thriving for as long as possible.

    I just found a very local resource for the Turface (yay!) and called to verify they have some in stock.

    Anyhoo......... I'm wondering about the statements made by some who use the gritty mix (1:1:1) and say they use it for "all" their container plants with great results. Does this mean all those plants have the same type of soil requirement, or is the gritty mix simply the base into which a variety of nutrients (seaweed emulsion, CRF, iron, etc.) are added and other variables (pot size/type, watering) changed based on the needs of each plant?

    Say I want to grow southwest Agastache, Lavender, and Penstemon in the gritty mix. Since we have a very long growing season, they will live over into the following year and I'd like to not have to plant them again each year. The Agastache and Lavender like lean fast-draining soil, but the Salvia (not all of them, but this one) likes a richer (but well-draining) soil. Would I use the 1:1:1 mix for all of them, but add more nutrients for the Salvia? Or, would I use, say a 3:1:1 mix for the Salvia?

    For tomatoes (short-term seasonal plant) wouldn't I use the 5:1:1 mix?

    And what about succulents? I don't understand how succulents and, say, geraniums would be equally as happy in the same mix --- unless other factors are involved including pot type (clay vs. plastic), mulch type, additional nutrients, frequency of watering, etc.

    Can someone explain this, or point me to an existing link that explains it for me?

    Thank you...

  • PRO

    It's important to understand that many of the recommendations offered for particular plant's root wants/needs aren't based on the assumption that you'll be using a peaty, water-retentive soil. You can toss out the idea 'likes to be root bound' if you use a fast soil because 'likes to be root bound' is code-speak for 'doesn't tolerate wet feet. A plant in a small volume of soil uses the water in that volume of soil faster, so air returns to the soil faster and roots don't rot. The problem is, tight roots are an impediment to growth and reduce vitality; so why not use a really big pot, put the plant in the gritty mix, and let the plant grow to it's full potential (within the limits effects of other cultural factors)?

    What does 'a richer' soil mean? Blacker? - like 'good' garden soil? ...... another commonly held belief that needs debunking. If you were willing to do the watering it required, you could grow healthier/larger plants in a bucket of broken glass than you can in a heavy peat soil like Miracle-Gro. It's true. I'll explain why if anyone doubts.

    The thing is, Jenn, almost all plants do best in a damp, highly aerated medium that contains enough nutrients to prevent deficiencies, but not enough that toxicity becomes an issue or that an excess inhibits water uptake. The growers that have the greatest success don't depend on the soil to supply nutrition for their plants. They shoulder the burden of ensuring their plants have all the essential elements available at all times. The must efficient and productive way of doing this is with regular doses of soluble fertilizers.

    I don't choose a soil based on what I think the plant will prefer - they pretty much all prefer the gritty mix over anything else I've ever used - I choose the soil based on how long I thing that planting will remain in that soil. All my mixed display containers & veggies go in the 5:1:1 because I turn it into the compost pile at the end of the year. That's my preference - it can be pressed into longer service & even amended so it remains useful into the 3rd & subsequent years if required. Everything I know will be in the same soil for 2 years or longer goes in the gritty mix.

    Keep in mind that just because you use a long lasting gritty mix, it doesn't release you from having to keep up with your repotting & root work to keep plants happy. If you hang around for a while, you'll come away with a broader perspective of managing your container plantings, one that looks at container culture in a more holistic manner.

    More questions?


  • arkf

    So I looked a bit but didn't see an answer to this question. With pine bark for the gritty mix, is there an acceptable amount of wood that can be mixed in with the bark?

    I can't seem to find any bark without at least some wood in it. I found some Permagreen brand bark mulch, which looked like good sized particles but it had maybe 10-15% wood, roughly speaking. Even the Repti-bark at the pet store had wood chips mixed in, again maybe 10%.

    Will that work, or should I keep looking? Or try to pick out the wood by hand, which doesn't sound fun.


  • jenn

    Al, thank you SO MUCH for your very informative reply. Boy oh boy, the things I have learned today -- including how much I did not know!

    So then, whether a plant tag calls for "porous" or "peat-based" or "rich" medium (using the industry terms), all would do equally well in the same gritty mix as long as soluble fertilizer is applied according to the needs of each plant -- correct?

  • PRO

    Noah - I think that most bark products have at least 5% sapwood in them, and I'm sure some have more, You're probably fine as long as it doesn't get excessive - like you might have to call it wood chips instead of pine bark. The less sapwood you have the better, but if you find something that has a good particle size distribution - use it.

    Jen - I'm laughing because I just came from a thread where kind Mr Sam said exactly the same thing - now you're being kind, too. What a good day it is when we're all kind to each other, eh?

    Yes - you have it. I don't know if I said it when I replied to you, but you'll do much, much better as a container gardener if you set your focus on 'structure' and soil longevity and forget about depending on the soil for any nutrition. 'Rich' and 'black' are nice and desirable in the garden, but they mean nothing as adjectives for container media, and in fact can be detrimental if they are accompanied by excessive water retention, and they very often are. I hope you come away wanting a soil that will remain well aerated for the intended life of the planting. That is always my focus when I establish a planting, and IMO is the issue that your effort:reward quotient is most likely to pivot on.

    Thank you for the kind words.


  • jenn

    What a good day it is when we're all kind to each other, eh?

    Yes, it sure is. :)

    I hope you come away wanting a soil that will remain well aerated for the intended life of the planting.

    I already do! I'm excited to read more and get started, first with the Nagami Kumquat (see new post in Citrus forum) that needs re-potting.

    I'm having some health issues that I hope to be resolved soon, and may not be able to start re-potting other plants until next month, maybe early summer. I hope it won't be too late.

  • jenn

    And thanks for graciously answering a question that's probably already been answered a billion times somewhere in this forum. :)

  • PRO

    I don't mind the repeat questions, Jenn. It keeps the information in front of people, and I realize it's difficult to sift through reams of random conversation to find answers to all your questions ..... and your ample enthusiasm is cause enough in itself to make people want to help you. Almost everyone comes here willing to put forth a good part of the effort to do the lion's share of what it takes to understand container gardening. The very few that occasionally pop up, wanting it all spoon fed to them stand out (none of that lately, though), and bring to mind what my mom would tell me when I would ask her to do something for me I had the time and ability to do myself. She would say, "God helps those that help themselves". I'm sure I didn't like it much way back when, but I'm also sure it helped me become a more self-reliant adult.

    This is all fun for me. I enjoy sharing what I know, and look at my time here as a natural extension of my quest to learn how to grow things better. That the things I've learned along the way have proven helpful to you & others is a win/win deal, the way I look at it. ;o)

    Again, your kind words are appreciated.


  • jenn

    Al, I really appreciate your taking the time and allowing repeat questions -- you're right, it would be difficult to sift through all the information already posted. I have bookmarked several pages about soil and container gardening to read on the side. I'm inclined to be very inquisitive, my favorite question usually being "why?" -- i.e. why is the gritty mix better, or why is liquid seaweed a good fertilizer -- so I can make informed choices and explain why to others who might ask.

  • PRO

    Lol - I've always been very careful about not operating at beyond the limits of my knowledge. IOW, I know what I DON'T know. If there is a topic being discussed and I don't think I have all my ducks in a row, I just don't say anything. When I DO enter a discussion, it's either because I think I can contribute something helpful, or because I think someone has offered advice that might be harmful to someone's growing experience & it needs to be examined a little more carefully. In many cases, this later proclivity has hurriedly 'unendeared' me to a few, but that brings us full circle to the thought that just repeating something you heard, read, or have been doing for 100 years may not be the best advice, or even good advice, when examined in the light of other options.

    Getting back to your comment about "why", I think that it doesn't hurt my credibility at all that I'm usually always able to answer the "whys" resultant of follow-up questions to my posts. If I didn't know 'why', the fact that I make it a point to abstain from posting at beyond the limits of my knowledge would have prevented me from posting anything in the first place.

    Curiosity and enthusiasm, with a liberal measure of ambition, is the stuff that not only propels budding gardeners, but makes them fun to interact with. Your questions are welcome. If I don't know the answers with certainty, I'll say so before I make anything up, but more likely I'd go looking in a trusted source for the answer - because NOT knowing would bug me. ;o)


  • hayden2

    I'm so confused. How do you guys get the ingredients? I have 2 citrus trees, 10 years old, grown from seed. I'm concerned about their long term life span. I live in the northeast, so I have to move them constantly between inside to outside during the spring and fall. So I can't do pots more than say 16 inches.

    I've tried the largest - and they're big - gardening stores around here, as well as the local home depots and lowes'. When I ask for pine bark fines, or turface, I not only get blank looks, they tell me no one has ever heard of such a thing, and I must have misunderstood. I tried once asking for orchid mix, and they showed me bark that was about 4 inches by 2 inches in size. Try putting that through a screen!

    It seems the best I can do right now, after speaking to the manager of the largest gardening store in our area (4 - 5 acres of plants) would be a plastic bag of cactis/palm/citrus soil, with added perlite or something. Anything else would cost about $500 (i.e, the cost of a plane ticket to California), according to this guy.

    I live in the northeast, where citrus growing in containers is not really common.

    Any ideas? Thanks.

  • jenn

    Words to live by, Al! I often jump to give an answer, and then don't because I'm not 100% certain it's 100% correct, or complete (and I'm sure I'm not 100% correct about that either, LOL) and I don't want to mislead anyone. But if I know the answer then I love to share it, to help and give back some of what I've learned at GW and in my own experience over the years.

    I've done primarily in-ground gardening for the past 15+ years, but have added pots here and there for decoration, or when there isn't room in the garden for a particular plant that I just have to have or it won't tolerate our heavy rich clay soil -- everything form a dwarf Kumquat, to succulents, perennials and herbs, and a handful of houseplants. I'll slowly convert them in some order of priority to one of these mixes. I may even experiment with a pair of identical plants -- 1 grown in gritty, and 1 grown in good bagged commercial mix w/ a handful of perlite mixed in -- just for the sake of comparison.

    If nothing else, I've seen the photos of the gritty mix and it is gorgeous! Like a beautiful multi-color mulch.

  • PRO

    Hayden - sometimes you just have to lay down some tracks to find the bark. What you want will look like what you see at 12,3,6 or 9. At 12 is a prescreened fir bark in 1/8-1/4" that is perfect for the gritty. The other 3 pictured are from different suppliers, but show bark that could be used 'as is' for the 5:1:1 mix or be screened for use in the gritty mix. @ the middle you'll see what the 5:1:1 mix looks like when dry.


    If we knew where you lived, we might be able to help you find the Turface MVP or Allsport (same product). For the grit, you'll probably have to call around to feed stores or elevators that cater to rural populations that would be raising fowl livestock. Ask for Gran-I-Grit in grower size or #2 cherrystone. If you get a "huh?", tell them you're looking for crushed granite chicken grit, and ask if they have suggestions as to who might have it if they don't.

    Jenn - If you decide to experiment, please keep us posted. I started out by trying to 'improve' bagged mixes by first adding more perlite to try to get them to drain better. I found it didn't work well. Then I discovered pine bark because I was getting trees from the nurseries in bark mixes. I soon discovered that it took a really large bark fraction for the bark to make a difference - at least 75% is about the tipping point. About the time I figured that out (almost 20 years ago, I was gaining an understanding of the physical properties that determined water behavior in soils. From there, I started researching various ingredients & discovered some of the ingredients bonsai practitioners were using in their soils (dozens of ingredients). I settled eventually on the Turface & granite, along with the pine bark as the best choices of ingredients to perform a particular job in the soil. Even though I've been listening to others talk about soil ingredients and tinkering with soils myself, it's been more than 15 years since I started using the gritty mix & haven't yet found anything that even held the promise of being a healthier root medium.

    It IS important to understand that the recipes I offer are only the best ways I have found to implement the CONCEPT that a highly aerated soil that supports little or no perched water will be much easier to produce healthy plants in. Many will point out there is more than one way to skin a cat, to which we can reply, "Yes, but there are still good ways and bad ways, easier ways and more difficult ways to skin that cat."


  • PRO

    Happy Easter Everyone!

  • jenn

    Happy Easter to you, Al.

    The photo above is very helpful in presenting the correct size for the bark pieces. Thanks!

  • newgen

    Al (or anyone else growing container citrus): with the gritty mix, do you use only the Foliage Pro as fertilizer, and nothing else?


  • hayden2

    Al, thank you. Your answers may be harder than "oh, just go to X store and buy Y", but you are so practical and common sensical, I really appreciate it. I'll give it a shot. Where I live, people are more apt to know the best deli than to know chicken grit, however !! And in the country side closest to here, they are more inclined to cook livestock in some fancy french recipe, than to raise it. But we'll see, someone might surprise me.

    PS - Happy Easter to all who celebrate!!

  • PRO

    Foliage-Pro is all you need, but I do include a little ProTeKt 0-0-3 each time I fertilize.

    Hayden - I understand the issues associated with finding anything in a rural setting where you live are particularly difficult. I've helped a lot of folks find ingredients by getting on the phone myself (Houston & Virginia Beach being a couple of the more recent), but I don't know where I'd even begin in New York. One thing you might try is contacting a local bonsai club and asking them about these ingredients. If you get a live person to talk to, you might ask for the email address of the club's most knowledgeable 'soil' person. EVERY club has one. ;o)

    Thanks Jenn, and Hayden - for the Easter wishes. I'm not only the gardener around here; I'm the cook, too. We had a houseful of extended family today - even including my wife's X and his mother - Lol. Not many people can say that, I bet. ;-) Everyone just cleared out a little while ago - looooooong day, but fun.


  • jodik_gw

    Bump! :-)

    Can't allow this one to slip into obscurity! It's very important! :-)

  • PRO

    Thanks, Jodi. ;-)


  • organic_wonderful

    I have two questions:

    1. For the gritty mix, I've found a supplier that sells 'turkey flint grit'. Will this be okay to use for the gritty mix?

    2. I'm growing a variety of fig called Califfo Blue. Will it grow well in the gritty mix or would you make any alterations to the mix?

  • TheMasterGardener1

    I have done a look at home depot for some pine bark fines and could not find. They had multch, pink bark but not fine. Should I check my local garden center?

  • greenman28 NorCal 7b/8a

    Yes, check your garden center.

    I often use "Orchid Bark" in *fine* grade, which still requires screening.
    E.B. Stone also packages a product called Greenall Micro Bark that is essentially
    the same as their Orchid Bark (fir), but in a larger bag and costing much less.

    Availability of proper bark is often a regional/seasonal thing. In California,
    we're quite spoiled with the massive amount of Douglas Fir.

    Where do you live, Master Gardener?
    There are many Threads devoted to sourcing ingredients.


  • PRO

    OW - 1) If the mix is inert (with no added solubles) and in the right size range (both important considerations), it should be fine.

    2) I haven't yet seen any plant in the Ficus genus (or any other tree or woody plant) that didn't LOVE the gritty mix.

    MG - what Josh said. Your user info doesn't give a clue to where you live (would be helpful), but the PBFs are sort of where you find them. I can sometimes find them at big box stores, but I have other reliable sources I've ferreted out that I can rely on to always come through. It sometimes takes a little initial effort, but don't give up, and please don't just 'settle' for something you're not sure will work.


  • Waryap

    I understand why the Gritty Mix is preferred over the 5:1:1 when it comes to perennials (doesn't break down as quickly). Is there an advantage to using the 5:1:1 over the Gritty Mix when it comes to annuals? Is it just a matter of convenience and cost? Or is there something about annuals to where they perform better in the 5:1:1?


  • PRO

    It's not a question of performance, as I've only found 1 fairly obscure plant that, for some unknown reason, seems to be happier in the 5:1:1 than in the gritty mix. The only advantages in using the 5:1:1 mix is it's easier to make and the ingredients are usually easier to locate. All but the 1 plant (a Scilla) I've found that prefers the 5:1:1 mix do better in the gritty mix ...... but you DO need to stay on top of your fertilizing game. ;-)


  • jodik_gw

    Bump! :-)

  • jodik_gw

    Very big... BUMP!!!

    (How the heck did this important bit of information get buried on the fourth page?!)

  • PRO

    Lol - it happens ...... then someone stumbles on it & it ends up back on the face page. ;-) Thanks, Jodi.


  • cincy_garden

    Hi Al,

    I haven't seen this discussed before, at least in this fashion. My questions are ONLY about the particles size.

    I understand the generic version as:
    Turface, Floor-Dry, Gran-I-Grit size ranges from 1/16 to 1/4 inch
    Fir Bark size ranges from 1/8 to 1/4 inch
    Pine Bark size ranges from 1/8 to 3/8 inch
    with Turface & Floor-Dry; Fir Bark & Pine Bark interchangeable

    I got the following sizes available: more details here
    Turface 1/16 to 1/8 inch
    Turface 1/8 to 1/4 inch
    Gran-I-Grit 1/16 to 1/8 inch
    Gran-I-Grit 1/8 to 1/4 inch

    I am wondering, Is there any scope to improve Gritty mix by *narrowing* down the particles size?

    With Turface (& Gran-I-Grit), I noticed the ratio of individual particles size (1/16 to 1/8) : (1/8 to 1/4) is not exactly 1:1 out of the bag.

    Does consistent particles size improves the quality of mix?

    Would you recommend to go with ONLY 1/8 to 1/4 inch particles size of Turface (& Gran-I-Grit) instead of 1/16 to 1/4? In that way it would be similar to Fir Bark size.


    Would you recommend to go with 1:1 ratio particles size (1/16 to 1/8) : (1/8 to 1/4) for Turface (& Gran-I-Grit) instead of out-of-the-bag ratio?


    Would you recommend different ratio of particles size (1/16 to 1/8) : (1/8 to 1/4) for Turface (& Gran-I-Grit)?

    Irrelevant of ratio of individual particles size I will be sticking to 1:1:1 ratio of overall mix.

    In the interest of plants, I am not considering the following:
    In case if any of the following changes because of specific ratio of particles size.
    Final mix being expensive
    Wastage after screening
    Labour on screening
    Keeping up with fertigation
    Weight of the final mix

    I am going to use the ratio of 1:1:1 = Turface : Gran-I-Grit : Fir Bark, though I understand it can be tailored.

    For now, I am planning to use one kind of Gritty mix for all of my plants.

    The following are taken "out of context", so it is not to support/disprove anything, but just to say that there is too much info on particles size to read and understand.

    A particle size of just under 1/8 (3/32) to 3/16 would be ideal.
    You want the aggregate size to be in the 1/16 - 3/16 size, with most of the particulates favoring the 1/16 - 1/8 size range.
    The trick is to get as many of the soil particles in that 1/16-3/32 range as possible. Just be sure the particle size is 1/16 inch +.
    As soil particulate size approaches 1/8", the level of perched water in the container approaches 0.
    crushed granite in a 1/16 - 3/16" size range in its stead.
    We know that there is an inverse relationship between soil particle size and the height of the PWT in containers. As particle size increases, the height of the PWT decreases, until at about a particle size of just under 1/8 inch, soils will no longer hold perched water.
    The soils I grow in are all comprised of particles in roughly the 1/16 to 1/4" size, (if the bark is between 1/16 - 1/4") with the largest measure occupying a range from about 3/32 - 3/16".
    'ideal' bark size would be 1/8-1/4"
    1/8-3/8 is best for the gritty mix.
    inorganic fraction of the gritty mix would be in the 1/10-1/8" size range
    You could actually use everything that goes through a 3/8 or even a 1/2" screen.
    fir bark, which is 'chunkier' than pine bark, use 1/8-1/4" if you can. pine bark, which is flatter than fir bark, use what passes through 3/8 but not 1/8".


  • jodik_gw

    And another bumpity-bump-bump! :-)

    I wish there were a way to make this a permanent part of page 1... I think it would be incredibly helpful to so many gardeners!

  • rdak

    I have used Al's mixes for a few years now and they are great.

    But, I notice ALOT of mention is made about getting the PROPER sized pine bark.

    I have always used pine bark mulch with some pieces in the bag that are larger than optimal (because it is hard for me to find the small sizes).

    Yet, I have never had any problems with pine bark, even if it is "too" big.

    Why is it so important to use small sized pine bark. Most of the bags I use are a mix of larger than optimal sized bark with chunks that are optimal sizes.

    (Those types of pine bark mulch bags are everywhere where I live......so I use those. And, I assume, these types of "mixed" sized pine bark bags are available for all of us here.) )

    I don't screen them, yet the mix always performs very well.

    Are we making too much of a fuss on the exact sized pine bark that is needed?

    (Just don't use the big nuggets though.)

    I've always been a bit puzzled on this area of the proper pine bark size.

    For me, as long as you don't use the nugget size and just buy the typical pine bark mulch bags.......they work REAL WELL.

    Like I said, I've always been a little puzzled on this one?

  • esebastian

    I am new to this thread and have been reading and learning a lot for the last few days. Al, your 2 soil recipes sound scientific and logically make perfect sense that they would help with aeration and good drainage and I can't wait to mix my own. I have been trying to read as many of these threads as possible in a short time and I see how generous and more importantly patient you are with all who are interested and willing to learn your proven methods. I am trying to locate the ingredients here in NEPA and the only question that I have is the size of the pine for 5.1.1. and the gritty mix. Are they the same size or the gritty mix needs to be smaller. I know you and other generous members have answered this question in many other ways and I apologize to ask again. You have renewed my interest in plants and planting with your soils and success stories I have been reading in these threads. Your generosity in sharing your immense knowledge is unbelievable and your patience in helping others and answering questions is even more admirable. I hope I can learn more from you and the rest of the members here.

  • northraleighguy

    Hello Al - thanks again for all of your posts and the fruits of your research. I am growing four heirloom tomato plants in containers using your 5-1-1 mix. Here in Raleigh the closest thing I could find to pine bark fines was a product by Timberline called "Soil Conditioner" which seems to be close to the ideal size.

    But I wanted to ask you two questions, which I hope you have the time to answer (and patience, if you've already answered them - I looked and could not find your thoughts on these):

    1. I used a run of the mill mulch to top off my 5-1-1 mixes in the pots and to my dismay discovered the mulch was full of fungus gnats. I will try Gnatrol to get rid of them, but it brings up my question - what do you use for mulch for the 5-1-1? Maybe pine bark nuggets instead of this buggy shredded hardwood I'm using? (large size might help to avoid insect eggs or other stuff hiding inside?) Or do you not mulch?

    2. And secondly, what do you use for day to day pest control? I'm spraying insecticidal soap almost daily to kill the whiteflies/thrips/aphids that I see on the leaves but I wonder if there's anything better I can do instead of using the toxic stuff (Sevin, etc).


  • cyn_s

    greentiger87 - you posted a suggestion back in April of a way to present Al's basic info that's awesome! It's EXACTLY what I've been looking for. I've spent lots and lots of time reading thru these posts - starting w/ the original one - and I realized when I went to bed at 2 am "last night" (just can't quit reading this stuff) that I still didn't understand all the particulars of Al's recommentations. Your summary is immensely helpful, so a big, big thank you.

    Ironically, the day after you posted this (unbeknowst to me) I started a post asking which of the two choices I've been able to locate - Garden Pro Soil Conditioner w/ Gypsum or Nature's Helper Soil Conditioner - would be preferable. (I tried searching for the answer before asking; but I've found that the search function isn't always reliable). Between the responses I got and the info I've found elsewhere on this forum I think NH is maybe better (altho on this thread Al recommended against it) - but neither are great.

    So does anyone know of anywhere in the Knoxville area I could get the right kind of fines?

  • Ohiofem

    On pine bark fines: not many retailers in my part of the world use the term pine bark fines, but many of them sell them under different names. I've found pine bark mulch that is suitable for the 5-1-1 mix from big box stores, hardware stores and independently owned garden centers. You just need to get your eyes on what's in the bag. The only place I've found in central Ohio that sells pbf as fines is Ohio Mulch. I've been using Tatman's Southern Line, which is labeled decorative ground cover in large letters across the front and pine bark mulch in smaller letters on the side. It seems perfect to me, with most particles under 1/4 inch in size.

    There is along thread with lots of info on where to find ingredients for Al's mixes by state that I'll link below.

    Here is a link that might be useful: Where to find ingredients, by state

  • esebastian

    greentiger87, Those are nice sieves that you posted pictures of uptread. Did you make them yourself? What are the dimensions if you don't mind sharing..

  • PRO

    Rdak - it's more important to have the "right size bark for the gritty mix than the 5:1:1 mix, but sizes that are too large reduce the volume in the container available for root colonization.

    Emmanuel - thank you for your kindness. ;-)

    NRG - I don't mulch anything - I like my containers to dry out quickly. What I use for insect control would be very dependant on the pest and whether or not what I was growing was table fare.

    Take care, guys.


  • cyn_s

    Ohiofem - thanx for the link. Unfortunately there's nothing on there for TN, Tennessee, or Knoxville. I realize most people - retailers included - have no idea what "pine fines" are; I usually ask first for soil conditioners. I lucked out w/ both the Natures' Helper and the Garden Pro when knowledgeable "kids" at Lowe's and Home Depot knew what they were composed of. But those are the only options I've been able to find.

    Lrvjim gave me some very helpful info on my "Which Soil Conditioner?" post: it looks like the NH will work! So hopefully I'm set, altho I always appreciate any recommendations.

    Thanx again.

  • PRO

    You will find the thread continued (part XIV) if you follow the link below.

    Here is a link that might be useful: Click me and I'll take you to the continuation

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