5 years ago
last modified: 5 years ago

Hello! Houzz's new format has presented some challenges, but it
looks like there has been some changes that will allow me to repost the thread
in its entirety. Hopefully you'll view that as a GOOD thing. I need to
thank all the growers and good people who have been so supportive of the thread
over the years. Their contributions are one of the main reasons viewers
continue to find interest in it, so thank you very much! If you find value
in the information I have set down in this post and feel there is anything
pertaining to the topic that should be added or explored in more detail, please
contribute your suggestions. My goal was to offer soil-related information with
the potential to help you increase the reward you get in return for your
efforts. What might I do to increase the value of this offering?

As you eye the length of this post, one thing you might ask
yourself is, "Why the interest and all this talk about soils and water
retention?" In all honesty, soils obscure the reason we talk about them -
they hide the roots and the roots' state of vitality. Vitality is not the same
as vigor. Vigor is a genetic factor, something the plant is endowed with because
of how it was programmed by Mother Nature.
It is also something we have no sway over. Vitality, on the other hand,
is dynamic and variable, essentially a measure of how well a plant is/ has been
able to deal with the cultural hand it has been dealt. Vitality is something
you have much control over. It is the visual signals we get from the parts of
the plant we CAN see that allow us to take measure of the condition of the
roots, their vitality. Soil choice, combined with watering habits, have a very
significant impact on root health. As you read, keep in mind that good root
health and root function is an essential PREREQUISITE to a healthy plant.
You cannot expect to grow healthy plants w/o a healthy root system - it is
impossible; which brings us full circle to why we discuss soils.

Poor root health is responsible for a very high percentage of the
ills that befall plants, and the reasons people flock to the forums seeking
help for widely varying issues. Poor root health means a reduction in vitality,
which leaves the plant looking shabby while compromising its ability to defend
itself against insects and diseases.

So let us talk about some things we can implement that should go a
very long way toward providing you with the ability to consistently keep the
root systems of your plants happy.

I started this
thread about 10 years ago, in March of '05. So far, it has reached the maximum
number of posts GW allows to a single thread twenty times, which is much more
attention than I ever imagined it would garner. I have reposted it in no small
part because it has been great fun, and a wonderful catalyst in the forging of
new friendships and in increasing my list of acquaintances with similar growing
interests. The forum and email exchanges that stem so often from the subject
are in themselves enough to make me hope the subject continues to pique
interest, and the exchanges provide helpful information. Most of the motivation
for posting this thread another time comes from the reinforcement of hundreds
of participants over the years that strongly suggests the information provided
in good-spirited collective exchange has made a significant difference in the
quality of their growing experience. I'll provide links to some of the more
recent of the previous dozen threads and more than 3,000 posts at the end of
what I have written - just in case you have interest in reviewing them. Thank
you for taking the time to examine this topic - I hope that any/all who read it
take at least something interesting and helpful from it. I know it's long, and
grows a little longer each time it's reposted. My hope is that you find it
worth the read, and the time you invest results in a significantly improved
growing experience. Since there are many questions about soils appropriate for
use in containers, I'll post basic mix recipes later, in case any would like to
try the soil. It will follow the information.

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


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

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

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

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

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

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

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

ROOT HEALTH/ FUNCTION/ METABOLISM. If you ask yourself, "Can I water
correctly if I use this soil?" and the answer is 'NO' .... it's not a good
soil .... for the reasons stated above.

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

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

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

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

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

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

Food for thought:

'A 2-bit plant in a $10 soil has a future full of potential, where
a $10 plant in a 2-bit soil has only a future filled with limitations.' ~


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

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


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

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

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

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

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

Continued below

Comments (1K)

  • Bill
    5 years ago

    Hi Al,

    I am new here. I have read 20 previous
    threads about water movement in containers. I want to thank you.
    Because of all of your hard work I am getting good results with my
    potted plants now.

    I want to give something back. 3/8 inch
    hardware cloth is really hard to find. ½ inch is easy to find.

    I made a 3/8 inch screen using ½ inch
    hardware cloth. It works very well. It has two layers of ½ inch
    screen offset so that the largest squares are 3/8 inch.

    After the first layer is attached to
    the frame the second layer is aligned by putting 3/8 inch rods
    through holes in both layers then snugging up the second layer so
    that it is tight to the rods. Fasten the second layer. Remove the
    rods, 3/8 inch bolts might be easier to find then rods and could
    be used the same way.

    To finish the screen it is necessary to
    fasten the two layers together at several points so that larger
    pieces cannot work there way through the two layers one at a time. I
    did this by fastening two narrow strips of wood across the outside
    bottom of the screen Then from the inside using six roofing nails I
    nailed the two layers together. The wood strips are one inch wide.

    Thanks again


    tapla thanked Bill
    Best Answer
  • tropicofcancer (6b SW-PA)
    9 months ago

    Cool, so there is another book out by Jerry. I have the first one signed by him.

    tapla thanked tropicofcancer (6b SW-PA)
  • Sergey Varlamov
    9 months ago

    Al - Can this daily fertigation be generalized for all (or mostly all?) container plants in well-draining soils?


    tapla thanked Sergey Varlamov
  • tapla
    Original Author
    9 months ago

    The medium would need to be even less water-retentive than the standard 1:1:1 gritty mix, and screening all ingredients to an appropriate size would be a necessity.

    During winter when all my tropical/subtropical trees (about 100) are indoors, I fertigate with a weak fertilizer solution every time I water, which is about every 5-6 days for larger pots and every 3 days for a few plants in extra small pots. Keep in mind that my plants are almost all in very small bonsai pots, which significantly shortens the appropriate interval between waterings.


  • JodiK
    8 months ago

    And years later, here I am, still having great success using the basic concepts contained within your original article! :-)

    tapla thanked JodiK
  • bragu_DSM 5
    7 months ago


    tapla thanked bragu_DSM 5
  • mblan13
    6 months ago

    1000. WooHoo!

    tapla thanked mblan13
  • tapla
    Original Author
    6 months ago



  • Gregório Miranda
    5 months ago
    last modified: 5 months ago

    Guys, I can't find turface or pumice where I live (Brazil). Do you think grounded terracotta (crushed bricks) could be a reasonable substitute? It's (very) frequently used as a soil ingredient for bonsai.

    tapla thanked Gregório Miranda
  • tropicofcancer (6b SW-PA)
    5 months ago

    That looks like an excellent replacement for turface. Crushed brick usually will tend to have sharp edges. Yours look more rounded. Are you sure it is crushed brick. In India, crushed terracotta and bricks is often used as a container soil component, especially bonsai. But it looks different that your picture.

    tapla thanked tropicofcancer (6b SW-PA)
  • Gregório Miranda
    5 months ago

    Good to know! I'll plant succulents with it, should I add perlite for more water retention? About the picture, it's not mine actually, so I can't say. I just took one from google for exemplification.

    tapla thanked Gregório Miranda
  • tropicofcancer (6b SW-PA)
    5 months ago

    Crushed brick/turface will, in general, have more water retention than perlite. Perlite holds water on the surface and is not internally porous. So depending on the kind of succulents it may be a good thing to use some perlite to reduce water retention of pure turface. The particle size would need to be in a similar range as turface (1/8-1/4). Also crushed brick or terracotta are not exactly the same with regards to water retention. Some may be more water retentive than others - some may be more dense and others may be more porous depending on material used and firing temperatures. You have a hotter climate in your region and may be even more rainy so you will have to experiment a bit to get it right.

    tapla thanked tropicofcancer (6b SW-PA)
  • mblan13
    5 months ago
    last modified: 5 months ago

    Al, It was the 1000th comment. I saw the comments were at 999. Couldn't resist!

    tapla thanked mblan13
  • mblan13
    5 months ago

    Gregorio, I use a product called Optisorb in place of Turface. It is a Diatomaceous Earth (not the powdered kind) and used in factories for absorbing spills. You might be able to find a similar product in your area. Just make sure its 100 DE, and it would be a good idea to do a test soak in water first.

    tapla thanked mblan13
  • tapla
    Original Author
    5 months ago

    I wondered if that's what you meant. This thread subject has been active since 2005. Garden Web policy was to terminate the ability to post to a thread when it reached 150 posts. That happened 21 times, so before this thread, there were 21 reposts with 150 replies each. With this thread having about 1,000 contributions, altogether, since its initial posting, there have been roughly 4,200 contributions. How time flies ......... which reminds me of a joke: Time flies like an arrow; fruit flies like a banana.

    The idea for this thread came to me because of the painfully slow process I had to go through to get to where I could count on being able to keep almost anything I grew in a high state of vitality. I hoped putting (nearly) all of the basic information about the physical properties of container media in one place and making it understandable, would significantly reduce the length of time it might take to gather the knowledge in piecemeal fashion. Lately, I haven't been as active on the thread as I have been in the past, in large part because so many growers (who participate here) have gained a very good working knowledge of the topic and are willing to help share their thoughts and experience(s). I think now would be a good time to thank everyone for both their questions and answers, challenges and contributions, and for the time it takes to help your gardening counterparts. I DO appreciate what everyone has and will share with others as additional questions arise.


  • Gregório Miranda
    5 months ago
    last modified: 5 months ago

    Ah, nice, recently I found a cat litter made of diatomite. Didn't get it yet, but will definitely give it a try.

    tapla thanked Gregório Miranda
  • tropicofcancer (6b SW-PA)
    5 months ago

    I have tried cat litter once and there are others that have used it. Make sure it is fragrance free and that it does not turn into mush. A good way to test if it is usable is to saturate it with water try to crush it with your fingers. Then freeze the stuff and thaw it and repeat the crush test. If it is not easy to crush it then it is usable as a soil component.

    tapla thanked tropicofcancer (6b SW-PA)
  • Gregório Miranda
    5 months ago

    Nice, I'll do it, thanks!

  • JodiK
    5 months ago

    Al, you can't imagine what a positive impact this thread has made, for my ability to grow containerized plants that are healthy and happy! The concepts presented are absolutely sound, easy to understand, and easy to make any small changes necessary to the individual environment or micro-environment.

    I continue to share this thread and the information contained herein, helping others to understand the part roots, mediums, and basic physics play in growing potted plants optimally!

    I can't thank you enough for sharing your knowledge! It's made me a better gardener, both with potted plants and those I grow outdoors in raised beds or other garden areas.

    Fir bark, coarse perlite, and granite chips still make up the basics of what I use, but it's actually the concepts that have helped me to tailor mediums to my individual plants and their needs.

    There are many other ingredients that can be substituted, given what is available within one's area. I would think crushed bricks, when sifted to obtain the right size, would be a decent substitute, and they would help to retain a bit of moisture. I would use it if that's what were available to me.

  • Gregório Miranda
    5 months ago
    last modified: 5 months ago

    I too indeed can confirm that reading this topic and others from Al are helping greatly! I'm reading a lot about gardening lately, but I've never found quality information like this.

    AND, I have another practical question:

    If I mix Dolomitic lime (Ca + Mg) and Gypsum (Ca + SO4) at a 1:1 ratio, would it be a suitable source for all the secondary nutrients (Calcium, Magnesium and Sulfur)?

    Ps.: The Dolomitic lime I got have a ratio of Ca to Mg approximately of 1.5:1. Not very good, I suppose, but maybe adding gypsum could correct this.

  • Just Started(Sydney)
    5 months ago

    Gregório Miranda next step is to master the art of root pruning. Good old Al has a thread for that too.

  • Sergey Varlamov
    5 months ago

    Hi - Would appreciate a link to root pruning thread please!

  • tapla
    Original Author
    5 months ago

    I wasn't fishing for a compliment, but I do appreciate the very kind words. Thank you.

    AND, I have another practical question:

    If I mix Dolomitic lime (Ca + Mg) and Gypsum (Ca + SO4) at a 1:1 ratio, would it be a suitable source for all the secondary nutrients (Calcium, Magnesium and Sulfur)? Media pH, irrigation water alkalinity, and composition of your supplemental fertilizer should be your guide insofar as what you choose as a liming agent, or if you use one; and, if you use either CaSO4 or MgSO4, S availability shouldn't be a problem. For most container plantings (but not all), you'll want Ca:Mg ratios in the soil solution somewhere around 3-5 Ca : 1 Mg.


  • JodiK
    5 months ago

    I know you weren't fishing, Al... but you deserve accolades, anyway. :-)

    I've said it before, but the gardening industry is like any other... it lives for profit. Turnover creates profit. If people were told what they really needed to know, instead of a bunch of fallacies and old wive's tales, that profit wouldn't be nearly so grand.

    And while there are plenty of books available, a lot of them are written in jargon the layman doesn't necessarily understand. That, or they continue to preach the same old non-wisdom where growing in confined spaces, commonly known as pots, are concerned.

    Rarely is it written that growing in pots differs greatly from growing directly in the ground... where Mother Nature's army of worms, nematodes, fungi, and other critters and natural processes do all the work necessary to aerate and to break down decaying matter into usable food ready for uptake by a plant's roots. It's next to impossible to recreate this natural process using potting soil and certain commercially sold fertilizers in a container environment.

    But Al has effectively given us the information needed, and in terms we can all grasp, so we don't have to keep replacing plants, or grow them in what are less than ideal conditions which cause them to give us less than ideal growth and blooms.

    Again... there's no such thing as a "green thumb"; it's nothing more than applied knowledge.

    Happy Growing!

  • mblan13
    4 months ago


  • Dylan
    4 months ago

    Thank you Al and Rob for the incredible advice.

    After reading through (most of) the comments in this thread so far, I still have a couple of questions.

    Can Rice Hulls be a substitute for Pine bark. I have access to both, but I've just come across a wonderful shop that stocks the majority of materials discussed, and they stock rice hulls. Meaning less work screening Pine bark chips.

    The other question I have is not about the gritty mix. Just the plain mix for indoor plants.

    Is it detrimental that the Perlite be of coarse type? Again, I can access both normal and coarse, but regarding all of this, I'm trying to work out how important it really is.

    Because one product might mean me driving for 2 hours to get as opposed to driving 15 mins.

    tapla thanked Dylan
  • tapla
    Original Author
    4 months ago
    last modified: 4 months ago

    Pine bark has a greater % of lignin (makes plants hard and woody) and a smaller fraction of cellulose than rice hulls. Pine bark is also very rich in suberin, a lipid that might be referred to as Mother Nature's waterproofing for plants. Together, these factors mean that media made with a large fraction of rice hulls, already a fairly fine material, will break down much faster than media based on a large fraction of pine bark.

    I've purchased plants in media with rice hulls or crushed peanut shells, and at repot time wasn't impressed with their structural state. Because of that fact and even though they are readily available to me, I've never considered using them in any of the media I make, even though I know they are commonly used for those whose interest in how the media performs is limited to the short period between potting up plugs and moving the finished product to their POS.

    When it comes to perlite grades, I prefer propagation grade coarse, and that's all I buy. For the 5:1:1 mix or other media based on a large fraction of pine bark in the dust to 3/8 size range, one grade finer (medium/soil mix grade) perlite works about as well as the propagation/coarse grade. Reason - even a small particle of perlite wedged between flat bark chips is capable of creating a large pore space.



  • Dylan
    4 months ago
    last modified: 4 months ago

    Thanks Al

    Appologies if you've mentioned any of this already, but I'm still crawling through 8 years worth of information! And time is of the essence as I have a very sick plant. (I promise you I'm reading it all though!)

    Why do you use pine bark as a medium? I know you said that it takes a long time to break down and it's large enough to aerate the soil. But why couldn't you just use a rock that isn't porous? Wouldn't that be the same thing but with the added benefit of not breaking down? And why do you not mention the use of Vermiculite as a substitute for Turface anywhere? Is it because of the size? And do you ever alter the drainage holes that come in your typical house pot by adding more or increasing the size of the hole?

    The perlite I've been buying is fairly small. About the size of a BB or the size of a ball bearing. They're quite small and brittle.

    But i can get the coarse stuff we're talking about so that's all fine.

    tapla thanked Dylan
  • tropicofcancer (6b SW-PA)
    4 months ago

    But why couldn't you just use a rock that isn't porous?

    Yes you could and that is what gritty mix has in considerable proportion. Gritty is composed of granite chips (chicken grit growers size), turface and pine bark. But that makes it heavy and more expensive too. For many it is not easy to source, sift all the material. You could even make mixes without any bark at all. Many in the bonsai world do that. Lava rock, pumice, turface (or their equivalent such as akadama), grit are popular soil components in bonsai. 511 is not as durable as mixes with more fractions of grit, turface etc but it is cheap to make, very lightweight and still provides the needed moisture retention and aeration.

    And why do you not mention the use of Vermiculite as a substitute for Turface anywhere?

    Vermiculite is small, retains way too much water and degrades fast and becomes mush. It is not a good component of soil mixes except may be in seed germination mixes.

    The perlite I've been buying is fairly small. About the size of a BB or
    the size of a ball bearing. They're quite small and brittle.

    You should get the coarser variety if you can. But BB size should work too. They are brittle by nature. May also have a lot of dust that needs to be sifted out using an insect screen. Wear a mask and do the sifting outdoors. Those fine dust are not good for your lungs.

    tapla thanked tropicofcancer (6b SW-PA)
  • tapla
    Original Author
    4 months ago

    Dylan - remember in our off-forum messaging, my saying there will be others who will answer questions here, and I would disagree if I thought the info was wrong or needed clarification? ToC's reply is what I was referring to. Nothing to disagree with, so I normally wouldn't even comment. The essence of what he said is exactly the message I'd've offered.

    I did think of one thing as I was closing, re using nearly all inorganic material for your medium, that might be useful. The gritty mix uses two inorganic components, one is internally porous and holds lots of water (Turface/calcined clay), the other (crushed granite or cherrystone/quartzite) is not internally porous and holds water only on the surface of particles (and at the interface where particles touch each other in the medium). This affords you the option of adjusting water retention by way of varying the ratio of the two inorganic products. Illustrated:

    basic recipe:

    1 part screened pine or fir bark

    1 part screened Turface

    1 part screened/crushed granite or cherrystone (quartzite)


    more water retention:

    4 Turface

    3 bark

    2 granite


    less water retention

    4 granite

    3 bark

    2 Turface

    All the above are by volume.


  • Dylan
    4 months ago

    Is there a known substitute for Turface?
    There’s really only one supplier here in Aus that sell that stuff, so I’m sure the day will come when it’s unavailable when I’m going to need it...

    tapla thanked Dylan
  • tropicofcancer (6b SW-PA)
    4 months ago
    last modified: 4 months ago

    You can look for diatomaceous earth or DE for short. Here in US it is available in Auto Shops (NAPA 8822 I think) and is used to absorb oil spills. Kitty litter may also have DE or turface like clay. But you have to make sure they are durable. Some brands may have too soft a substance that will degrade over time. A good test is to soak them and then go through freeze thaw cycle three times. If they do not break between your fingers then it can be used.

    Turface may have other names in your area. It is used in baseball fields. That is its primary purpose. So look into those suppliers. In US commercial landscape suppliers carry them under various brands.

    Try bonsai clubs and forums in australia. They may have a better idea. Eg: ausbonsai.com.au/

    tapla thanked tropicofcancer (6b SW-PA)
  • tapla
    Original Author
    3 months ago
    last modified: 3 months ago

    Turface is calcined clay. 'Calcined', means it's baked at high temperature so it's nearly ceramicized. DE can also be calcined. In addition to the freeze test ToC mentioned, you should also be sure (if you're considering a kitty litter product) that it contains no perfumes or clumping agents - especially bentonite, which is another form of extremely fine clay that would be disastrous used in a medium, as it turns to a pudding-like consistency when moist.


  • Dylan
    3 months ago

    Is the point of Turface to retain water but also that it's size is adequate for proper drainage? Crushed brick is quite easy to get here - and it's sustainable / cheap

  • tapla
    Original Author
    3 months ago

    Crushed brick (Haydite, in the US) is somewhere between crushed granite and Turface in it's ability to hold water, closer to crushed granite than Turface. I sometimes add a small fraction of it to the gritty mix basic 1:1:1 recipe I keep on hand, already mixed, to reduce water retention for some plants - mostly pines and junipers.


  • tropicofcancer (6b SW-PA)
    3 months ago

    Al: Isn't Haydite just expanded shale? Or is the term used for crushed bricks too? I agree it would have properties between granite and turface.

    Crushed brick can wide range of properties depending on how it is made. Bricks can be made from both clay and concrete. Clay would have better properties from a plant perspective. But its porosity will depend upon how compressed it is. Fire clay bricks, for example, is very very dense. They will be close to granite. In fact, the density is pretty close. Regular clay bricks can range from porous to not-so porous. In India, where turface is not available (no baseball there or not much of golf either - the two places where turface is primarily used) crushed brick is popular component for bonsai soil mix. Biggest trouble is sifting to get the right size range. In India, crushed brick sources will have dust to more than an inch chunks in there. That is because it is sold as fill material rather a soil component. Pain to sift and usable portion can be quite small fraction of the whole.

    tapla thanked tropicofcancer (6b SW-PA)
  • tapla
    Original Author
    3 months ago

    If you have interest, the link will explain why it's often (and still) referred to as crushed brick. It can also be made of either clay or shale. The product I have is already screened from about 1/16" - 3/16" (1.6 - 4.7mm).

    Porosity varies in the US too, where it is used primarily for making lightweight concrete. We even made barges from it that are used on The Great Lakes and the Mississippi River.



  • Sergey Varlamov
    3 months ago

    To Dylan - You are in Oz, right? Me too. I have not been able to find turface anywhere at all but there are some substitutes. The best is Seramis, calcined clay specifically made as grow media:

    https://www.luwasa.com.au/seramis. But expensive: I buy a box of 10 2L bags for AUD130. So, I don't use it alone but anything between 1/2 to 1/4 with the rest are pumice, (or zeolite, or DE) and pine bark fines. Also you can find pumice, zeolite and DE, as well as pre-mixed "gritty" soil, here: https://www.drgreenthumbs.com.au/collections/cactus-bonsai-succulent-grow-mediums-australia?page=1.


  • Dylan
    3 months ago
    last modified: 3 months ago

    Hi Sergey,

    I've found Turface. I'm actually picking up some tomorrow.

    You can buy it from Sage Horticulture


    He's the only guy I know of that stocks it here and he gets it from a supplier in QLD. But I believe he ships it also. I can find out for you tomorrow.

    Everything else is easily accessible for me. All of it, Bunnings stock. I'm supplementing the crushed granite for some pebbles or quartz of the same size.

    The Bark chips are available nearly everywhere here, though I'm trying to find them small enough that I can sift them without having to spend a lot of time doing so. I've found some Reptile bark which isn't any bigger than about 10mm in size - which is kind of perfect as a starting point, but it's about $20 for a 9L bag, so it's more expensive than buying the big size bark from Bunnings. But it would be much less time consuming.

    I'm also trying to work out a way to mulch up the remaining big pieces of bark if I buy a bag of the big stuff so none goes to waste. I need a minimum of 40L of bark!

    I think I might buy a cheap blender from Target that can cut them down in small batches and then sift them - so I can get more out of a bag. The local plant nursery also sells pine fines - which I'm going to buy a bag of and see if it would be easier to sift.

    I'm also contemplating buying a bag of Euci-Mulch (which is Eucalyptus tree bark or the inner tree - i'm not sure) as an experiment for one or two plants.

    Bunnings sell this also. It looked like a very nice consistency once it's sifted but I'm not sure how it will react with any plants or if there are any drawbacks. Only one way to find out I suppose. It's quite cheap.

  • Dylan
    3 months ago

    Does anyone know if I can use a pine bark with a water wetting agent added to it?

  • tropicofcancer (6b SW-PA)
    3 months ago

    Al that article is very informative and enjoyable read. Now I know the origins of Haydite. I knew that it is used as concrete aggregate.

    Also wanted to clarify that I did not mean to convey that bricks in India are something special. They are the same/similar to what is available here in US. Just that in India it is often used as a soil component because of lack of other materials.

    Dylan, commercially wetting agents (basically surfactants) are used in soil. Pine bark can be rewetted by dunking the pot in warm water for 30 minutes or so. Few drops of natural soap (soap is a surfactant) can speed it up considerably but I suspect it might also damage the fine hair roots. I do not use it.

    Avoid any water retaining polymer granules in soil mix. It does increase water retention, does not make pine bark any better at holding water. But it will alter the perched water properties negating any positive aspects of a well prepared mix.

  • tropicofcancer (6b SW-PA)
    3 months ago

    Dylan, that is wood chips of eucalyptus. It may degrade much faster but I am not sure. It is quite intensely fragrant too (the oil). It is possible that it might have detrimental effects on plants. Again not sure about it. Look up allelopathic effects of eucalyptus to get an idea what you may encounter. I did find a few articles but did not read them properly.

  • Sergey Varlamov
    3 months ago

    Dylan - Thanks a lot for navigating to turface in Oz! Rate find indeed! Co-incidentally, once in a long while I will be driving through Melbourne in a few days so may as well pick up a bag of it as shipping to Sydney is expensive.

    BTW, I use Amgrow Wettasoil surfactant from Bunnings regularly formy gritty mix. Many of my plants are succulents which soil stays completely dry for days if not weeks so it is really hard to wet it. I lost quite a few plants cos water was not getting to rootball at all but drained around it. I have to either use bottom watering or 2-3 drops of Wettasoil per 1 L to help. Cheers, Sergy

    tapla thanked Sergey Varlamov
  • Dylan
    3 months ago

    I made my first batch of gritty mix today. Which was a mammoth task. 120L (32 gallons) which took a few hours.
    I’m not entirely happy with it. I think I screwed up the screening process.
    I screened the 6mm (1/4) particles no problems but when I went to screen the second time for the 3mm (1/8) particles, almost all of the 6mm (1/4) particles fell through into the mix also. I’m not sure what I was doing wrong. It might have been the screen I made or the way I was shaking the screen.
    I ended up having to include the smaller stuff into my mix too (smaller than 3mm (1/8)) as I was running out of time. I did everything else correctly however and washed everything of any residue before mixing using a insect screen.
    Not ideal, but I think the mix is at least 75% better than the terrible soil mix that was suffocating my Lime tree before.
    24hours later and my lavender plant that’s using the same mix seems to be perking up again, so we’ll see.

    A little more practice I guess. If anyone has some pointers, I’d love to hear them.

    tapla thanked Dylan
  • Sergey Varlamov
    3 months ago

    Dylan - If you want a meaningful feedback from anyone, it would be better if you took a closer shot so that one could see what particles are there, and placed something well-recognisable for a scale. Not a coin though as not everyone keeps international currencies :), but something universal like a pencil, ballpoint pen, etc.

    What is that white stuff, perlite? Looks sort of too fine to me for gritty mix. The other stuff looks quite fine too although hard to judge without a scale. I sift my soil mixes to size 2-4 mm using bonsai sieves from ebay, eg. https://www.ebay.com.au/itm/Kaneshin-Bonsai-Tool-Soil-Sieves-with-3-nets-No-145M/193366752997?hash=item2d058e7ee5:g:at8AAOSwDXJa10i4

    Attached are a couple of my samples of baby-succulents in gritty mix: red is seramis, brown - pinebark, white/grey - zeolite; in 6cm wide pots.

    Just advice: don't make too much of soil mix at a time cos if it's not good it will be a lot of a waste; 3-5 L at a time is good enough. Cheers, Sergy

    tapla thanked Sergey Varlamov
  • tapla
    Original Author
    3 months ago

    Over the years, I've saved a ton of word documents that answer common questions. One of those documents is about particle size:

    Particle Sizes (ideal)

    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.


  • jbclem
    3 months ago
    last modified: 3 months ago


    For cutting down the size of bark, when I can't find anything but medium bark (1-2"), I've used an electric shredder. I found a used Sun Joe shredder for US $20, it's the exact model shown in this link: https://www.amazon.com/Sun-Joe-CJ602E-Electric-Chipper/dp/B01HS59U28/ref=sr_1_2?dchild=1&keywords=electric+shredder&qid=1584308872&sr=8-2.

    It's a fairly useless shredder for anything else, and clogs easily, but you can feed the bark chunks into the slot and run them through two or three times to get smaller sizes. You don't get many chunks, mostly shredded bark, but at the time I was happy to have anything bark-wise. I've also cut open the narrow feeder slot as much as I could, and removed the thick rubber protective curtain below the slot to try to make it easier to feed the bark into the device. I haven't tried these modifications out yet because I found a big box (Lowes) source of what's called "groundcover bark", also mostly shredded bark, and have been using that.

    I've also read of people placing a pile of the larger bark pieces(in a bag?) on the driveway and running a car (tire) back and forth over them to break them into smaller sizes.


    Topanga, Calif.

  • Dylan
    3 months ago
    last modified: 3 months ago

    Good point about the scale Sergey. Everything is of the correct size. It's not perlite. It's rock from the nursery, and it's the correct size at about 3-6mm and not porous so it wont hold onto any water. In fact, my front yard is full of it, so it's always there if I ever need it. Perfect for allowing water through the pot.

    The only thing thats undersized is the bark - which was something I couldn't really control. There are some fines mixed in, however the bulk of it is about 4-6mm. Not sure if it was the bark I used or the process of my sifting, but it happened.

    However, I've struck gold today and found a supplier that sells bark for Orchid growers in bags. They sell them in bags at all different sizes (including a range of 3-6mm!), so I won't ever have to go through the process of wasting 4 hours of my time sifting for good bark and wasting all the bigger bits ever again!

    Thanks for the advice on the excess mix. I didn't make more than I needed however. This pot alone was 120 litres!

  • WMS Lee
    2 months ago

    I'm having trouble loading the comments. When i click "see [991] more comments", the webpage becomes blank. Is anyone else facing the same issue?

  • tapla
    Original Author
    2 months ago

    I'm working on reposting the thread - I'll see if I can get it done today. Thanks for your interest.


  • tapla
    Original Author
    2 months ago
    last modified: 2 months ago

    This thread has become unwieldy and the last 2/3 of the original post are often overlooked because one has to find/ click on fairly obscure links to access the rest of the file, which was too large to fit in the original text box. Please follow the link below to the new thread. Thank you!


    And thank you VERY much for your interest!