potting soil mix

walterupchurch(7)November 23, 2005

i am looking for a good potting soil mix for acer palmatum i am going to pot 500 this spring in 1 gal

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I planted my seedlings in the following mix 18 months ago and am planning to use the same when I repot next week:

3 parts Pine bark mulch
1 part sand
1 part compost (no animal waste)

    Bookmark   November 24, 2005 at 6:22AM
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sbeuerlein(zone 6)

For awesome discussions and advice on this subject, go to the container forum.


    Bookmark   November 26, 2005 at 12:39PM
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tapla (mid-MI z5b-6a)

Please - skip the sand and compost, they have nothing to offer containerized plants except problems.

You should have ready access to southern yellow pine bark fines from Southland Corp as (I believe) they are headquartered somewhere in SC.

I can offer help with good soils based on the bark as a primary component, but it would help to know if you intend to keep these trees or sell them, and how long they will be containerized before potting up.

Al (a denizen of the container forum)

    Bookmark   December 12, 2005 at 6:54PM
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schusch(Luxembourg z7)

Hello -
I read the thread in the container forum - with the contributions of Al and all others with great interest. I had also asked at the UBC maple forum a question regarding potting mixes for maples, where similar suggestions were made. A fir bark, perlite, loam mix was recommended, for instance (if I can post here a link to their website? http://www.ubcbotanicalgarden.org/forums/showthread.php?t=10132).

One problem I encountered with mixing soils was with the commercially available components. The pine bark mulch, for instance, was not composted - which may or, actually, may not pose problems from what I read. I have found composted spruce fines, sold as 'soil conditioners', with a ph of 7 - are these useful for maples - to add to the mix?
The pine bark pieces range from 0-1/3, then 1/3 o 2/3 here - in the end it'd be difficult to put them through a sieve to have an ideal size without wasting much of this good product. So if there are a fair number of 2/3 inch pieces, not necessarily that aged, would this have potentially negative side effects?
I know this information has been discussed but I found that looking at this crucial matter from all these detailed angles provides insight, and pleasure, too.
Thanks for any input.

    Bookmark   December 13, 2005 at 4:57AM
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tapla (mid-MI z5b-6a)

Here's my take on the soil thing (after reading quickly through the posts @ the link you provided):

As I see it, in the garden, soil is composed of many particles of varying sizes. Soil scientists have classified soil particles into three major groups: sand, silt and clay. Sand particles are the largest and tend to hold little water but allow good aeration. Clay particles are very small in size and tend to pack down so that water does not drain well and little or no air can penetrate. Silt particles are medium sized and have properties in between those of sand and clay.

A loamy soil, then, is one that combines all three of these types of particles in relatively equal amounts. Loamy soil is ideal for most garden plants but is death in containers. We might as well add sand to this discussion as generally inappropriate for container culture as long as we're discussing components.

Too, consider that loam doesn't mean the same thing in different parts of the world. In Japan, loam is a colored volcanic soil that collects in pockets on the sides of volcanoes. The Japanese often specify a color of loam as best suited to a particular tree type. Most often recommended for Acer, is red loam. I have no idea what loam might be in Schusch's neighborhood.

Container gardeners, especially those growing trees, would be well served to set aside the ideas that they need to "feed the soil", that "compost or sand is somehow a benefit to container culture", that "containers are just like growing in the earth", and that "what works in the garden should work in containers". Much of the knowledge we've garnered about growing in the garden should, in fact, be left there.

As a container gardener, your first and most important priority (all plants) should be to insure that whatever soil you use remains well-aerated for the life of the planting. You cannot do it, and maintain optimum vitality, with a peat based soil unless you're willing to do a complete repot/root-prune yearly, and even then, the tree will begin to suffer toward the end of the growing season.

The only potential benefit that compost offers is what few micro-nutrients it holds. In exchange for the nutrients, are you willing to use a pore-clogging mix? Compost compacts readily & will fill macro-pores quickly as it breaks down. There are many chemical and organic sources of micro-nutrients on the market that will deliver the goods w/o the sludge.

Those who tout sand as a drainage enhancer, are indeed correct. However, while enhancing drainage, sand also clogs valuable macro-pores and destroys aeration. The proper sized sand for container culture, trees in particular, would be about BB size or slightly smaller.

If you experiment with growing in a soil that is primarily inorganic, you will find it far superior to an all organic mix. Conifer bark is highly suberized and breaks down slowly, making it ideal for use in containers. To address the composted/uncomposted concerns: Uncomposted bark products will usually require additional N applications or a fertilizer higher in N. It's easy to learn the symptoms of N deficiency & adjust your fertilizer program appropriately. Other inorganic components may vary by geography, but a little searching will usually uncover a suitable product.

My Acer soil is my basic mix for trees. It consists of equal parts of pine bark fines, crushed granite (chicken or turkey grit - depending on plant size), and Turface (a hi-fired clay, almost a ceramic, that is superb at holding nutrients and water. This soil will retain its structure long after the plant is in need of repotting/root pruning, when it automatically gets new soil.


    Bookmark   December 13, 2005 at 12:13PM
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schusch(Luxembourg z7)

Thanks, Al, for the generous reply and clarifications.
One challenge is always to find and experiment with locally available product. I have a small question regarding size of the particles: what is BB size? ( I know of BB guns - does this mean we are talking 2-3 mm?)
Thanks again.

    Bookmark   December 14, 2005 at 4:04AM
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tapla (mid-MI z5b-6a)

Schusch - Yes. The "sand" we need to use in containers should be something that doesn't compromise aeration while facilitating drainage. To do that, a larger particle size is needed. Though you're in Europe, here in the US we can bey a product called Starter or Grower grit. It is fed to fowl to help them grind their food in the gizzard. It is comprised of screened particles of crushed granite, irregular in shape, with rather sharp edges, and the good news is it sells here for about $5 for 50 lbs. It is excellent at holding soil pores open and as a drainage aid. It also promotes root division.

Some of you might not know that the finer your trees root ramification, the finer your branch ramification will be. This is a big plus in containerized trees and helps offer more (pruning) opportunities for you to keep your tree compact (if you choose) while retaining a natural shape. Though I have never read the scientific reason for this, I have observed it for years first hand, and it is commonly written in books about bonsai culture.

You guys growing trees in containers are only a few turned pages or a club membership away from becoming bonsai enthusiasts anyway. ;o)


    Bookmark   December 14, 2005 at 7:36AM
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smalljaw(z 6b mid TN)

A lot of growers in TN. use dirty sand which comes from the sandstone area of the Cumberland Plateau . It is kinda gravelly . Aged pine bark is a must . I see perlite as well , that is readily available . Don't huff it , the grit is good . I am using a little amount of high dollar worm castings just to make me feel better . Some roots mychorhizza as well . Some with and some without , see what looks better in a year .

    Bookmark   December 18, 2005 at 2:20PM
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tapla (mid-MI z5b-6a)

I agree that aged conifer bark is to be preferred over fresh, but the only thing I've encountered when using the fresh bark is that the soil/plant combo will likely be extra hungry for N. The picture below is the soil mix I use for maples & nearly all deciduous trees. It will hold moisture, air, and nutrients well, while retaining its structure for long after the need to repot has come & gone.

I use a similar soil in raised beds. In this soil I have added finer sand and peat without concern for compromising aeration/drainage (further indication that growing in the ground is a completely different culture than growing in containers). The soil in the next photo is pine bark, peat, Turface, crushed granite, and sand, after 5 years in the raised beds. There is no natural soil component in this soil. It is all from scratch. Though it's tremendously fertile and alive, and an absolutely superb soil in raised beds, it would be slow, but sure death to plants in a container.


    Bookmark   December 18, 2005 at 3:01PM
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schusch(Luxembourg z7)


if I understand correctly, the difference is you use sand, and peat in the raised beds (and grit, Turface, pine bark in containers). Why the sand ? why the peat?

Thanks for posting the pics. If I identify these correctly: the white grains are perlite (or Turface?), the beige ones grit and the brown/dark ones the pine/fir bark?

    Bookmark   December 19, 2005 at 7:40AM
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tapla (mid-MI z5b-6a)

When I first built the beds, I used uncomposted (fresh) southern yellow pine bark. I knew that when I mixed in the grit and Turface, that the soil would drain too quickly, but also that the grit and Turface would be needed for drainage/aeration as the soil decomposed (remember, I'm growing mostly stuff that doesn't like wet feet). The peat helped to fill in some of the macro-pores & gave the soil better water retention until it began to compost. The sand is used because it initially helped to reduce pore size and is now aiding in drainage. I don't worry about aeration in the raised beds, because the continual capillary pull of soil under the beds, coupled with the pull of gravity, acts as a wick & completely removes the PWT. In a raised bed, the soil remains fluffy & well aerated, but it would quickly compact in a container.

No perlite in the first photo. The flat, brown flaky pieces are uncomposted southern yellow pine bark. The tan pieces are Turface, after being screened through insect screen to remove the fines, and the white pieces are grower grit, crushed and screened granite.


    Bookmark   December 19, 2005 at 3:22PM
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tamukeyama(z6 PNW)


A picture is truly worth a thousand words.

I was just getting ready to ask about raised beds. I'm planning on building a small bed this spring for a few of my trees in hopes of getting sturdier, thicker trunks in less time. My potted maples just aren't as happy as the ones I have planted in the ground.

So, you wouldn't use any native soil in a raised bed situation at all? Or, are there circumstances where you would consider it?

Next, all I have to figure out is where I'm going to find Turface. Some preliminary calls around town have yielded zip.


    Bookmark   December 19, 2005 at 11:48PM
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tapla (mid-MI z5b-6a)

Oh sure you could use native soil in the beds. If it's rocky, remove the big stuff. Amend well with compostable materials. The pine bark is great because it breaks down slowly. There are still sizable chunks in mine after 5 years. I was going for a highly aerated soil to insure best root growth, which translates into faster development and a more vigorous plant, overall. All I did was add ingredients that make a highly organic soil work as it breaks down. Actual soil composition is far less critical when growing in the ground compared to container growing.

I often end up trying to locate a source of Turface for those who write me off forum. I've never called Profile to try to find distributors & from there go to suppliers, but it would likely yield results. I'm going to call them next time I think of it to make sure it's not a goose chase.

What large city do you live near? If there is an active bonsai club near you, any member would likely have a source or two.


Here is a link that might be useful: C'mon! Let's go see what Profile Corp. has to say about distributors.

    Bookmark   December 20, 2005 at 7:15AM
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tapla (mid-MI z5b-6a)

I called Profile today and talked to a customer service rep. She assured me that if you call, they will provide the names of any/all distributors near you. If the distributors happen to be wholesale only, ask them for a list of their customers.


    Bookmark   December 20, 2005 at 3:24PM
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acernut(z8b CenTX)


How do you like polymer crystals?

    Bookmark   December 22, 2005 at 12:11AM
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tapla (mid-MI z5b-6a)

I have so many containers, and the soil I grow in is so open, that it's a given that I'll need to make the watering rounds daily, for some plants more frequently (in the middle of summer). For that reason I don't use them - no advantage to me, but they can certainly be a benefit to those that wish to grow in a more open soil but cannot spare the time to water so frequently. A small quantity of the crystals hold lots of water & interfere little with aeration, so it's win/win in my estimation.


    Bookmark   December 22, 2005 at 9:12AM
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acernut(z8b CenTX)

How about the impact on symbiotic microorganisms (bacteria and funghi) when using an inorganic mix? I saw one study that showed some plants spending (IIRC) 1/4th to 1/3rd of their energy feeding the soil (i.e. microorganisms) around their roots. The microbes don't just help w/ nutrition, but also with fending off disease. Doesn't seem like an inorganic mix would be entirely hospitable to the beneficial microbes.

And Acers, in particular, appear to be heavily reliant on the symbiosis w/ mychor, right?

    Bookmark   January 1, 2006 at 12:57PM
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tapla (mid-MI z5b-6a)

First, I'd ask for clarification that the study pertained to containerized plants. Then, should we consider that most in situ soils are primarily inorganic - 10% organic being a fairly rich soil?

It's true that plants devote energy to maintaining the mycorrhizal relationship. In the case of Acer, it's known that both endotrophic and ectotrophic myc. form root relationships. How important is the relationship? First we'd need to agree that a container environment is not favorable to myc. colonization. I have not found that to be the case. When I repot in spring, I often find visual evidence of hyphae throughout the soil. Then, even if we concluded that a particular soil was not favorable to myc. development, we would need to determine how important myc. actually is in containers. (As I thought about this last sentence, it occurred to me that if the soil is not conducive to the colonization of myc. it could very well be true that even though it might be adequate, perhaps it is a less than ideal choice to grow trees in.)

There is some evidence that myc. uses carbohydrates from the plant and helps fend off root diseases. Perhaps they secrete fungistatic compounds that discourage competing fungi and favor protective organisms. I have never read anything definitive in this area. The open & highly aerated soils I use practically eliminate the main source of root issues in containers. i.e. lack of aeration/poor drainage/over-watering, listed together because they usually are inextricable, one from the others.

My opinion is: myc. symbiosis is certainly very beneficial in containers, but not nearly as important as the relationship with in situ plants. Since the primary benefit of the relationship is the enhanced ability to extract water/nutrients from soil, our ability to make water and nutrients (through our fertilizer supplementation) probably make up in large part for any lack of myc. relationships. I need to pause here to say again that the relationship, in all likelihood, is there unless the cultural conditions we provide are not favorable. If the case be made about the structural enhancement myc. provides to in situ soils, again, we can turn to the consideration given to structural integrity/longevity of the soils I use.

The fungi are in the air everywhere & if the soil conditions are right, it's just like someone said of Las Vegas when questioned about building a city in the middle of a desert: "If you build it (a favorable soil), they will come".


    Bookmark   January 1, 2006 at 2:40PM
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I would agree with Al. There is very little to support adding myc. to potted soils unless the conditions are constantly controlled to meet the needs of the organisms--they can quickly be killed off and our investment in money and time to add them to the soil is lost. With inorganic mixes we will need to add fertilizers frequently. If not dilute enough the fungal organisms will certainly suffer. Attitionally, in hotter growing environgments, the pot temperatues can frequently exceed the moderate soil temperatures needed to keep these organisms happy. In controlled growing operations there may be some warrant to using these organisms to grow bigger stonger plants faster, but it remains unproven whether or not a collector can benefit from this same system.

Take in to account that a plant relying on a symbiotic relationship with these fungi over a period of time will suffer should they be erradicated. In a container situation, suddenly the plant will be forced to maitain a canopy that was supported by a symbyosis that no longer exists. In hot climates, trying to maintain benifical fungal colonies in containers is a certain failure over time and the cost to benefit for us is greatly weighted toward cost.


    Bookmark   January 1, 2006 at 3:01PM
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dsb_22(7 VA)

Al, everyone,
over the weekend, I found Espoma soil conditioner (similar to Turface), shredded pine bark, and chick starter scratch. I mixed up a batch of soil and repotted a small japanese maple and a cardinal candy shrub. They seem to be doing great, even though I removed almost all the old soil from their root systems and rootpruned the jm a little.

However today I noticed that the soil has a very strong, decomposing-type odor. I reread the posts above and realized that the starter scratch I purchased is not crushed granite. I didn't specify that when I asked for chick starter scratch...what I got looks more like chicken feed to me. I think that must be the cause of the smell.

So, feeling silly here...should I repot? Not concerned about smell as much as the quality of the soil. Also, I'm not sure when I can get back to the source of the starter scratch--would it be okay to sub perlite for crushed granite?
Thanks a lot

Thanks a lot

    Bookmark   April 4, 2006 at 8:26PM
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I have seen the following formula for an excellent container soil mix. I haven't tried it yet, but it was recommended by someone who had used it with success:

3 parts pine bark fines
1 part spaghnum peat moss
1-2 parts perlite (or vermiculite)

Translated to large batch, this would be:

3 cubic feet of pine bark fines
5 gals of spaghnum
5 gals of perlite
1 cup of lime
2 cups of fertilizer (controlled release)
1/2 C. micronutrients

    Bookmark   April 5, 2006 at 11:10AM
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tapla (mid-MI z5b-6a)

DSB - Yes, you should repot to a more appropriate mix ASAP. BTW, the soil amendment you probably wanted was starter grit, instead if scratch (which is feed and will create various problems in container soils).


    Bookmark   April 5, 2006 at 2:24PM
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dsb_22(7 VA)

Done--thank you.

    Bookmark   April 5, 2006 at 9:43PM
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In light of the recent thread regarding growing maples in containers, I thought the discussions in this older thread would be appropriate to resurrect :-) The principles don't change with time - they just get more validation.

Hope this is helpful.

    Bookmark   March 28, 2009 at 11:29AM
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