Container Soils - Water Movement & Retention IX

tapla (mid-MI z5b-6a)July 20, 2009

I first posted this thread back in March of 05. Eight times, it has reached the maximum number of posts to a single thread (150), 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 again comes from the participants reinforcement of the idea that some of the information provided in good-spirited collective exchange will make some degree of difference in the level of satisfaction of many readers growing experience.

I'll provide links to the previous eight threads at the end of what I have written - in case you have interest in reviewing them. Thank you for taking the time to look into this subject - I hope that any/all who read it take at least something interesting and helpful from it. I know it's long, but I hope you find it worth the read.

Container Soils - Water Movement and Retention - A Discussion About Soilscolor>size>

As container gardeners, our first priority should be to insure 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. 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 IÂll 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 as an 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:

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 enough nutrients in available form to sustain plant systems. Gas Exchange - It must be sufficiently porous to allow air to move through the root system and by-product gasses to escape. Water - It must retain water enough in liquid and/or vapor form to sustain plants between waterings. 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 of water in 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, waterÂs bond to itself can be stronger than the bond to the object it might be in contact with; in this condition it forms a drop. 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 .125 (1/8) inch.. This is water that occupies a layer of soil that is always 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 perched. The smaller the size of the particles in a soil, the greater the height of the PWT. This water can be tightly held in heavy (comprised of small particles) soils and Âperch (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, and 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. 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: 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 drain better. 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?

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 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 starve/"suffocate" because there is insufficient air at the root zone to insure normal water/nutrient uptake and root function.

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 natureÂs 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.

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 havenÂt 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 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.

My Basic Soils

5 parts pine bark fines

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)

micro-nutrient powder, other continued source of micro-nutrients, or fertilizer with all nutrients - including minors

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)

1/2 cup micro-nutrient powder (or other source of the minors)

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)

micro-nutrient powder (or other source of the minors)

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 vigor closer to their genetic potential. 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, pea stone, coarse sand (see above - usually no smaller than ½ BB size in containers, please), Haydite, lava rock (pumice), Turface or Schultz soil conditioner, and others.

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

1 part uncomposted pine or fir bark

1 part Turface

1 part crushed granite

1 Tbsp gypsum per gallon of soil

CRF (if desired)

Source of micro-nutrients or use a fertilizer that contains all essentials

I use 1/8 -1/4 tsp Epsom salts per gallon of fertilizer solution when I fertilize (check your fertilizer - if it is soluble, it is probable it does not contain Ca or Mg.

Thank you for your interest.


If there is additional interest, please review previous contributions to this thread here:


Post VII

Post VI

Post V

Post IV

Post III

Post II

Post I

Some readers might also be interested in a discussion about fertilizer strategies for containerized plants at the link below.

Fertilizer Strategies for Containerized Plants

Thanks again, for your interest and for making this fun. ;o)


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Wow another new life for this thread! It's amazing that so much good information can be found in a single thread.

I'd like to thank Al for starting this thread four years ago and for all the great posts from GW members over the years! You all make this forum such a great place to share information. Virtually *anything* you'd want or need to know about growing plants in containers can be found somewhere within this 9-part thread.

Thanks again to Al for starting the thread, to GW for hosting the thread, and for the members who contributed so much info to the thread.



    Bookmark   July 20, 2009 at 8:18PM
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And, one more link. For those who need a refresher, are looking for something specific withing the threads and are unsure where to find it, or looking for common names of the items used, please see the link below.

    Bookmark   July 20, 2009 at 10:51PM
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kashu(z6 NJ)

Hello, my question is for Al and anyone experienced in rooting succulent cuttings in the gritty mix (turface/grit/bark).
I have been trying to root some jade cuttings in the gritty mix but have been unsuccessful so far. My cuttings are about 6" tall. I let the cut ends callus over and pot them in a clay pot with a mixture of equal parts aquatic plant soil, fir bark and rinsed, grower size gran-i-grit. They do not get watered and the humidity is not excessive. Within a few days of potting, the cut ends seem to get moldy. This has happened a few times already so I was wondering, is it not advisable to use rinsed grit when rooting? Could there be too much moisture in this mix for a callous jade stem. In the past, I have used slightly moistened potting soil to root and never had fungal issues. It seems to me that the moistened potting soil would have been wetter than the gritty mixture that I'm using now.

    Bookmark   July 21, 2009 at 3:10PM
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tapla (mid-MI z5b-6a)

I root many different succulents in the mix and have never had problems. Dipping the cut end in sulfur powder should stop the mold problem.

I would sever the cutting with a razor-sharp, sterile tool, dip in sulfur powder, leave it on the bench for a week or two, then pot into terra cotta, using dry gritty mix & wait another week before I started misting the soil ever so slightly. I've had jade (and many other succulents) that were on the bench for several months with cut ends that were not in soil (just hanging out in the air) that were putting out roots. Recently (May), I potted 6 cuttings of Aeonium arboreum atropurpureum 'Schwarzkopf' that were on my basement grow bench all winter. They were also growing roots in the air and struck quickly after potting them up.


    Bookmark   July 21, 2009 at 3:43PM
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shanielynn(9, Englewood FL)

Hate to jump in here but... kashu has had alot of success rooting jade and was just doing an experiment with a rinsed gritty mix. I pointed in this direction because the "Al mighty" has the answers. I know how you hate for others to send you in the direction of having to do their research for them but some of the other thread turned, ummm, really ugly for some reason??? I dunno.

I misunderstood things to begin with, got confused a bit but I am sure you have a better way of explaining things Al.

Again I hope this exchange helps at least a few people


    Bookmark   July 21, 2009 at 7:36PM
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kashu(z6 NJ)

I see, I have to use dry gritty mix initially, then gradually mist. Pretty simple, thanks Al.

    Bookmark   July 21, 2009 at 8:39PM
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tapla (mid-MI z5b-6a)

I went & read the other thread & see where it went south, but that happens frequently when you have a dozen folks with different ideas & they all would like to be right.

I didn't realize that Kashu had a fair amount of experience, so forgive the probably too specific advice. I think he has it right in his understanding that water isn't much of a priority for a good while when propagating this plant from cuttings.

I'll send you your finder's fee, Shannon - if you promise to drop the Almighty thing. It's embarrassing for me - I'm perfectly happy to be thought of as just one of the regulars. ;o)


    Bookmark   July 21, 2009 at 10:31PM
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shanielynn(9, Englewood FL)

Embarrassing! That's silly.

I think most of just want to offer some tried and true experience, not necessarily to be right but to offer some kind of explaination. (Or so I thought...)

Finder's fee: I think Kashu had already been around and prolly heard of you before... I'll take you up on that anyhow =D


    Bookmark   July 21, 2009 at 10:39PM
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shanielynn(9, Englewood FL)

Ok question... (may have been asked and answered, if so I apologize). When changing a planting over to 511, from say a store bought pepper plant, how much original soil should be removed? I could imagine trying to get some of that peat off would be hard on the plant???



    Bookmark   July 22, 2009 at 3:55PM
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tapla (mid-MI z5b-6a)

It's been asked, but I don't mind answering again. I don't expect people to sift through a million posts to find what they need, I do sort of expect people to take a hand in gathering their own information, though. E.g., if someone posts a question, the answer to which, is in the original text, I usually gladly answer it - especially if they are asking for some form of clarification; but if they start asking several questions that are clearly answered in the original text, I have to try to decide if they are really not willing to take part and want to be spoon fed, or if they might have a learning issue that makes it difficult to absorb what's been written. The ones that aren't willing to help themselves beyond only asking questions, usually end up with short shrift. ;o)

Your answer: It depends on the plant and the time of year. Ideally, almost all temperate plants would have all the soil removed during a spring repot, and tropicals the same, but the work would be done in the month before they exhibit their most robust period of growth.

Some plants just don't lend themselves to having all the soil removed, so for those plants, we do what experience tells us is reasonable. Hmmmm - as I think about it, most growers reading this wouldn't think removing soil from a plant's roots is in any way reasonable to begin with, so maybe that's not such a good gauge, eh? ;o)

You're going to be quite safe if you remove 1/2 of the soil at the first repot by cutting 2-3 pie shaped wedges out of the roots & leaving the rest of the roots/soil intact. Next spring, you can remove the older soil from the roots that remained last time. Surprisingly, plants recently repotted might sulk for a short time, but they almost always end up overtaking and passing, in mass, a counterpart that might not have been repotted by the end of summer or the growth cycle

It's not a good thing to have dissimilar soils in the same container. One soil will usually be too wet while the other is too dry.

Take good care GG. ;o)


    Bookmark   July 22, 2009 at 5:46PM
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shanielynn(9, Englewood FL)

Thanks! I did a search but the only way to the answers I was looking for in this and the previous 8 threads, was to google and cache... Memory is going to pot =D

I realize its not the best time to do so but they are having mood swings in their current conditions.

I need to repot several peppers into larger containers because I can not water 4 times a day (which they are now requiring). One of the plants was started with pepper seeds someone brought back from Mexico, so if I messed it up my DH would be pretty upset with me... tstl!! (to say the least) :D


    Bookmark   July 22, 2009 at 10:42PM
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Question about using lime vs. gypsum. Here's what I gather from reading various threads:

  1. If the potting mix is predominately peat and bark, add garden lime. For example, Al's 5:1:1 mix
  2. If the potting mix is NOT predominately peat and bark, add gypsum. For example, Al's Gritty mix.

Is this right? If not, what are the rules? Thanks.

    Bookmark   July 24, 2009 at 9:09AM
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tapla (mid-MI z5b-6a)

No rules - judgment call. Those soils with a predominance of conifer bark & peat will have a very low pre-liming pH and will benefit from the upward shift in pH that the dolomitic lime offers. It's a big plus that the lime contains Ca and Mg in a ratio favorable enough that it makes life easier.

Since the gritty mix has a higher starting pH it can't afford the boost in pH that the lime gives, so I elect to use CaSO4 (gypsum) and MgSO4 (Epsom salts) to supply Ca/Mg.


    Bookmark   July 24, 2009 at 9:42AM
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hi al,

iam sorry to hear about your bad misfortune the other day!!.

can you answer a question for me as best you can?, do
you think veggie,s can be grown in nothing but turface ?,
they would be grown in twenty five and thirty gallon
container,s fed at 1/4 or 1/2 strength f.p., what would
be your best guess as to watering cycle.s ? it is very
hot here, thank,s.

les matzek

    Bookmark   July 28, 2009 at 12:27PM
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tapla (mid-MI z5b-6a)

I'm sure they could be. It's an expensive way to go, though. If I was you, I would call around & see if I could locate a supplier that has it in bulk & buy it that way. Screening it to remove the fines will reduce it's water retention somewhat, too (it will hold LOTS of water).

There's no way for me to guess at how often you'd need to water. It depends on whether or not you screen, weather, how much plant mass is in the containers in relation to the volume of soil .....


    Bookmark   July 28, 2009 at 12:41PM
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i can buy fifty pound bag,s for 4.80 per bag i will see if
i can find a bulk supply.

how does turface hold water compaired to hydroton ?.
not postive veggie,s can grow in turface ?, thank,s al

les matzek

    Bookmark   July 28, 2009 at 1:13PM
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Turface will hold exponentially more water than hydroton. Hydroton is typically used for wicking in hydroponics, not so much water retention. To be clear it does hold a fair bit of water, but the larger size and less surface area result in it holding less than Turface.

Personally I would be afraid to use hydroton in an outdoor application as the watering frequency would likely be insane. Works fine indoors with houseplants though.

    Bookmark   July 28, 2009 at 1:22PM
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Paying less than $5.00 for a 50# bag of turface is a good price I believe. I don't recall seeing it for less than about $10 in my area.

I don't buy it often and there aren't many turface retailers in my area but I'd be happy paying $5.00 for 50#. I'm sure if you buy it by the pallet like Al probably does it's quite inexpensive as well.


    Bookmark   July 29, 2009 at 7:22AM
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hi al,
i have a heartland tomato plant in a 15 gallon container in
your 511 mix the plant is eight tall and ten inches wide it
has five open flowers on it, it seems to be growing very
slow i only have to water it every three days i do not
want to let it wilt unless you think i should ??.

the last two weeks here have been past 100 degrees do
you have any ideas why it is growing so slow ??.

the plant looks very healthy tho, regards.

les matzek

    Bookmark   July 30, 2009 at 1:15PM
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tapla (mid-MI z5b-6a)

This is primarily a discussion about soils, Les.

It could be the temperatures - any idea what the afternoon soil temps are? Can you shade the containers to keep the soil from heating up? You really don't WANT it to wilt, but I'm thinking you should hold on the watering and keep a close eye on it as you let it go to just barely the wilt stage at least once in the near future so you can gauge if you're over-watering.

When is the last time you fertilized - with what fertilizer - and at what strength (full, half ....)?


    Bookmark   July 30, 2009 at 2:18PM
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kevin_mcl(S Ireland)

I had some mixed Verbena plugs left over on the 15th of June and, out of curiosity, I planted them in three different types of potting soil. From left to right, soil based John Innes No2. - a standard peat-based compost and Al's 5-1-1 mix.
The Verbena in the 5-1-1 mix consistently seemed to have denser bushier growth. Weather has been extremely wet here throughout July.

    Bookmark   August 1, 2009 at 10:21AM
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Hello Al,

I am a newbie gardener and you would cringe at the state of my containers (I'm currently using a mix of garden soil from the backyard and compost, not even a peat based mix from a box store). I have alright results (plants grew and bloomed), but for the ammount of effort I put into them, I expect better returns!

I'm so glad I stumbled upon your thread. I'm already gathering supplies for next year (you guessed it, new soil mixes). The big box stores were no help to me. I'm fortunate to live 6.5 miles from a turface dealer (she actually asked how many tons I wanted). So I ordered 100 pounds of MVP. I was able to find pine bark mulch (4 cubic feet), but I'm not happy with the coarseness of the product. I'll have to screen it somehow to get rid of the big stuff or keep looking for better fines elsewhere. A trip to the local feed and seed store found granite grits (coarse, 100 pounds).

The feed and seed store also sells perlite in 4 cubic foot bales. The box stores all sell sphagnum peat moss in 2.2 cubic foot bales. I'll get a CRF and mirco nutrient mix next year closer to the growing season (from what little I understand, fertilizer doesn't store well)

Other than quality pine fines, I believe I've found everything needed to make your 5-1-1 and gritty mixes. I plan on experimenting with an all turface mix, gritty mix, 5-1-1, and some kind of peat based mix.

I just wanted to thank you for sharing your knowledge with us beginners.


    Bookmark   August 11, 2009 at 4:45PM
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tapla (mid-MI z5b-6a)

You're very welcome, Mike. IO enjoy the feeling that I might be helping, and look at my time here as a natural extension of my passion for growing things.

A few offerings:

* For the pine bark - look for a product where (practically) all pieces are smaller than a dime. Partially composted for the 5:1:1 mix is better, and uncomposted 1/8-1/4 pieces are best for the gritty mix

* Gran-I-Grit in grower size, or #2 cherrystone is best for the gritty mix

* If you use a 3:1:2 ratio (do you understand ratio vs %s?)soluble fertilizer like MG, Peter's, or Foliage-Pro, you won't need the micro-nutrients, but be sure you lime the 5:1:1 mix and add gypsum to the gritty mix & then add Epsom salts when you fertilize (read up on it above or in the other threads, or ask)

* Fertilizer stores fine. You just need to try to keep moist air away from the small open bags of granular soluble fertilizers like MG and Peter's.


    Bookmark   August 11, 2009 at 4:58PM
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I just checked the bag of Gran-I-Grit and found that #2 is indeed the "grower" size. I saved my receipt and well exchange the #3 for the #2. Out of curiosity (because I assume you have already tried), how big of difference would using the #3 instead of the #2 make?

The pine mulch I bought is going to be just that, mulch. I'll keep looking for fines (I have all winter). Perhaps the seed and feed store sells fine pine as bedding or something. Just the excuse I needed to look around the store a little more :).

I have a 50 pound bag of garden lime (from a previous project), but its a fine powder. Will that work or should I look for the coarse stuff?

I've seen bags of gypsum at the box stores, I'll be sure to pick some up along with the CRF (Any particular flavor I should look for?).

The water soluble fertilizer (Schultz) is 24% 8% 16% which is a 3:1:2 ratio if I remember my math correctly. It saids "with mirconutrients". I think I have Epsom salt somewhere.



    Bookmark   August 11, 2009 at 6:56PM
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tapla (mid-MI z5b-6a)

How much difference the larger particle size makes depends on the size of the other ingredients. If the Turface and bark are the same size (1/8" +/- a small fraction) it wouldn't make near as much difference as if one of the other ingredients was also too large. Ideal, is all particles at very near 1/8", or just slightly under.

For the 5:1:1 mix, look for soil conditioner, aged pine bark, or other products labeled 'pine bark'. If you can find Fafard's aged pine bark, it will work well, but you may need to increase the perlite's presence as I've found it a little to water retentive for my taste, but then I generally grow in mixes even more coarse than I describe here.

The powder, if it is labeled 'dolomitic lime' is likely the same as the prilled (pelletized) version, except that it hasn't been prilled. Look to see that there is 2-4x as much Ca as Mg, and you'll be fine. If there isn't, I would look to another product - to make things easier on yourself.

Make sure you get the lime/gypsum/Epsom salts thing clear in your mind before you move forward.


    Bookmark   August 11, 2009 at 7:13PM
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I e-mailed Fafard to find a retailer close to me. I forsee a possible road trip in my future.

I think I'll just buy new dolomitic lime to be safe (and use the other stuff on the lawn).

I think I have the start of a grasp on the lime/gypsum/Epsom salt thing. I'll have to do further reading of course :). Here goes.

The dolomitic lime, which is CaMg(CO3)2, is used in the 5:1:1 mix to supply Ca and Mg (at 2-4x more Ca than Mg), and to raise the pH (because the peat moss lowers it, and the lower the pH, the tighter P is held).

The gypsum, which is CaSO4*2H2O, is used in the gritty mix to supply Ca.

Epsom salt, which is MgSO4*7H2O, is used to supply Mg to the gritty mix because most water soluble fertilizers don't contain Mg or Ca (I checked mine, and it doesn't). The Epsom salt is added at the rate of 1/8 to 1/4 tsp per gallon of fertilizer (which is 3/4 to 1 tsp of fertilizer per gallon of water)

Water with a weak solution of 3:1:2 fertilizer every watering because plants absorb it better at low concentrations. When watering, 10 to 15% of the water applied should pass through the drain hole to "flush" salts from the soil.


    Bookmark   August 11, 2009 at 9:54PM
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tapla (mid-MI z5b-6a)

Sweeeeet! ;o)


    Bookmark   August 11, 2009 at 10:31PM
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Hey sounds like you have a great handle on both the 5-1-1 and gritty mixes! It took me a long time to find all the ingredients and figure out the fertilizer side of things, but once you do some reading of this thread and the previous eight threads it does make sense. Al was most generous with his time, both on and off-list, and answered many of my "newbie" questions.

I'm sure your plants should respond much better using these soil mixes next season. My trees are showing huge root growth this season in the gritty mix.

Granted, hunting down the ingredients, sifting fines, and mixing the soil it is a bit more work than just buying a bag of MG potting soil, but I have no doubt that in general plants grow better in the 5-1-1 and grit mixes with proper fertilization, watering, drainage and air movemnet through the root zone. The peat in the MG soil acts like a sponge and retains far too much water for far too long, preventing air from getting to the roots and keeping the roots soggy.

I agree that typically the big box stores are not very helpful when it comes to finding the right ingredients for the soil mixes. Granted, a few list members have found the right size of pine bark, turface or even silica sand at a HD or Wal-Mart but typically in my area you have to go to local hardware stores, feed stores, etc. to find the ingredients. In my experience, if you go to HD or Lowe's and ask for turface no one has any idea what you are talking about. Sounds like you've already found some great sources for your materials!

Good luck next season and be sure to keep us posted on how your plants do in the new mixes.



    Bookmark   August 12, 2009 at 7:19AM
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hi al,
is turface more closer in size then floor dry (8822)?.

thanks ,

les matzek

    Bookmark   August 12, 2009 at 11:57PM
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tapla (mid-MI z5b-6a)

In the size dept, there is a little variation from bag to bag for both products, but floor-dry seems to get a slight nod for having a higher % of usable pieces after screening for the gritty mix. No screening necessary if you use it in the 5:1:1 soil.


    Bookmark   August 13, 2009 at 10:08AM
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BTW, just wanted to give and update on my trees growing in the gritty mix. I just watered them yesterday and nearly every tree, regardless of container size or shape, now has roots growing through the drainage holes. Obviously there's some massive root growth taking place!

The concolor fir trees are the largest and oldest trees, and they have roots as long as 3 or 4 inches sticking out of the containers, and they were heavily root pruned this past April.

Even the tiny 2nd season white spruce seedlings have roots sticking out of their containers (actually aquatic plant baskets).

Remarkable growth for sure, probably due to the great gritty mix soil and the the regular feedings and waterings. In addition, the trees get direct morning and early afternoon sunlight, but late afternoon shade, which helps protect them from the very hot afternoon sun.

I have no doubt the gritty soil and watering/fertilizing schedule made most of this dramatic root growth possible.

Thanks Al, JAG and everyone who answered my *many* questions.


    Bookmark   August 14, 2009 at 7:35AM
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rj_hythloday(8A VA)

''In the size dept, there is a little variation from bag to bag for both products, but floor-dry seems to get a slight nod for having a higher % of usable pieces after screening for the gritty mix. No screening necessary if you use it in the 5:1:1 soil

Al, I screened my floordry #8822 and came away w/ about a quart of fine powder/dust size particles. Wouldn't that clog up the 5-1-1?

Are you saying there's no need to screen the floordry? I thought you didn't screen turface?

    Bookmark   August 17, 2009 at 10:53AM
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tapla (mid-MI z5b-6a)

There's not enough fine material in the floor dry to clog up the 5:1:1 mix because the fines are a small fraction of a small fraction of the soil. IOW, the floor dry would probably replace the perlite or be somewhere near 15% of the mix, with the fine portion being a small fraction of that 15% - so it won't matter. If you want - go ahead & screen it. I just offer guidelines anyway. I sort of expect you guys to want to familiarize yourself with how the soil components work together to the degree you can soon make appropriate decisions about how to go about mixing them. ;o)

If I was using Turface in the 5:1:1 mix, I wouldn't screen it, but I always screen it for the gritty mix. Of course, that's not carved in stone either, it's just what I've found to suit my own purposes/needs best.


    Bookmark   August 17, 2009 at 11:08AM
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How well does sphagnum moss substitute for peat?

    Bookmark   August 17, 2009 at 1:14PM
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tapla (mid-MI z5b-6a)

If you don't mind the expense, it should substitute for peat very favorably. It's great stuff - excellent water retention properties, and unlike sphagnum peat, in its live form it is able to retain its open structure and so drains quickly and remains well-aerated for a full grow season.

Less well known is the fact that sphagnum moss has a high zinc content in the form of a naturally occurring antibiotic called Tropolene. The anaerobic bacteria that cause decay in wood are (at least partially) nullified by the antiseptic properties of sphagnum moss. Hence, pure sphagnum (without the addition of any other organic material) is an ideal medium for re-invigorating weak plants, and plants with root-rot.


    Bookmark   August 17, 2009 at 2:35PM
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