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Container Soils - Water Movement & Retention X

tapla
12 years ago

I first posted this thread back in March of 05. Nine times, it has reached the maximum number of posts GW allows 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 nine threads and nearly 1,500 posts 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; my wish is that you find it worth the read.


Container Soils - Water Movement and Retentioncolor>size>

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 (partially composted fines are best)

1 part sphagnum peat (not reed or sedge peat please)

1-2 parts perlite

garden lime (or gypsum in some cases)

controlled release fertilizer (if preferred)

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 - provided in some fertilizers)

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 superb soil that is extremely durable and structurally sound. The basic mix is equal parts of pine bark, Turface, and crushed granite.

1 part uncomposted screened pine or fir bark (1/8-1/4")

1 part screened Turface

1 part crushed Gran-I-Grit (grower size) or #2 cherrystone

1 Tbsp gypsum per gallon of soil

CRF (if desired)

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.

Posting IX

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Posting I

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

Al

Comments (153)

  • mainegrower
    12 years ago
    last modified: 7 years ago

    Thank you, Al, for your detailed answers to my questions. All that you wrote makes perfect sense, especially your noting that the natural acidity of peat in commercial mixes has already been neutralized.

    One further question. I've used Turface for quite some time and I've always assumed that it mostly retains water on the surfaces of the individual particles. Now that I think about it, it's obvious that it also absorbs a good deal of water internally. Under what conditions in a mix does it re-release the water?

    Finally, (and again apologies if this has already been mentioned), if anyone is having trouble locating Turface two excellent sources are companies which specialize in athletic field and/or golf course maintainence. Your local rec department, school system, or golf course can probably give you with the name of their supplier. I've found these companies very willing to sell a few bags to an individual gardener.

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    Plants absorb water a molecule at a time from the surface of Turface and other particulates. They also absorb the water Turface gives up in vapor form. Turface gives up its water to roots, and via diffusion, to other nearby particles with low moisture content.

    One of the nice things about The gritty mix is - even if the bark gets dry enough to become hydrophobic, the Turface still absorbs water immediately, which allows water to diffuse into the bark and 'break' any hydrophobic tendency.

    Thanks for the tip on finding Turface.

    I just finished 11 straight hours of repotting deciduous bonsai material - many were maples ........ and my tail's draggin'. Now I get to make another batch of soil after I eat so I can do it again tomo. ;o)

    Take care.

    Al

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  • acidic_luke
    12 years ago
    last modified: 7 years ago

    Al,

    If i use perlite in the gritty mix instead of crushed granite, do i still need to use gypsum? Also, do you recommend washing the perlite before mixing in with turface and bark?

    Thank you

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    Yes - use gypsum ...... and it's helpful if you rinse the perlite if you suspect or know the plants you'll be growing are intolerant of fluorides.

    Al

  • acidic_luke
    12 years ago
    last modified: 7 years ago

    Al,

    I finally got my gritty mix prepared. All i have to add in is gypsum (which i have) and slow release fertilizer.

    My question is if i add in the gypsum, do i use epsom salt with the first watering or the next time i use fertilizer which will be couple of months out.

    Also, do you recommend using epsom salt for a citrus tree in the ground (no gypsum used).

    And my final question is, would it be ok if i did not add the fertilizer into the mix right now and used on on the surface in a couple of days, and i could add the epsom salt at the same time.

    Thank you for your help AL.

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    Add it with the first watering, then each time you fertilize after that.

    I'm not an advocate of using soil amendments or fertilizers that target 1 or 2 specific nutrients unless you know from a soil test that those nutrients are the only ones that are deficient. Unless you know Mg to be deficient it cannot do your plant any good, and in excess, it can cause (antagonistic) deficiencies of other elements, Ca being the primary concern.

    CRFs are better if incorporated rather than broadcast. The reason is, they are almost entirely dependent on temperature for release and any direct exposure to sunlight will cause them to release much more fertilizer than the would if incorporated.

    Why not skip the CRF altogether and establish a regular regimen of applying soluble fertilizers.

    Al

  • scubastan
    12 years ago
    last modified: 7 years ago

    Hey AL:

    Wondering if you might be able to help with some recommendations into drip irrigation.

    Current setup.
    Citrus trees planted in 15 gallon containers with gritty 1:1:1 mix.
    15" diameter
    17.5" deep

    What kind of GPH do you think would be adequate and what type of Drippers or sprayers?

    Hmm also the number of Drippers or sprayers?

    Thanks in advance for any help.

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    I don't use drip irrigation, so I'm certainly no expert, but it would seem that the GPH rating wouldn't matter much if you have a time(r) setting. If I was setting mine up, I would probably try using the lowest GPH spray fitting (1 or 2) and adjust the time. Water diffuses laterally quite well in the gritty mix.

    Al

  • granburyflowergirl
    12 years ago
    last modified: 7 years ago

    Al, I finally located all of the gritty mix ingredients (phew!), I am very excited about making my first batch but I have a couple of questions:

    1) you said the first picture above was gritty mix so I am aiming to make something that looks like that but it looks like it has vermiculite or something else in it, is there anything else besides pine bark, turface and gran i grit? I haven't looked at the gypsum yet, is that what I am seeing in that pic?

    2)now that I have a clearer idea of how big these bags are and what they cost, I am concerned that my planters (don't laugh) may be too big! I have 4 planters that are 30" tall and 24" diameter, I plan to use them at the posts of my pergola (which sits on top of a paved patio) and grow clematis vines in them to cover the pergola. I thought the height of the planters would give the clematis a nice head start to the top of the pergola but now I am thinking that's a lot of space to fill with a costly mix if it isn't necessary (I don't know how deep clematis roots really get, so maybe it is necessary?) I thought about filling the bottoms of the containers with 1" stones - would that screw things up? What would you recommend?

    3) given the size of my containers, do I have more flexibility in the size of the pine bark?

    Thanks!
    Nik

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    That's a batch I made for someone else, and it did have a small fraction of vermiculite in it because she was worried about there not being enough water retention. I added it only to assuage her apprehension. ;o) Don't tell her I said that! I don't use anything in mine other than the 3 primary ingredients + gypsum.

    Have you bought the clematis yet? If you do some research on the plant, you'll find that they generally don't tolerate warm soil temperatures well. I usually even suggest that when planting them in the ground, they should be planted where their roots are shaded - often suggesting that a bush or shrub should be planted on the south side of the clematis to help keep the roots cool. I guess what I'm saying is you may wish to rethink the plant material if there will be any sun load on the containers or on the pavement in the near area of the containers.

    There is no reason you can't use something like the 5:1:1 mix if you wish. If you're going to use a very large pot and a small plant, it's pretty important that you use a well-aerated soil, though. The roots of even plants that are noted for their normally shallow root systems will fully colonize even the deepest container, as long as there is a favorable ratio of air:water in the lower parts of the container soil. You might want to fill a couple of gallon jugs with screw-on caps with water and using them for ballast in the bottom of your containers. I assume you'll leave them in place over winter? If so, leave some air space in the container to allow for expansion when the water freezes.

    Anything else I can try to answer for you? ;o)

    Al


  • granburyflowergirl
    12 years ago
    last modified: 7 years ago

    Thanks Al,

    yes, I already have the plants and really no back up plan :-(.

    I posted to the clematis forum a while back asking for container companion plant ideas for shading the clematis roots (that's actually how I wound up here thanks to gardengal :-)).

    I never got any plant suggestions, but I was told that it isn't actually the heat that bothers their roots - its drying out. Mine will all be on a drip irrigation system so I thought I would be okay there. Please let me know if that is not correct.

    Re: the gallon jugs, would that be preferable to say 5-7 inches of 3/4-1" stones? I was going to use the gritty mix because I thought it would a)last longer in the container without having to re-pot, b) be more helpful in preventing over/under-watering and c)help keep the soil cooler. Are you recommending the 5:1:1 mix for these large containers instead?

    I sifted one bag of the pine bark mulch with a 1/4" screen and about half went through it - the rest is dime to quarter size but breaks fairly easily. I have a window screen to sift the 1/4" stuff and will probably end up with only 1/4 of the bag being between 1/8" and 1/4".

    Can I use some of the dime to quarter inch pieces in the gritty mix?

    I have a ton of this mulch, and I will be making both mixes and using the left overs for new beds in my yard so nothing will be wasted, I am willing to do whatever is necessary to get a perfect mix - I just don't want to do anything unnecessary as my time is short.

    Since you ask, why yes, there is something else! In all my reading I saw somewhere way back where you were helping someone with decorative container plant combo suggestions for shade - do you have any for sun?, I would love to see some of those pics and or get your suggestions. I have the 4 huge planters and 4 large hanging baskets all will be on an adjustable drip and 1/2 will have 50% shade the other half about 30% shade

    Thanks in advance for your patience with my ignorant self!!!!
    Nik

    I want to use the gritty mix

  • granburyflowergirl
    12 years ago
    last modified: 7 years ago

    oops, disregard the last sentence - poor editing (or maybe subliminal?)

  • grow-anything
    12 years ago
    last modified: 7 years ago

    Al, I used your 5.1.1 mix for re-potting all my seedlings after they sprouted. I now am re-potting most of my house plants and my new outdoor potted plants with it. So far it is working great. Two questions: I want to use this mix for cactus plants too is that acceptable? Also, I want to use the mix when I plant my tomatoes in the garden. I want to "backfill" or cover the plants with this mix too. Any problems with that plan?

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    GBFG - From an OSU article about growing clematis. You can find the entire text HERE

    "Site Requirements

    Clematis have a reputation for being difficult to grow, however, like any other plant, if their needs can be met by the site and proper care, they will thrive. Clematis require full sun to grow best (6+ hours direct sun per day) though some dappled shade during the heat of the day is beneficial. Flowers of some red and blue large-flowered hybrids and the bicolors fade badly if they get too much sun (such as 'Nelly Moser,' 'Hagley Hybrid' and 'Hybrida Sieboldiana') and these should be planted in eastern exposures or partial shade. The site should be open enough to allow for air movement around the plants. Soil should be rich and well-draining with a pH close to neutral (7.0). Though the plant's stems and foliage should be in sun, the roots like a cool, moist environment. With the exception of C. montana, clematis do not compete well with large tree roots. Most clematis will require staking so the twining leaf petioles can cling and climb upward, though some gardeners choose to let the plants sprawl over the ground, over woodpiles, other plants, etc."

    So do whatever you can to keep roots as cool as you can.

    Either the jugs or stones, even packing peanuts will work as ballast, though the peanuts are a nightmare to remove from roots @ repot time. The gritty mix IS a better choice, but I thought you were balking at it because of expense or perhaps the extra effort it can take ..... You can use some of the larger pieces in the gritty mix if you wish. I was just trying to keep you from using large pieces like the nuggets & mini-nuggets that are readily available.

    You can find some pictures of a few containers HERE. I use a LOT of different plants in my containers. For group plantings, I usually try to follow the Thriller/Spiller/Filler philosophy. I select a 'main' plant as the focal point. Often, it's something upright and large. There is an upright variegated oregano that is spectacular in containers for its height and nice foliage ...... and its willingness to grow like mad! ;o) I usually plant 1 very upright plant (cordeline, e.g.) then 1 or more cascading plants, depending on the size of the pot, and lots of fillers. Over the years, I've learned what poops out and what is durable. Also, how you treat the plants as far as pruning/cutting back and dead-heading has a significant impact on longevity and appearance as summer progresses. I had a Master Gardener bus load from a neighboring county tour the gardens last early fall, and they were all very amazed at how full & florific (is that a word?) the containers were in early Sep, when most containers would be ready for the compost pile.

    Let me know if you have more ?s after you review the pics at the thread I linked to.

    Grow-anything asked: "I want to use this mix (5:1:1) for cactus plants too - is that acceptable?" The gritty mix would be better, but if you screened the fines out of it, and added some very coarse sand (1/2 bb size or larger) it would work well for cacti and succulents. The 5:1:1 mix will hold a little perched water because of the peat and fine bark, so it's better to screen it for cacti.

    Also: "I want to "backfill" or cover the plants with this mix too. Any problems with that plan?"

    No problem, but save yourself some effort and just use pine bark. If you incorporate it into the soil, you may see some N immobilization, so you might need to use a fertilizer a little higher in N than normal.

    Al

  • grow-anything
    12 years ago
    last modified: 7 years ago

    Al, that is great. Thanks for the help!

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    You're very welcome. I do hope you found it helpful.

    Al

  • urbangardenfarmer
    12 years ago
    last modified: 7 years ago

    Hey Al, I am wondering which mix would work best for growing tomatoes and peppers in 18 gallon containers(2 plants in each container). They will be cycled with a timer on a drip system.

  • marcos_2010
    12 years ago
    last modified: 7 years ago

    Hi Al,

    I have 15 Heirloom Tomato seedlings that I have transplanted into 15 gal pots over the last several weeks. The potting mix is based upon your 5:1:1 mix but I haven't gotten the exact pine bark fines unfortunately. The first batch was made from Forest Blend mulch screened down to particle size >1/4", Some of the pots have wicks others are without. So I am confused. What would you suggest? I have Miracle Grow 24-8-16 and I bought 50 lbs of the MicroMax micronutrients. So I can switch to that. The MG is applied at 1 tbsp/gal and since I am fertilizing every time I water I can cut that in half but I am not sure at what strength to add the MicroMax. I am including a few pictures of the plants for you to see. Any other suggestions you can think of or am I just overreacting here?
    I am also attaching some pictures of the much older plants that I planted in last year's coir based potting mix. I do not add these because I am considering using this mix ever again, just to show the plants I started in November/December before I found this forum. I am going to be eating tomatoes in a month!! I put wicks in these last week and so far they are doing very well, lot of fruit set particularly on the Cherokee Purple, Beefsteak and Brandywine OTV. I do have to monitor them more frequently to see the moisture level thorughout the pot. The little plant is a Manitoba. I have had a great deal of Blight lately on the lower leaves and have to start spraying more frequently. I have been spraying these plants since they were little seedlings but in the last month have reduced the frequency a bit. I also think this could be an indication of the plants inability to take up nutrients in the coir soil readily because of the perched water.

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    UGF - I use the 5:1:1 mix for tomatoes and other veggies. I usually only use the gritty mix for long term plantings.

    Marcos - I had some trouble understanding exactly what you are saying, and I don't think you're over-reacting. I watch the color of my tomato leaves carefully, and when they are not dark green, I fertilize - especially if I see the older leaves are a little less green than those more recent. My thought is they are probably under-fertilized.

    Are you able to water copiously enough that the soil is being flushed each time you water? If so, I would double the fertilizer dose and see if that helps.

    Al

  • urbangardenfarmer
    12 years ago
    last modified: 7 years ago

    Thanks for the quick reply Al! Could I substitute mushroom compost for the peat?

  • marcos_2010
    12 years ago
    last modified: 7 years ago

    Al,

    I water so that it runs out of the drain holes in the pots. When I initially transplanted I really saturated each pot. Subsequently, I have been giving them a gal of water with 1/2 tsp of FP and 1/4 cup of vinegar each time. When I do this the water runs out the drain holes at the bottom.

    I will go to 1 full tsp of FP/gal of water in my next watering. I am watering every 4 to 5 days now.

    Thanks for the information. I guess I was a little verbose in my post but I wanted to give you all the info. Once previously you mentioned something about going to a urea based fertilizer if I was worried about a salt buildup. If I do, should I also top dress with MicroMax Microneutrients and add Miracle Gro to the water 1 tbsp/gal?

    Thank you again for all your help and guidance.

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    UGF - You can if you want, but I wouldn't be tempted to go beyond using it as the '1' fraction of 5:1:1, and it really doesn't offer any advantage over peat that would be significant enough that you'd notice. Remember - container soils are more about structure (a durable mix that holds favorable amounts of air and water) than they are about nutrients.

    Marcos - No worry about being wordy - it's much better to have too much info than to have to squeeze you for it. ;o)

    I don't think I would have mentioned any advantage in soluble salt levels for a urea-based fertilizer vs a fertilizer weighted toward nitrates, but I might have given it the nod for its ability to acidify the soil solution. Is that what you're thinking of?

    I usually incorporate Micromax, rather than broadcast it, but a cup is enough to treat 64 gallons of soil, so the math works out to about 3/4 tsp/gallon of soil.

    I don't remember right off hand what the MG dosage is, but you should be able to use half strength each time you water if you're flushing the soil well.

    Is the chlorosis more prevalent in the mix that has a larger fraction of sapwood? Did you mention what your soil temperatures are - a guess? - above 55*?

    Al

  • shlacm
    12 years ago
    last modified: 7 years ago

    Okay, here goes... I've been perusing this site for a couple weeks now, but just joined today! I have never been able to keep plants alive, I even manage to kill Aloe Vera plants!!! But after years of wanting to do so, I have ordered 3 (18"-24") blueberry plants! This site makes me quite optimistic.

    First, let me say that $ is a HUGE problem on this project. If the plants die, I'll probably never try another plant again, lol. I went shopping today and acquired the following: 2 cu ft Miracle Grow garden soil (couldn't find plain "dirt" lol), 2 cu ft pine bark mulch (I plan to sift out the smaller parts to use in my mix and use the bigger parts as... mulch), 3 cu ft peat (sphagnum) moss, 8 qts perlite, and 8 oz Miracid. I need to fill a 45 qt pot and a planter that I estimate to be about twice that size. I would like the soil mix to last 2 years.

    I am planning to use 1/4 dose of the Miracid weekly with epsom salt. Add vinegar to the water as needed. And it looks like I still need to find gypsum!

    So, a few lingering questions:

    Is all gypsum pelletized?
    I need a lot more perlite, don't I?
    Is this going to work, or am I way too far off base?
    And, should I get the mycchorizal stuff?
    How do I know when they need to be watered?
    Do I add vinegar to the water every time I water?
    How do I know when the ground is remaining above 55 degrees? Stick a thermometer in it???
    Am I missing anything???

    Thanks so much for taking the time to read my ramblings!

    Steph

  • shlacm
    12 years ago
    last modified: 7 years ago

    oh crud, I'm dumb, why did I buy dirt at all? Okay, so obviously that's got to go back...

  • granburyflowergirl
    12 years ago
    last modified: 7 years ago

    Al,
    I just want to thank you for your very informative and helpful response, the clematis info was very informative, I think/hope I will be okay given the size of the containers, their light color and dappled afternoon shade once my October Glory Maple leafs out.

    What great pics!!!! The planters are incredible and gave me some ideas -I would especially love to copy your yellow planter if you'll share whats in it (and if those will handle my zone). Your yard is incredible! Even the grass looks fabulous (what kind is it and what's your secret there?). Are those Thujas in the background?

    I will be back begging for more advice as soon as I am done with all of my sifting (should it take 2 hours to sift a bag of turface?).

    I'm thinking I should really just sift in my bikini on and get my tan while I am out there! Kill two birds with one stone ;-)
    THANKS!!!!!
    Nik

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    Steph - with those ingredients, you don't need gypsum, you need dolomitic (garden) lime. If you're going to need (about) 40 gallons of soil, you're going to need about 2 - 2 cu ft bags of bark and about 6 gallons of perlite. Your best bet would be to find it in a 3-4 cu ft bag at a greenhouse/nursery op. It will be a fraction of the cost of smaller bags on a per volume basis.

    I never use mychorrizal inoculations, but I see much evidence of the fungi's normal presence in spring and fall when soils are cool - none in the summer, however. Some people feel the inoculations do make a difference, so I'll let you decide on your own.

    You can tell if established plantings need water when a stick (sharpened dowel) comes out dry or the soil feels dry at the drain hole. You'll soon become familiar with the 'rhythm'. Newly established plantings need to be watered more frequently until roots colonize the lower parts of the container because the top of the soil drys out first, so keep that in mind.

    For the 55* thing, sort of take an average of day/night high/low temps. If the average is consistently above 55*, go ahead and fertilize.

    I'm sure there are things you're missing (questions left out), but that's what the forums are for. Stick around - as you think of them, just raise your hand & someone will call on you. ;o)

    Nik - I laughed about the bikini thing as I puzzled through how you signed off.

    Thanks for the kind comments about the yard. I do have a long row of about 50 Thujas separating me from the neighbor on the east.

    It takes about 15-20 minutes for me to screen 50 lbs of Turface, but I have done so much of it that I'm pretty organized .... & have built screens that make the job easier.

    Good luck with the tan. I've been spending so much time outdoors, in spite of the weather, that everyone is wondering if I just got back from a vacation a little more exotic than my front gardens. ;o)

    Al

  • shlacm
    12 years ago
    last modified: 7 years ago

    Thank you so much! One bit of clarification, if you don't mind. I thought I needed the gypsum instead of the lime for blueberries because of their "desire" for acidic soil???

    Oh, and (raises hand) I'm also wondering, when I screen the mulch, is it important to separate out the tiny bits as well? I mean, blueberries have shallow roots and the containers are fairly deep, so would the little stuff just filter down to the bottom and not really create a problem because of the shallow root/deep container situation?

    Thanks again!
    Steph

  • marcos_2010
    12 years ago
    last modified: 7 years ago

    Al,

    If I didn't know for sure, I do now about the urea based fertilizer. So it helps to acidify the soil! Got it.

    I fed and watered yesterday so I didn't want to try to take temperatures of the soil. I have a temperature probe that is sitting on about 65 degrees this morning. But these plants are inside a temperature control greenhouse that was 66 degrees when I went in this morning. It gets as high as 95 or so during the day even though I installed a thermostatically controlled attic vent fan and have 50% shade cloth covering the film of the roof. As soon as I am secure enough in no further frost, I will take the film off and just cover with shade cloth, like my hoop house.

    Yes, the plants in the highest percentage of sapwood are the palest. The color is poorer on the Potate Leaf varieties that Regular Leaf. The color is best on the last batch which was the fir bark chopped in a wood chipper. Is this the Nitrogen immobilization you talked about? I have Miracle Gro that is 24-8-16 that I can use on these earlier transplantings along with the MicroMax, if you think that will help. After I read you email yesterday, I went out and gave everything a full strength feeding of Foliage Pro, about half and the other Miracle Gro + a tbsp on Micromax(according to directions on bag). Did this on the big plants too.

    What do you think? Any further instructions?

    I'll tell you what Al. Gardening is fun even when you don't have a clue what you are doing. But it is so much more interesting to have a resourse such as yourself, that can expose the science and chemistry of plant biology etc.

    Thank you so much!!!

  • gonebananas_gw
    12 years ago
    last modified: 7 years ago

    The following quote is pretty much a horticultural myth (not a rarity in horticulture) and misuses the hydrological term "perched water table" and indeed even the term "water table." It's no big deal, horticulturists view soil water differently than hydrologists or soils physicists and can use less precise conceptual views. But in any case, particles slightly smaller than 1/8 inch in no way can support saturation against gravity, whether or not located above a layer of coarser material. Downward drainage simply slows down at that boundary (plausibly even enough to have some horticultural significance in extremely sensitive plants) but it by no means stops to support a perched saturated zone. Imagine a layer of BB's (about 1/8 inch diameter) above gravel. Could a saturated zone persist in the BB's? Much finer materials (silts, clays), though, can in fact hold a bit of saturated zone by capillarity above an actual water table. (Water table is defined by equality to atmospheric pressure not saturation; the capillary zone is actually under less than atmospheric pressure.)

    This would hardly be worth mentioning if the notion of a "perched water table" in containers had not been repeated and pointed to so many times. I think you will find that soil water specialists have a different view of the matter.

    "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."

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    Steph - You can use either gypsum or lime with the 5:1:1 mix for blueberries. You might find more helpful info if you click this link.

    Marcos - it sounds like you're on the right track. Nothing more to add at this point. Keep us posted.

    GB - It's easy to illustrate the statement I've used hundreds of times that goes something like, "The ht of the PWT is inversely related to particle size. As particle size increases, the height of the PWT decreases until at a particle size of just under 1/8" (around .110") it disappears entirely." You can illustrate it very easily in a practical application by noting a properly made gritty mix will hold no perched water, but the same soil made with unscreened Turface will.

    You can SEE it in a clear plastic cup. Turface screened over insect screen will hold perched water, as will crushed granite in starter size. Crushed granite in grower size holds no perched water; neither does screened Turface mixed in equal portions with grower grit.

    A BB is .177", almost half again as large as .125 (1/8)" and practically speaking we are discussing irregularly shaped particulates of a much smaller size that tend to nest with each other and produce smaller pore sizes than perfectly shaped large spheres like BBs.

    Common soil materials with an 'average' particle size of 1/8" (say an even distribution of 1/16-3/16") will hold some measure of perched water, while common soil materials with a uniform particle size of 1/8" will not.

    Al

  • greybird_keke
    12 years ago
    last modified: 7 years ago

    Hi Al,
    About six weeks ago (about the same time I started reading about your gritty mix), I purchased 18 various succulents from an older lady who at one time sold to the public, but apparently now she has trouble keeping up with the care of the plants and greenhouse. She sold me the plants for between 50 cents and $2 each - nice plants - but in TERRIBLE need of repotting and attention. The soil was so old and compacted that some of the plants had very few roots left - I was surprised they looked as good as they did. Anyway, I wanted to repot them into your gritty mix, but none of the suppliers in my area had ever heard of Turface, and I was unable to locate any crushed granite. Or the pine bark fines, for that matter! However, I was able to locate a product called "Haydite" in bulk, so I sifted that and mixed it 2:1 with store bought cactus soil. It is amazing how much better the plants look since they have been repotted! My question is, will this mixture be OK for awhile, or should I try to find the "real" ingredients and repot them again at the end of the summer?

  • shlacm
    12 years ago
    last modified: 7 years ago

    WOOHOO!!! I did it! Okay, so my mixture is actually 4:1:1, but I'm still pleased and excited! Mixing it was MUCH harder than anticipated, lol! (made about 51 gallons!!!) But, definitely gratifying! Now, I wish my blueberries would HURRY UP and get here!!!

    Thanks everyone!

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    Haydite is a brick-like material that has quite a bit less internal porosity than Turface, but more than crushed granite, so it sort of has the o/a porosity of the average between Turface and granite. The main issue I've always had with Haydite is finding it in an appropriate size.

    Don't take this reply as terse, please, but you'll need to decide how hard you want to look for the ingredients. Some people think it's well worth the effort, and others won't be bothered to go out of their way. We're all different. ;o) It would give me/us a better idea of how available these products are in your area, or what substitutes might be available if you included your state/USDA zone in your user info (like my z5b-6a MI) or what large city might be near you. Often you'll find someone following the thread who knows exactly where to find the material, and I usually poke around on the behalf of others to try to find the ingredients.

    FWIW - I have grown & propagated lots & lots of cacti/succulents in the gritty mix, .........

    {{gwi:2010}}

    {{gwi:3268}}

    {{gwi:5137}}

    {{gwi:3271}}

    {{gwi:5647}}

    ....... often in containers so shallow they would present problems when using heavier soils, and have find them incredibly easy to grow and keep healthy in it.

    Al

  • greybird_keke
    12 years ago
    last modified: 7 years ago

    Al,
    The Haydite is the proper size after sifting; if it is the average porosity of Turface and granite, would it be OK to use 2 parts haydite to one part bark fines? I could probably find the bark fines now that the stores are getting their new shipments in, but when I was looking for it before, the stores mostly only had last year's (frozen) leftovers. And these succulents were in desperate need of repotting! But I don't mind re-doing it if you think it would help. Your cacti and succulents are beautiful, btw!
    Thanks,
    Nancy

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    I think you should be in good shape with the Haydite at 2:1. Just take note of what the water retention is like. You might even wish to mix a small fraction of vermiculite into the next batch if you find it isn't sufficient. The only disadvantage of using Haydite + bark instead of Turface:bark:grit is that you lose ability to adjust water retention by varying the volume of Turface:grit. Other than that, it pretty much boils down to settling on an appropriate particle size for your needs.

    Al

  • urbangardenfarmer
    12 years ago
    last modified: 7 years ago

    AL, that last picture is amazing! It looks like there's more plant mass then root mass! I've gone against the mushroom compost. I'm sticking with your recommendations.

    I was wondering if anyone has used these nutrients before? I'm thinking of using them to grow my tomatoes and peppers in containers.

  • gw0x
    12 years ago
    last modified: 7 years ago

    Hi Al,

    I am new here, and I spent several hours reading through these posts. I am going with gritty mix. Hopefully, I will find them this week. I have a few questions and your help is appreciated.

    1) In one thread, you mentioned, dolomite is the most preferred (compared to garden lime and gypsum) because it contains Ca and Mg. If that is the case, why does the main article mention gypsum instead of dolomite ?

    2) Assuming I go with dolomite, can I use Foliage pro 9-3-6? Is that a "safe" combination ?

    3) How often do I need to add dolomite and FP ? Every week ? Every month ?

    Thanks.

    Jake

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    1) I suggest gypsum when making the gritty mix because of the gritty mix's higher (pre-lime/pre-gypsum) starting pH. Dolomite raises soil pH, but gypsum's effect is so minor as to be virtually unnoticeable. Generally, the 5:1:1 mix can benefit from the lime's function of both raising pH and supplying Ca/Mg.

    2) Yes - I and lots of others do it as a matter of course.

    3) Use dolomite or gypsum when you make the soil, and the FP as needed. I generally fertilize the plants I over-winter under lights every time I water with weak doses (12 drops/gallon) and weekly at 1/2 strength or stronger for plants growing outdoors. I would follow the same every watering program outdoors if it wasn't so time consuming. I tend more than 300 containers each year and I just can't find the time to mix and fertilize from a water can each time I water - which is daily.

    You'll find that the Mg fraction of dolomite is much more soluble (approx 125x) than the Ca fraction, so you probably wouldn't need to increase the Ca supply in the second growth cycle of plants remaining in the same soil, but you may need to supplement the Mg supply w/Epsom salts.

    Al

  • andersons21
    12 years ago
    last modified: 7 years ago

    I will soon be planting some roses in 20" terracotta pots on my deck. I would like to use something like the gritty mix, but lighter. The pots themselves are already so heavy. I found large bags of pumice locally, which I think seems a heck of a lot lighter than the granite would be. I read in another thread that pumice retains less water than Turface, but more than granite. Could I use 2:1 pumice:bark? What level of water retention would be best for the roses?

    I am excited about how I think the gritty mix (or similar) will solve so many problems I had in the past, but I am a little scared of the watering frequency.

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    You can try the 2:1, pumice:bark. I can't predict what water retention will be like, but you could always have on hand a bag of Turface or NAPA floor dry to up the water retention if you find it necessary. A small fraction of vermiculite would do the same thing, if you need it.

    Al

  • gw0x
    12 years ago
    last modified: 7 years ago

    So, I got all the ingredients. But, the Turface MVC looks very fine, compared to the granite and the bark. If the size is comparable, then I am doing something wrong. Can someone please confirm if the turface size is much smaller than 1/4 inch.

    Thanks

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    It is.

    {{gwi:5648}}

    It's about 1/8" and smaller - 1/16-1/8 if you screen it over insect screen.

    Al

  • scubastan
    12 years ago
    last modified: 7 years ago

    Hey Al,

    Question about the gritty mix. How diligent do I need to keep up with the fertilizer regiment?

    I have my nice Washington Navel Orange growing in the gritty mix for about 6 weeks now. It had a nice flush of new growth and lots of blossoms. However a hand full of leaves are now showing Nitrogen deficiency.

    My normal water schedule is Saturday I water with 1 gallon of water mixed in with 1 tsp FP. then I water again on Wednesday with plain water. My suspicion is that I might be washing out the FP with my mid week watering.

  • gw0x
    12 years ago
    last modified: 7 years ago

    Al,

    Thank you very much for your help. I have repotted the plants on gritty mix.

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    Scuba - You need to be reasonably diligent. During the summer, I usually water most of my plants daily or every other day. I normally fertilize weekly or every other week (depending mostly on temperatures), adding a tbsp of FP to each 2-1/2 gallons of water. You could reduce the dosage and increase the frequency if you wish. When I water, I usually try to evenly wet the surface of the soil with my watering wand, and I stop watering as soon as water starts exiting the drain. This is sufficient to adequately flush the soil of accumulating salts.

    Al

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    I forgot you for a second, Gwox. You're welcome, and good luck. Let us know how you fare, please. ;o)

    Al

  • tapla
    Original Author
    12 years ago
    last modified: 7 years ago

    The thread has reached 150 posts, so if there is interest, you can find the continuation at the link I've left below. Thanks to everyone for participating and for helping us all to learn.

    Al

  • HU-169271514
    22 days ago

    Isn’t this a rather lengthy way (and I do appreciate the science) of saying: a 2:5 ratio of perlite in your mix?

  • tapla
    Original Author
    22 days ago
    last modified: 22 days ago

    Not at all, and I don't remember writing anything that should leave anyone with that impression.

    If I had to identify the crux of the thread, it would be that to take advantage of highly aerated media and their sharp drainage, it's essential to start with a very large volume of coarse ingredients, and there should never be enough fine material to fill all the spaces between the large particles.

    When you add a marble/perlite) to a jar filled to the rim with sand or peat), aeration of the medium in the jar DECREASES, and continues to decrease as you add more marbles/perlite. It is only when you have added a volume of marbles/perlite) so large there is not enough sand/peat) to fill all the desirable pores between the large particles that aeration begins to INCREASE. This is called the "threshold proportion".

    Al