Tapla's 5-1-1 Container Mix in More Detail

February 26, 2009

I recently joined the forum and discovered Al's 5-1-1 Mix, but I had several questions that Al was kind enough to answer by email. I also found the answers to other questions in several different threads. I thought it would be useful to organize all of the info in one place so that we could have easy access to it. 98% of the following has been cut/pasted from Al's postings, and I apologize in advance if I have somehow misquoted him or taken his ideas out of proper context. The only significant addition from another source is the Cornell method of determining porosity, which I thought would be germane. I have used a question and answer format, using many questions from other members, and I apologize for not giving them proper credit. Thanks to all who contributed to this information. Now, here's Al:

Tapla's 5-1-1 Mix

5 parts pine bark fines

1 part sphagnum peat

1-2 parts perlite

garden lime

controlled release fertilizer (not really necessary)

a micro-nutrient source (seaweed emulsion, Earthjuice, Micro-max, STEM, etc,)

Many friends & forum folk grow in this 5-1-1 mix with very good results. I use it for all my garden display containers. It is intended for annual and vegetable crops in containers. This soil is formulated with a focus on plentiful aeration, which we know has an inverse relationship w/water retention. It takes advantage of particles, the size of which are at or just under the size that would guarantee the soil retains no perched water. (If you have not already read Al's treatise on Water in Container Soils, this would be a good time to do so.) 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 starve/"suffocate" because there is insufficient air at the root zone to ensure normal water/nutrient uptake and root function.

I grow in highly-aerated soils with the bulk of the particles in the 1/16"-1/8" size, heavily favoring the larger particles, because we know that perched water levels decrease as particle size increases, until finally, as particle size reaches just under 1/8" the perched water table disappears entirely.

Ideal container soils will have a minimum of 60-75% total porosity. This means that when dry, in round numbers, nearly 70% of the total volume of soil is air. The term 'container capacity' is a hort term that describes the saturation level of soils after the soil is saturated and at the point where it has just stopped draining - a fully wetted soil. When soils are at container capacity, they should still have in excess of 30% air porosity. Roughly, a great soil will have about equal parts of solid particles, water, and air when the soil is fully saturated.

This is Cornell's method of determining the various types of porosity:

To ensure sufficient media porosity, it is essential to determine total porosity, aeration porosity, and water-holding porosity. Porosity can be determined through the following procedure:

* With drainage holes sealed in an empty container, fill the container and record the volume of water required to reach the top of the container. This is the container volume.

* Empty and dry the plugged container and fill it with the growing media to the top of the container.

* Irrigate the container medium slowly until it is saturated with water. Several hours may be required to reach the saturation point, which can be recognized by glistening of the medium's surface.

* Record the total volume of water necessary to reach the saturation point as the total pore volume.

* Unplug the drainage holes and allow the water to freely drain from the container media into a pan for several hours.

* Measure the volume of water in the pan after all free water has completed draining. Record this as the aeration pore volume.

* Calculate total porosity, aeration porosity, and water-holding porosity using the following equations (Landis, 1990):

* Total porosity = total pore volume / container volume

* Aeration porosity = aeration pore volume / container volume

* Water-holding porosity = total porosity - aeration porosity

The keys to why I like my 3-1-1 mix:

It's adjustable for water retention.

The ingredients are readily available to me.

It's simple - 3 basic ingredients - equal portions.

It allows nearly 100% control over the nutritional regimen.

It will not collapse - lasts longer than what is prudent between repots.

It is almost totally forgiving of over-watering while retaining good amounts of water between drinks.

It is relatively inexpensive.

Q. Why do you use pine bark fines? Bark fines of fir, hemlock or pine, 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 natures 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.

Q. What is the correct size of the fines? 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 starve/"suffocate" because there is insufficient air at the root zone to insure normal water/nutrient uptake and root function.Pine bark fines are partially composted pine bark. Fines are what are used in mixes because of the small particle size. There will be a naturally occurring "perched water table" (PWT) in containers when soil particulate size is under about .125 (1/8) inch, so best would be particulates in the 1/16 - 3/16 size range with the 1/16-1/8 size range favored.

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 ½ BB size I leave it out of soils. Compost is too unstable for me to consider using in soils. The small amount of micro-nutrients it supplies can easily be delivered by one or more of a number of chemical or organic sources.

Q. Do you use partially composted pine bark fines? Yes - preferred over fresh fines, which are lighter in color.

Q. I found some Scotchman's Choice Organic Compost, which is made of pine bark fines averaging about 1/8" in size, and, after adding all ingredients, the 5-1-1 Mix had a total porosity of 67% and an aeration porosity of 37%. Is that all right? Yes, that is fine.

Q. What kind of lime do you use? Dolomitic.

Q. What amount of lime should I add if I used 10 gal of pine bark fines and the corresponding amount of the other ingredients? @ 5:1:1, you'll end up with about 12 gallons of soil (the whole is not equal to the sum of the parts when you're talking about soils), so I would use about 10-12 Tbsp or 2/3-3/4 cup of lime.

Q. What grade of coarseness for the lime? Most is sold as garden lime, which is usually prilled powder. Prilling makes it easier to use in drop & broadcast spreaders. The prills dissolve quickly. The finer the powder the quicker the reactive phase is finished. Much of the Ca and Mg will be unavailable until the media pH equalizes so the plant can assimilate the residual elements. Large pieces of lime really extend the duration of the reactive phase.

Q. Does this mean that I need to make up the soil in advance? Yes. 2 weeks or so should be enough time to allow for the reaction phase to be complete & residual Ca/Mg to become more readily available from the outset .

Q. During those 2 weeks, do I need to keep turning it and moistening it? No

Q. Can I go ahead and fill my 3-gal. containers, stack them 3-high, and cover the top one to prevent moisture loss during the waiting period? Something like that would be preferred.

Q. The perlite I use has a large amount of powder even though it is called coarse. Do I need to sift it to get rid of the powder? Not unless it REALLY has a lot - then, the reason wouldn't be because of issues with particle size - it would be because you had to use larger volumes to achieve adequate drainage & larger volumes bring with it the possibility of Fl toxicity for some plants that are fluoride intolerant.

Q. What about earthworm castings (EWC)? I think 10% is a good rule of thumb for the total volume of fine particles. I try to limit peat use to about 10-15% of soil volume & just stay away from those things that rob aeration & promote water retention beyond a minimal perched water table. If you start adding 10% play sand, 10% worm castings, 10% compost, 10% peat, 10% topsoil, 10% vermiculite to a soil, before long you'll be growing in something close to a pudding-like consistency.

Q. Do you drench the mix with fertilized water before putting in containers? No - especially if you incorporate a CRF. It will have lots of fertilizer on it's surface & the soil could already be high in solubles. If you added CRF, wait until you've watered and flushed the soil a couple of times. If you didn't use CRF, you can fertilize with a weak solution the first time you water after the initial planting irrigation.

Q. How much of the micronutrients should I add if I am going to be fertilizing with Foliage Pro 9-3-6, which has all the micronutrients in it? You won't need any additional supplementation as long as you lime.

Q. Just to make sure I understand, are you saying I don't need to use Foliage Pro 9-3-6 until after the initial watering right after planting even if I don't use a CRF? And no additional micronutrients? That's right - on both counts.

Q. Do I need to moisten the peat moss before mixing with the pine bark fines? It helps, yes.

Selections from Notes on Choosing a Fertilizer

A) Plant nutrients are dissolved in water

B) The lower the nutrient concentration, the easier it is for the plant to absorb water and the nutrients dissolved in the water - distilled water is easier for plants to absorb than tap water because there is nothing dissolved in distilled water

C) The higher the nutrient content, the more difficult it is for plants to absorb water and the nutrients dissolved in water

D) To maximize plant vitality, we should supply adequate amounts of all the essential nutrients w/o using concentrations so high that they impede water and nutrient uptake.

All that is in the "Fertilizer Thread" I posted a while back.

Q. Do you use the Dyna-Gro Foliage Pro 9-3-6 exclusively throughout the life of the plant, or change to something else for the flowering/fruiting stage? I use lots of different fertilizers, but if I had to choose only one, it would likely be the FP 9-3-6. It really simplifies things. There are very few plants that won't respond very favorably to this fertilizer. I use fast soils that drain freely & I fertilize at EVERY watering, and it works extremely well.

If you are using a soil that allows you to water freely at every watering, you cannot go wrong by watering weakly weekly, and you can water at 1/8 the recommended dose at every watering if you wish with chemical fertilizers.

Q. What about the "Bloom Booster" fertilizers? To induce more prolific flowering, a reduced N supply will have more and better effect than the high P bloom formulas. When N is reduced, it slows vegetative growth without reducing photosynthesis. Since vegetative growth is limited by a lack of N, and the photosynthetic machinery continues to turn out food, it leaves an expendable surplus for the plant to spend on flowers and fruit. There are no plants I know of that use anywhere near the amount of P as they do N (1/6 is the norm). It makes no sense to me to have more P available than N unless you are targeting a VERY specific growth pattern; and then the P would still be applied in a reasonable ratio to K.

Somewhere along the way, we curiously began to look at fertilizers as miraculous assemblages of growth drugs, and started interpreting the restorative effect (to normal growth) fertilizers have as stimulation beyond what a normal growth rate would be if all nutrients were adequately present in soils. ItÂs no small wonder that we come away with the idea that there are Âmiracle concoctions out there and often end up placing more hope than is reasonable in them.

What I'm pointing out is that fertilizers really should not be looked at as something that will make your plant grow abnormally well - beyond its genetic potential . . . Fertilizers do not/can not stimulate super growth, nor are they designed to. All they can do is correct nutritional deficiencies so plants can grow normally.

Q. Should I use organic ferts or chemical ferts in containers? Organic fertilizers do work to varying degrees in containers, but I would have to say that delivery of the nutrients can be very erratic and unreliable. The reason is that nutrient delivery depends on the organic molecules being broken down in the gut of micro-organisms, and micro-organism populations are boom/bust, varying widely in container culture.

Some of the things affecting the populations are container soil pH, moisture levels, nutrient levels, soil composition, compaction/aeration levels ..... Of particular importance is soil temperatures. When container temperatures rise too high, microbial populations diminish. Temps much under 55* will slow soil biotic activity substantially, reducing or halting delivery of nutrients.

I do include various formulations of fish emulsion in my nutrient program at certain times of the year, but I never rely on them, choosing chemical fertilizers instead. Chemical fertilizers are always immediately available for plant uptake & the results of your applications are much easier to quantify.

Q. Should I feed the plants every time I water? In a word, yes. I want to keep this simple, so IÂll just say that the best water absorption occurs when the level of solutes in soil water is lowest, and in the presence of good amounts of oxygen. Our job, because you will not find a sufficient supply of nutrients in a container soil, is to provide a solution of dissolved nutrients that affords the plant a supply in the adequate to luxury range, yet still makes it easy for the plant to take up enough water to be well-hydrated and free of drought stress. All we need to do is supply nutrients in approximately the same ratio as plants use them, and in adequate amounts to keep them in the adequate to luxury range at all times. Remember that we can maximize water uptake by keeping the concentrations of solutes low, so a continual supply of a weak solution is best. Nutrients donÂt just suddenly appear in large quantities in nature, so the low and continual dose method most closely mimics the nutritional supply Mother Nature offers. If you decide to adopt a "fertilize every time you water" approach, most liquid fertilizers can be applied at ¾ to 1 tsp per gallon for best results.

The system is rather self regulating if fertilizer is applied in low concentrations each time you water, even with houseplants in winter. As the plantÂs growth slows, so does its need for both water and nutrients. Larger plants and plants that are growing robustly will need more water and nutrients, so linking nutrient supply to the water supply is a win/win situation all around.

You can tell you've watered too much (or too little - the response is the same - a drought response) when leaves start to turn yellow or you begin to see nutritional deficiencies created by poor root metabolism (usually N and Ca are first evident). You can prevent overwatering by A) testing the soil deep in the container with a wood dowel ... wet & cool - do not water, dry - water. B) feeling the wick & only watering when it's dry C) feel the soil at the drain hole & only water when it feels dry there.

Soils feel dry to our touch when they still have 40-45% moisture content. Plants, however, can still extract water from soils until they dry down to about 25-30%, so there is still around a 15% cush in that plants can still absorb considerable moisture after soils first feel dry to us.

Q. When you water/fertilize, do you give it enough that 10% leaches out the bottom each time? Yes, I try to do that at every watering. Remember that as salts accumulate, both water and nutrient uptake is made more difficult and finally impaired or made impossible in severe cases. Your soils should always allow you to water so that at least 10-15% of the total volume of water applied passes through the soil and out the drain hole to be discarded. This flushes the soil and carries accumulating solutes out the drain hole. In addition, each thorough watering forces stale gases from the soil. CO2 accumulation in heavy soils is very detrimental to root health, but you usually can't apply water in volume enough to force these gases from the soil. Open soils allow free gas exchange at all times.

Q. Should I elevate my pots? The container will not drain the same % of water if it's sitting in a puddle, but the % won't be particularly significant. What will be significant is: if water (in a puddle) is able to make contact with the soil in the container through surface tension and/or capillarity, it will "feed" and prolong the saturated conditions of any PWT that might be in the container. However, if water can soak in or if it will flow away from the containers, there's no advantage to elevating when you're not using a wick.

Q. I like a pH of about 5.7. Is that about right? That's a good number, but you won't have any way of maintaining it in your soil w/o some sophisticated equipment. I never concern myself with media pH. That doesn't mean you should ignore water pH, though. It (water pH) affects the solubility of fertilizers; and generally speaking, the higher the water pH, the lower the degree of nutrient solubility.

Q. How do you repot? Some plants do not take to root-pruning well (palms, eg), but the vast majority of them REALLY appreciate the rejuvenational properties of major root work. I'm not at all delicate in my treatment of rootage when it comes time to repot (completely different from potting-up). Usually I chop or saw the bottom 1/2-2/3 of the root mass off, bare-root the plant, stick it back in the same pot with ALL fresh soil, use a chopstick to move soil into all the spaces/pockets between roots, water/fertilize well & put in the shade for a week to recover. I should mention that this procedure is most effective on plants with woody roots, which most quickly grow to be inefficient as they lignify, thicken, and fill the pot. Those plants with extremely fibrous root systems are easier to care for. For those, I usually saw off the bottom 1/2 - 2/3 of the roots, work a chopstick through the remaining mat of roots, removing a fair amount of soil, prune around the perimeter & repot in fresh, well-aerated soil.

I find that time after time, plants treated in this fashion sulk for a week or two and then put on a huge growth spurt (when repotted in spring or summer). Growth INVARIABLY surpasses what it would have been if the plant was allowed to languish in it's old, root-bound haunts. Potting up is a temporary way to rejuvenate a plant, but if you look ate a long-term graph of plants continually potted-up, you will see continual decline with little spurts of improved vitality at potting-up time. This stress/strain on plants that are potted-up only, eventually takes its toll & plants succumb. There is no reason most houseplants shouldn't live for years and years, yet we often content ourselves with the 'revolving door replacement' of our plants when just a little attention to detail would allow us to call the same plant our friend - often for the rest of our lives if we prefer.

Q. Is there any rule of thumb as to how often to root prune? I'm going to answer as if you included 'repotting' in your question. There is no hard, fast rule here. Some of you grow plants strictly for the blooms, and some plants produce more abundant blooms in containers when they are stressed in some manner. Often, that stress is in the form of keeping them root-bound. I'll talk about maintaining a plant's vitality & let you work out how you want to handle the degree of stress you wish to subject them to, in order to achieve your goals. Before I go on, I'd like to say that I use stress techniques too, to achieve a compact, full plant, and to slow growth of a particularly attractive plant - to KEEP it attractive. ;o) The stress of growing a plant tight can be useful to a degree, but at some point, there will be diminishing returns.

When you need to repot to correct declining vitality:

1) When the soil has collapsed/compacted, or was too water-retentive from the time you last potted-up or repotted. You can identify this condition by soil that remains wet for more than a few days, or by soil that won't take water well. If you water a plant and the soil just sits on top of the soil w/o soaking in, the soil has collapsed/compacted. There is one proviso though: you must be sure that the soil is wet before you assess this condition. Soils often become hydrophobic (water repellent) and difficult to rewet, especially when using liquid organic fertilizers like fish/seaweed emulsions. Make sure this effect is not what you're witnessing by saturating the soil thoroughly & then assessing how fast the water moves downward through the soil. The soils I grow in are extremely fast and water disappears into the mix as soon as it's applied. If it takes more than 30 seconds for a large volume of water to disappear from the surface of the soil, you are almost certainly compromising potential vitality.

I'll talk about the potential vitality for just a sec. Plants will grow best in a damp soil with NO perched water. That is NO saturated layer of water at the bottom of the pot. Roots begin to die a very short time after being subjected to anaerobic conditions. They regenerate again as soon as air returns to the soil. This cyclic death/regeneration of roots steals valuable energy from the plant that might well have been employed to increase o/a biomass, and/or produce flowers and fruit. This is the loss of potential vitality I refer to.

2) When the plant is growing under tight conditions and has stopped extending, it is under strain, which will eventually lead to its death. "Plants must grow to live. Any plant that is not growing is dying." Dr. Alex Shigo Unless there are nutritional issues, plants that have stopped extending and show no growth when they should be coming into a period of robust growth usually need repotting. You can usually confirm your suspicions/diagnosis by looking for rootage "crawling" over the soil surface and/or growing out of the drain hole, or by lifting the plant from its pot & examining the root mass for encircling roots - especially fat roots at the container's edge. You'll be much less apt to find these types of roots encircling inner container perimeter in well-aerated soils because the roots find the entire soil mass hospitable. Roots are opportunistic and will be found in great abundance at the outside edge of the soil mass in plantings with poor drainage & soggy soil conditions - they're there looking for air.

3) When the soil is so compacted & water retentive that you must water in sips and cannot fully flush the soil at each watering for fear of creating conditions that will cause root rot. This isn't to say you MUST flush the soil at every watering, but the soil should drain well enough to ALLOW you to water this way whenever you prefer. This type of soil offers you the most protection against over-watering and you would really have to work hard at over-fertilizing in this type of soil. It will allow you to fertilize with a weak solution at every watering - even in winter if you prefer.

Incidentally, I reject the frequent anecdotal evidence that keeping N in soils at adequacy levels throughout the winter "forces" growth or "forces weak growth". Plants take what they need and leave the rest. While there could easily be the toxicity issues associated with too much fertilizer in soils due to a combination of inappropriate watering practices, inappropriate fertilizing practices, and an inappropriate soil, it's neither N toxicity NOR the presence of adequate N in soils that causes weak growth, it's low light levels.

Q. Is there any rule of thumb as to how often to remove and replace the old soil? Yes - every time you repot.

As always, I hope that those who read what I say about soils will ultimately take with them the idea that the soil is the foundation of every container planting & has effects that reach far beyond the obvious, but there is a snatch of lyrics from an old 70's song that might be appropriate: "... just take what you need and leave the rest ..." ;o)

Comments (282)

  • newhostalady Z6 ON, Canada

    " Ideal size range for 5:1:1 is dust to 3/8"

    Does that mean you can use bark which is all dust, or all 3/8" pieces, or any combination of bark in those sizes when making a batch of 5:1:1?

  • tropicofcancer (6b SW-PA)

    No you cannot use all dust - it will have very high PWT - means saturated with water with no air space. Just like a fine sponge. Remember that thin layer of water on particles I talked about before? The small particles will have large surface area to support that thin layer of water and capillary forces will be very high pushing water through those minute air spaces making them saturated. Opposite is true for all large particles - lots of air spaces and very little water holding capacity.

    Imagine a bottle filled with say 3/8 inch diameter marbles. There will be lots of air spaces between the marbles. In fact too big air spaces. Now add a bunch of smaller marbles that exactly fit the air spaces in between the marbles. This will reduce the gaps between marbles considerably, right. Now add some marbles that fit exactly in those air spaces - and so on.

    To get an idea how it works here is an image found on wikipedia to illustrate:

    So to reduce the air space you need smaller marbles and each time you do that that thin layer of water on particles come closer. If they are too close capillary action will draw water up through those spaces.

    Notice how you need more of the smaller particles to pack in between. Actually, the volume of the larger ones is larger but the number is smaller. As you get smaller in size the volume needed is smaller but the number of particles is larger.

    So what is the right proportion - hard to tell and hard to control. I normally sift out anything below 1/8 inch first. Then add about some back so that it is about 15% by volume of the total mix.

  • newhostalady Z6 ON, Canada

    Thanks for taking the time to explain in more detail. It is really helping me, and I think others, to understand what happens in different sized media. Great image you found there to demonstrate.

  • tropicofcancer (6b SW-PA)

    My example is a simplification using an ideal scenario but helps to explain. Reality tends to be different.

    For one, bark is essentially flattish (fir bark is less so) and has a tendency to lay flat on each other. This effectively makes it quite a compact stack with much less air space - called stratification. Here is where more spherical particles like perlite/pumice/turface plays a big role in preventing that stacking and encouraging more random orientation of the bark in the mix.

    If you search for circle/sphere packing you will find it is a hot research topic. That is how I got the image. Nothing much to do with soil though. It is important in inventing exotic materials and a mathematical curiosity.

  • newhostalady Z6 ON, Canada

    I understand. Your explanation is a simplified version. I think that is the best way for new people (like me) to understand these concepts. You start off simple and then move on to more complex principles.

    It's wonderful that you have taken your time to explain the above for me and others interested.

  • mblan13

    Another example would be in bonsai soil. High mountain pines require less water than lowland species and deciduous trees like Japanese maples that grow in soil, rather than little pockets of organic matter in rock crevasses.

    So when potting a mountain pine it's recommended to use 1/4 to 3/8 inch particles, but for lowland species they will recommend 1/8 to 1/4 and ones that do better in very moist soil 1/16 to 1/8.

    So the smaller the soil particulate the more water it will hold.

  • mblan13

    I like to use Bonsai soil as an example. High mountain pines that require less water get a soil that consists of 1/4 to 3/8 particles, lowland pines or deciduous 1/8 to 1/4, and ones that like wetter soils 1/16 to 1/8. So the smaller the particles, the more water they will retain...Easy Peasy!

  • Vladimir (Zone 6a Massachusetts)

    Tropic. Regarding the proportion of pine bark dust, it varies from lot to lot and depends on how long the mulch has been lying around and so is quite variable.

    I normally sift out anything below 1/8 inch first. Then add about some back so that it is about 15% by volume of the total mix.

    I have been trying to get this information from Al but he has evaded answering my question.

  • tropicofcancer (6b SW-PA)

    Vladimir: That is the reason I sift out 1/8 or less (call it fines) first and mix it back in controlled quantity. If the bark looks out of proportion on the high side I will also sift out greater than 1/4 and mix back some of the 1/4-1/2 (call it chunks) back for 511. I wish I had a 3/8 screen. Having done this for quite a while I mostly eyeball it. When repotting if I feel I need to adjust for a particular plant I use bark fines, bark chunks and perlite to adjust it a bit. I treat the original recipe as starting concept and play around with it.

  • newhostalady Z6 ON, Canada

    "So the smaller the particles, the more water they will retain...Easy Peasy!"

    I have rooted some coleus in water. I do have some smaller bark sizes like 1/16 to 1/8th. And I think coleus like their water. So potting them using the smaller bark pieces in 5:1:1 will make for a media that will retain more water? I also read somewhere in the forum that the addition of turface increases water retention. The ratio being 5:1:1 plus 1 of turface. True?

  • PRO

    Vlad - do you think claiming I'm evading you and donning the mantle of victim as a result my sloth for not ensuring you have an understanding of the nuances associated with soil science is an appropriate way of venting your frustration? My brother, also my partner, is dying. That comes with a lot of emotional freight, and it essentially doubles my work load to the point I'm presently working 60 or more hours every week. Helping folks on the forums is an uplifting part of my personal growing experience; but simply put, it's more uplifting to share with people who don't chide me, as you've done on numerous occasions, because they feel entitled to attention I'm sometimes unable to provide.

    If/when you've gained a working understanding of the concept that drives water retention, you won't have need to ask these questions over and over because the answers will become obvious. You've been around these forums for a good long time - far longer than what would normally be required to gain an understanding of what drives water retention. Except where I think my replies might be of value to others who might be following the thread, I'm probably going to let someone else field your questions because there isn't much I can do to help you, lacking the basics. If you're unable to understand the concept, it's not going to do good in any measure if I repeat answers to the same questions from the same person in audio-loop fashion.

    NHL - I think what you suggest is something of an over-simplification. If we except cacti and succulent aficionados, probably 90-95% of the plants we most commonly grow in containers all prefer roughly the same type of environment for their roots. They want a soil with particles large enough that limiting amounts of water do not collect in the spaces between particles. It may seem perfectly reasonable to assume some plants LIKE moisture more than others, but in most cases, it's more accurate that some plants TOLERATE high moisture levels better than others.

    Smaller particles have the POTENTIAL to hold more water than larger particles, but picture in your mind's eye a jar of BBs, and a jar of Turface, Calcined DE, Pumice, or perlite that consists of particles twice the size of BBs. Which holds more water - the BBs or the other materials?

    Where soil particles are uniform in size, soils start to retain perched water as particle size diminishes to something less than .100" (1/10 of 1"). The smaller the particles become, the greater the potential for water retention. The smaller the volume of perched water a soil holds, the greater the potential for maximized root health. A worthy goal to work toward for most plantings is a soil that maximizes water retention while minimizing perched water's presence. This is accomplished by having a high % of internally porous particles in the size range of 1/10 to only slightly larger. In a perfect world, it would be particles .100-.125, but unless you have unlimited supplies and don't mind screening, this isn't realistic enough to make large numbers of growers interested in experimenting with highly aerated soils that hold little to no PW.


  • Vladimir (Zone 6a Massachusetts)

    Oh well, I give up trying to get an answer.

    I am truly sorry that your brother is dying and the difficult time you are having now. I know what it is like. Al, I wish you the best.

  • tropicofcancer (6b SW-PA)

    newhostalady: Coleus will be perfectly fine in 511. In early summer I directly root them in 511. In fact I root everything in 511. At the most I would sprinkle a thin layer of turface or bark fines, whichever is handy, on top of the mix for small cuttings.

  • newhostalady Z6 ON, Canada

    To Al:

    "Smaller particles have the POTENTIAL to hold more water than larger particles, but picture in your mind's eye a jar of BBs, and a jar of Turface, Calcined DE, Pumice, or perlite that consists of particles twice the size of BBs. Which holds more water - the BBs or the other materials?"

    The BBs!

    So here is what I understand:

    If the particles in a potting media are less than 1/10th of an inch, one will have a higher perched water table. This potting media will hold a lot of water. This will not be beneficial to the potted plant as the water will, in turn, rot roots and not allow a good supply of oxygen to the roots. So the goal would be to have a media that is 1/10th of an inch or slightly larger. This container media would maximize water retention but have the lowest perched water level possible. So the goal would be to have POROUS particles in the .100 to .125th size (of an inch)---or at least as close to that as possible---to give your container plants the best chance of health plant and root development!

    I hope I've got it! Thanks Al!

    Tropicofcancer, thanks for the information. I did root some coleus recently. I put some in water and some directly in potting medium. I bet 5:1:1 would have been a much better choice! Not sure the role of the turface or bark fines on top.

  • tropicofcancer (6b SW-PA)

    Turface or bark fines on top help to prevent the top drying out too quickly while the cuttings are rooting. Same is helpful when sprouting small seeds in 511.

  • newhostalady Z6 ON, Canada

    Great info. Going to make a note of that so I don't forget!

  • Conrad Todd

    Where do you guys get your bark at, and what is the name of the brand and size of the bark chunks, such as mini bark etc.? Also do you end up having to shift out a lot still or is it for the most part the right size when you get it? Thank you for your time guys.

  • newhostalady Z6 ON, Canada

    You might find this link helpful:

    Supplies by State/Region: Al's Gritty Mix

    It is helpful if you add the area you are from along with your name. Also best if you start your own thread. You may get more responses that way.

  • stuartlawrence (7b L.I. NY)

    Conrad Todd, I get my bark from Agways. Go to their website here and see if you have an Agway near you where you can order and buy it.

  • Dennis

    Could someone help me understand this portion:

    /quote/ There will be a naturally occurring "perched water table" (PWT) in containers when soil particulate size is under about .125 (1/8) inch, so best would be particulates in the 1/16 - 3/16 size range with the 1/16-1/8 size range favored. /quote/

    Shouldn’t larger particles be favored, hence the preferred size range should be LARGER than 1/8 inch (instead of 1/16-1/8)??

    Edit: Ahh! Got it now! I realise 1/16-1/8 inch is for 5/1/1 and not 1/1/1...

  • eric saga

    I cant believe I just read this entire thread...@tapla, you are a living legend! I said it a ffew days ago and I'll say it again! People are making and selling your gritty mix online! As I first began learning all this a few months ago, it made me pretty angry haha. Thank you to everyone who's helping amateurs like myself and others learn the importance of the foundation of growing! I was set on using the 511, but now I see I should be using the gritty mix for my plants. They are all basic indoor plants. Question...if using the gritty mix and constantly watering, is there a need for lime application since it will likely wash away?

  • tropicofcancer (6b SW-PA)

    Lime is primarily for adjusting the Ph of 511 mix. Peat is acidic and to some extent pine bark too. Secondary effect is to add Ca and Mg. Gritty does not need Ph adjustment since close to neutral to begin with. For gritty if you want to Ca you would need Gypsum (it is Ph neutral) and for Mg you need Epsom salt. But if your fertilizer already contains these then no need to add. Foliage Pro contains both and a host of micro nutrients too.
    If you have not used 511 or gritty before I would suggest to start with 511. You will have to repot (or at least up-pot) every 1-2 years. It is more forgiving mix and many plants will do well in it. It is also a lot lighter than gritty. Gritty or similar mix needs a little more learning. So I would say try it with succulents at least and some smaller woody plants first so that you can get used to it.

    If your plants are always indoors they would not need as frequent watering.

  • Saypoint 7a CT

    Can a peat-based potting mix be substituted for the peat in this mix? I would think it is water-retentive enough?

  • PRO

    Yes. That practice is/has been widely discussed and will work as well as or even better in certain cases than plain sphagnum peat moss (not to be confused with sphagnum moss). If you understand the principle that governs water retention in container media, you'll see (in your mind's eye) there must be a preponderance of large particles such that there is not enough fine material to fill all spaces between the fine particles. The state where there is exactly enough fines to fill all air spaces between the large particles is a threshold. In most instances, it will represent the worst soil that can be made with the two types (fine/coarse) of ingredients - PBFs and peat, for example. However, when you move from the threshold in the direction of a higher % of coarse ingredients and a smaller % of fine material, improvement in drainage and aeration happens very quickly, more so in mixes based on PBFs than most other materials. This is because a single piece of perlite or a small piece of pine bark wedged between 2 flat plates of coarse bark creates considerably larger pores than perlite mixed with peat, coir, compost, .......


  • ebfonehome

    I hope it is okay to comment on this thread. I am new to houzz discussions as well as plants. I apologize if this is the wrong spot for my question. I have been reading and re-reading any posts I can find about Al's mixes since I found out about them about 6 months ago. I have been trying to learn and understand as much as I can. Thank you Al for posting so prolifically and for making all this knowledge accessible to anyone who is searching. I have just gotten all the gritty mix ingredients and am in the process of sifting. I drove all the way to an Agways since people mentioned their pine bark mulch as a good option. My aloe and succulents have not been thriving in bagged mixes with perlite added. After reading Al's posts, I know why. I already made the 5:1:1 mix and I have a question about it. I am not sure if it has too much of the "dust" from the fines in it. I have let it sit for two weeks so I hope I can use it. I have seen differing answers and as much as I have tried to figure it out myself, I am at the point where I can only admit that I just don't know. Any help is appreciated.

  • eric saga

    Thank you @tropic! I have around 50 plants in the house, so I didnt want to repot them this year to do it again next year. I think its been discussed somewhere already, but if I mixed the pine bark and perlite for the 511 mix, and then add the peat based stuff on top, would that prolong the length between repotting? I'm imagining the fine particles taking twice the amount of time to make it down to the bottom and start compacting(which is the only reason it needs to be repotted, right?). @tapla can you or anyone else shine some light on that for me?

    Most of my plants are home depot and local nursery stuff...ponytail, yucca, corn palms, bird of paradise, money tree, weeping fig, flf, peace lily..etc etc..should I do the 511 mix for them over the gritty? I'll send pics of them when its daytime!

    I purchased most of the ingredients for both mixes last weekend, so should be able to use both. I ordered screens today as well. I realized without screening to proper size, lots of the effort will be wasted. I have about 20 more questions but I'll hold off for now haha. My wife and friends think I'm nuts, spending literally dozens of hours in this forum haha, but they will see once this soil is done!

    Sorry for the rambling and million questions! I feel like I see everyones reaction as similar upon discovering this next level soil info haha. I digested a good amount of this overwhelming amount of knowledge so far, and will continue reading every single thread haha. Thanks again everyone!


  • Saypoint 7a CT

    Thanks, re: using potting mix. That’s what I did when I mixed up 7 large totes of 5-1-1 last fall in anticipation of having fabulous containers this year. However, my containers are duds. We did have a wet spring, which set the annuals back a bit, but even now that the weather is hot and sunny, many of my container plantings are not looking good. I’m checking regularly for moisture with my fingers and feeding with a weak water soluble fertilizer every third watering or so. I pulled up a few plants yesterday and their root systems looked good, meaning they had spread well from their original quart nursery containers into the potting mix and looked healthy. I’m just not getting much growth up top. Not sure what I could be doing wrong. My containers in the past were full and lush with commercial bagged potting mix.

    Very disappointing, and I finally went out yesterday and bought a couple of large pre-planted hanging baskets and set them into my two main planters to replace the poor performers.

  • PRO

    While I can't dispute you're not happy with how your containers are performing, if there is inference it's caused by the 5:1:1 mix I'll point to the many hundreds of images of my own containers(dozens of images in this thread, if you're interested), in which I utilized the 5:1:1 mix, as assurance the potential for excellent results is inherent in a properly made 5:1:1 mix. The water I use has a pH much too high to be considered even fair; and, I don't do anything special other than water and fertilize appropriately.

    It's far more likely that: A) grower error is responsible B) there is a chemical problem with one or more of the ingredients, or C) the medium isn't formulated so you can take advantage of the superior aeration and drainage it offers. Examples of grower error would include not providing enough N, over-watering, the soil solution has a badly skewed nutrient ratio, your fertilizer lacks essential nutrients, .... A chemical problem with the ingredients could be bark from trees ponded in salt water, a bark pH crazy low because the bark was piled in wind rows and not turned. A poorly formulated soil would be one that has more than enough fine material to fill all air spaces between bark particles. If that occurs, you're actually in worse shape than you'd be had you simply grown in the fine materials and used a bigger pot with ballast at the bottom.

    So, there are many far more likely potentialities other than the the soil being a dud. If 100 or 10,000 can grow exceedingly well in any given medium, and one grower is having a problem, it's not logical to ask the formula (5:1:1) of the medium to bear the blame.

    FWIW, I freely discuss and bring to other's attention both the positive and negative considerations of using 5:1:1 or the gritty mix, and I'm not in the habit of defending either soil. It's my habit to try to keep things real any time I'm involved in a conversation, which is why I felt it important to make sure it's understood there is no problem whatsoever with the concept or the formulaic aspect of the 5:1:1 mix, so long as the formulaic aspect embodies the concept. It was never my intent to introduce growers to a rigid recipe; rather, I constantly stress there's far more to be gained by gaining an understanding of the concept.

    Let me know if you'd like to try to work through what limitation(s) is/are in play and see if we can't correct them. A good starting point would be an image of the dry finished 5:1:1 mix on a white sheet of paper, and images of the poor performers in their pots), + more info about how you fertilize/what you use (I strongly suspect a N deficiency because you have N immobilized by fresh bark.)


  • Skip1909

    I have a couple bags of fresh pine bark that have been sitting outside since April. I plan to soak it in water overnight before using it, will it require additional leaching? Should I add nitrogen or fertilizer to the soak water?

    I have had problems growing things in this bark and I think it was too fresh when I mixed it. Using more fertilizer as you recommended helped my holly cuttings a lot.

  • tropicofcancer (6b SW-PA)

    @ericsaga In 511 bark decomposes over time and that creates the finer particles and as it decomposes and it becomes more water retentive. Many here including me push out the repotting to later. Al, I think, religiously repots his plants in 511 every year. But I doubt he uses 511 for most of his plants that he overwinters for longer term. Some of my long-term plants are in 511 and I usually repot them after 2 seasons except a few that produce roots profusely and root congestion becomes a problem. Eg hibiscus is notorious in this department. Plants in smaller pots I will repot in a season. Bigger pots (say > 10 inches) I do it every other year. It is a pretty good mix that holds quite well. Note that my starting bark is also pretty fresh bark that tends to decompose slower. Real aged bark will be different. Mine is pseudo aged - I store my bark in a plastic barrel moist (with a bit of urea thrown in to provide some initial N) and use it in 4-6 months.

  • Vance Evans

    So the majority of bark in 511 should between 1/8" and 1/16"? Makes since and explains why my plants look sad when I initially pot in 511. My perlite is 1/8" to 1/2", and the majority of my bark is 1/8"-1/4." I've read this over and over for years, and I'm still learning. It's amazing how much you learn.

  • edweather USDA 9a, HZ 9, Sunset 28

    The bark size for the 511 mix is dust up to 3/8". Not sure why there is so much confusion about this basic fact. The gritty mix bark size is is more like 1/16-1/8 inch. If the bark tends to be a bit on the larger size and uncomposted, the peat can be increased to achieve the proper water retention. On the other hand, if the bark is a bit finer, and partially composted, the peat can be adjusted in the other direction.

  • Vance Evans

    True, but when I started reading this forum, I made my 511 from 1/2" to dust and didn't screen the fines. My batches were inconsistent because of the randomness in Pine bark sizes. So then I started screening fines and not putting enough of the fine material in the mix because I was thinking 1/8" was the end all be all for pw, not thinking about averages or medians for that sake. Now its clicking that the majority of the medium needs be right around that threshold, not much larger or smaller, the amount of the particle sizes should be a like a bell curve if it were graphed. I'm just saying I had an AHA moment in my last statement.

    Al has also stated that in gritty mix bark should be larger 1/8 - 3/8" due to the fact if will break down. The other two items should be between 1/16"-1/4."

    Again before this I thought 1/8" or .100" was the limit because anything below this would cause an issue with pw, now we more knowledge further clarification from Al, the books he's recommended to read, and a little common sense about averages being around that threshold (majority a little above and a little below).

  • tropicofcancer (6b SW-PA)

    Edweather: gritty mix bark is 1/8-1/4 inch.

    vance: I do not recall anyone mentioning that bark for 511 should be primarily between 1/16 and 1/8. Did you notice someone mention that or perhaps you are just thinking out loud.

    I think it will be difficult define the proportion. Proportion of different bark sizes varies from bag to bag. If you sift a bag of bark in to say three grades it will seem even more confusing. Let us you sift to three parts: less than 1/8, 1/8-1/4, and greater than 1/4. Then find the volumes of each and add those three numbers. You will notice it is larger than the volume you started with. When you mix them together the volume reduces since most of the smaller stuff will find the spaces between big stuff. In fact the space between the big stuff is quite a lot and so quite a bit of small stuff ends in the 511 mix.

    But if your bark happens to be very low in the finer material you can bump up the peat a bit a experiment with it.

    I usually pick up a handful of moist 511 mix and eyeball the look and feel and adjust accordingly. I also some bags of pine fines (less than 1/8) stored for adjusting if needed. These fines came from sifting bark for gritty mix.

  • Vance Evans

    Tropic I read it in the OP.

    " There will be a naturally occurring "perched water table" (PWT) in containers when soil particulate size is under about .125 (1/8) inch, so best would be particulates in the 1/16 - 3/16 size range with the 1/16-1/8 size range favored. "

    I'm thinking of trying 2 parts 1/8"-1/4" 2 parts 1/8"-1/16" in and 1 part 1/4"-1/2" as an experiment with 1 part perlite and 1 part peat.

    I'm thinking about purchasing a 1/12" sieve to make it more uniform.

  • PRO

    Ideal Particle Sizes

    In a perfect world, the mineral fraction for use in the gritty mix would range in size from 1/10 - 5/32" (.100 - .156", or 2.5 - 4.0mm). 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 3.25 - 6.25mm).

    For the 5:1:1 mix, particle size should be from dust to 3/8". (0 - .375", or 0 - 4mm), with most of the bark ranging in size from 3/16 - 3/8" ( .188 - .375", or 4.8 - 9.5mm). The perlite should be on the coarse side - something like the all purpose or super coarse shown below. If you read the size gradation next to the images, you'll see the images are misleading as the product appears to be much larger than the size listed in print.

    starter: 1/16 - 3/32 inch (1.6 - 2.4mm) you can sub #1 cherrystone/quartzite if available

    grower: 3/32 - 3/16 inch (2.4 - 4.8mm) you can sub #2 cherrystone/quartzite if available

    developer: 3/16 - 5/16 (4.8 - 8.0mm) you can sub #3 cherrystone/quartzite if available

    turkey: 5/16 - 7/16 inch (8.0 - 11.0mm)

    turkey finisher: 7/16 - 5/8 inch (11.0 - 16mm)

    The last 2 sizes of grit can be used as ballast in the bottom of shallow pots by mixing 3 parts of grit to 1 part of your soil; this, to avoid water perching above the layer. The layer should be as tall/deep as the PWT your soil supports. Skip this if using a properly made gritty mix.


  • edweather USDA 9a, HZ 9, Sunset 28

    Thanks for the clarification Al.

    @tropicofcancer, yes, 1/8 to 1/4 for gritty, as you and Al stated.

  • Vance Evans

    Thanks Al, guess it was a typo by the OP lol.

  • scapergirl (7a DE)

    Al, question for you if you’re around. Tropicofcancer has been helping me with my gardenia (long story short, heat stress and subsquent overwatering in a soil that started well drained and now 2 mths later has collapsed). I bought the ingredients for the 511 mix and am going to mix it up tomorrow after I sift the bark. I am just going to make enough to fill the 12” terracotta pot and considering it’s for a gardenia and my water is hard (7.5-8pH) should I add the dolomitic lime or leave it out to preserve the acidity that gardenias love. Thanks in advance, I have really learned alot from reading your posts throughout these forums for the past year.

  • PRO

    SG ...... I appreciate the kind words. You have a good mentor in ToC, which is invaluable when it comes to moving you forward along the journey to a green thumb.

    How I would treat gardenia and other plants that need a lower pH medium to thrive: A) Include the lime in the medium, but use a pH reducer when you water, Good choices are pH Down, citric acid, or white vinegar. You'll need a pH meter, and you should let your irrigation water set in an open container for 24 hours before you determine how much you'll need to bring the water pH down to 5.0-5.5. The pH will rise in that 24 hour period as the dissolved CO2 gasses off. B) You can leave the lime out entirely. If your fertilizer contains Ca and Mg you should be ok w/o it. If it doesn't contain one or both, use a teaspoon of prilled gypsum as a Ca source and Epsom salts as your Mg source. If you keep up on repots to avoid root congestion, you should only need to add gypsum when you make the medium. If you use Epsom salts, you could try adding 1/4 tsp to a gallon of water every time you fertilize. I cant provide you with the ideal amounts to use, because "ideal" would necessarily include what's already dissolved in your tap-water.


  • scapergirl (7a DE)

    Hi Al! Thanks so much for the reply! ToC has been an amazing help, great guy! So I made the mix today and did end up of adding the garden lime, because I am a rule follower. Can’t help it! LOL I barerooted the gardenia (sad how much fine roots were missing since the last bareroot in May ) But there are lots of thick white roots and some fine white roots forming too so I am pleased with that!. I pressed the 511 mix (pine bark sifited to 1/2” to dust; 5 parts, horticultural perlite sifted over insect screen to reduce dust; 2 parts, and peat moss (miracle grow); 1 part) into the root ball added soil to the bottom of the pot and a wick that extends through the hole and up to the rootball and lastly filled up the 12” pot to finish (rootball is only 1/2 depth of pot, is this too big now that the roots have reduced?). Next, I gave it just enough of a drink to have water run through the drainage hole. I usually use white vinegar to reduce my irrigation water to the 5pH range and add 1/8th tsp per gallon of foliage pro, since it contains all the nutrients, but I just used the garden hose for the inital watering in. Since I used garden lime in making the mix and use a weak solution of FP every time I water, do I need to do anything else this point forward? We are predecited to get storms tonight and tomorrow, should I bring it in the garage? Lastly, do I need to keep it in all shade for a while or can it get some sun during the day? Thanks again for your insight!!! I may be a landscape architect, but I have a really hard time with gardenias! LOL See photos below of my soil / roots:

  • tropicofcancer (6b SW-PA)

    Thanks scapergirl and Al for the kind words. I always learn something new when Al contributes. Or at least realize something new about stuff that I am not entirely sure about. I suggested scapergirl to skip the lime since she uses FP. And that she she has hard water- so probably enough Ca is coming in that way. But agreed one cannot really judge the contents of the tap water just from the Ph alone.

    I do add lime since I make the mix 511 in batches and store it ready to be used. They get plenty of time to settle in. And I have a variety of plants so I just to stick to one recipe. I do also use less than the recommended dose of lime though. Initially, after potting, I add MG shake n feed slow release pellets (does not have Ca/Mg) at half the rate. Through the summer I use FP every now and then. Between all that I think all the nutrients are covered. For the last few years we have been getting rain pretty frequently. The slow release fertilizer is my insurance against too much rain washing out nutrients and my laziness.

  • scapergirl (7a DE)

    ToC you’re welcome! I totallly understand why you suggested I skip the lime and in hindsight I should have used a tad bit less than the reccommended ratio, but that’s how we learn right!? My pH meter is reading at just about 7pH so I will take that over 7+ and will definately keep using the vinegar in my watering mix. I did not add the slowfeed granules, mainly because I forgot but I also like to be incontrol of the fertilzation more that it allows though I agree is does help with keeping the rainwater from washing out all of the neutrients!!! Now if we could only get some’s been over a week and every chance has amounted to not a single drop!

    Last question / observation: Would it be possible that I would need to water the gardenia every day? I moved it to the only bright shade all day location in the yard (which sadlly is about 3 ft from the AC compressor - though luckily when it runs it doesn’t produce very much wind) and it after doing a good flush in the AM by the time I went to bed it was 5 at the bottom of the pot on my moisture meter and 3.5ish in the rootball zone. Thanks again!!

  • scapergirl (7a DE)

    Decided the AC spot wasn’t the best decision, duh! I moved Monday morning it to a bright shaded spot and it has done wonderfully this past week. We had an amazing rain storm on Wednesday that allowed me to collect 2.5 gallons of H20 for watering this next week. Yea! I gave it a full dose of fert on Thursday morning after the rain.

    Today I moved it to a location that gets easterly sun from 10 am to 2pm. Is that too much much to start? It’s perfect weather here for the next few days, low 80s day and high 60s night!

    Last question, how dry should I let it get to encourage roots? I am showing top end of dry range (3) in root zone and low end of moist range (5) in bottom of pot. I am hoping to get leaves to sprout on the bare branches, but I don’t know if there is a way to do that other than just let it do its thing. Lots of leaf sprouts on tips of branches though!

  • tropicofcancer (6b SW-PA)

    Scpergirl: Did not notice this but I replied on the other thread.

    Summary: I water more often after a bare-root repot and not worry about root-rot for fresh 511. Also I hold off on the fertilizer for a week or so. But if your plant is not showing signs of stress keep doing whatever you are doing.

  • scapergirl (7a DE)

    Yes I did ToC! Thanks again!

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