You might make a short jaunt over to the container gardening forum, where you'll find literally hundreds of posters that use soils with various bark products in it. I would note though, that pine bark usually doesn't 'shred', it flakes off in flat pieces or nuggets of various sizes.

I have used both uncomposted and partially composted bark in various soils for nearly 20 years with no problems at all. Pine bark is used extensively by nurseries in their soil mixes because it remains stable much longer than finer particled soil ingredients like peat, compost, and coir, while also adding a considerable degree of aeration and longevity to soils that cannot be achieved with mixes primarily comprised of peat/compost/coir and perlite.

IOW, it's good stuff.

Al

Here is a link that might be useful: More help here

Thank you for your kind and informative responses.
To be honest, much of the contents of the bags I bought were the flakes that you speak of that would typify ground pine bark. There were also other, I guess pine bark by-products, mixed in.....some small twig/branch pieces.
I ran the entire bag contents through a chipper/shredder of my own to get the 'coarse soil' consistency that I wanted.
I'm hoping that this will do the job as a base for our soil mixes.
I will be using it with Bonsai trees and my wife with her house plants. We will vary our individual mixtures based on the application they are designed for.
Thoughts?

Regards,
Len

Pine bark is rich in lignin and the lipid suberin. Both resist the efforts of micro-organisms to cleave the hydrocarbon chains the bark is made of. Though heartwood and sapwood contain a fair amount of lignin, they are more cellulose than anything, and break down quickly, which causes N immobilization and a more rapid collapse of soil structure, not a desirable characteristic for bonsai. Other 'forest products' mixed into the bark can also be a problem. Hardwood bark can bring high soluble salts levels and a pH spike during the composting process, so using a product that is as close to 100% pine or fir bark as you can find is to be desired.

I have ferreted out multiple sources for bark, so I have lots of options. I grow my short term plantings, like the garden display containers & veggies in a mix of 5 parts partially composted pine bark and one part each of sphagnum peat and perlite. I often find myself adding a little more perlite if the bark is very fine, but most have the opposite problem,. which is finding bark fine enough or bark that is partially composted. It's not necessary that the bark is partially composted; however, I just prefer it for it's water retention.

For bonsai and all my long term plantings, I use equal parts by volume of

Screened Turface
Crushed granite - grower size, or #2 cherrystone
and 1/8-1/4" fir or pine bark.

Al

The 5:1:1 mix I use is in the center here, fir bark at the top, and various other uncomposted pine products at 3,6,& 9:

{{gwi:2389}}

and this just lifted future bonsai is in the 1:1:1 gritty mix:

{{gwi:7488}}

{{gwi:1295}}

Most people who look at the gritty mixture think you could never grow anything in it, but I guarantee that if you follow a few simple guidelines, that it will outperform (by FAR), peat/coir/compost-based soils. It's great for long term plantings like houseplants, cacti, succulents, trees, shrubs, because it retains it's structure and guarantees aeration indefinitely. The planting being root-bound is a factor long before the thought of soil collapse would even cross your mind.

Al

OK Al -
My bark is more towards the 1/16" - mostly 3/16" and some
1/8" pieces. I intend to use Turface and Aquarium "soil" which is also a clay based substrate to "lighten" or aerate the mix. This inorganic medium is in the 1/8" size and very uniform in size. Do I need to get larger diameter bark to make this work? My bark resembles your Gritty mix in the middle but with finer small pieces and not as large big pieces.
I just don't want to defeat the purpose by using what I've got just because I made it a bit too fine.
Again, this will be used by me for Bonsai trees, both indoor and out, and also by my wife as a general potting mix. She will not be using the clay based medium but will use Perlite instead.

Actually, the height of the perched water table diminishes as particle size increases, until the particle size approaches about .100", or a little under 1/8", which is the point where perched water disappears entirely and you get maximum water retention w/o perched water. Even in consideration of the fact there is no perched water at these larger particle sizes, you can still alter or adjust the soil's water retention by varying the amount of Turface-like material and granite-like material. That's why it's good to have 1 mineral component that has lots of internal porosity and holds lots of water in those internal pores, and a mineral component that has no internal porosity.

The soil would work best if the mineral component is around 1/8" and the bark is just a little larger - say up to 1/4". The only reason for that is it takes longer for the larger bark particles to break down to something less than 1/8" - to the point where (for bonsai soils used in shallow containers, it's important) the soil will begin to hold some perched water, but now we're really splitting hairs.

Turface and aquarium soil (if it's a Schultz product) are the same thing, which means you'll be sacrificing adjustability. If you can find Gran-I-Grit in grower size, or #2 cherrystone (look for it at rural feed stores that sell poultry feed and grain elevators that sell animal feed, I would encourage you to use it in the soil. If you can't find it, Haydite or pumice in an appropriate size would be a fair second choice. You'll find that the reduced water retention will mean more frequent watering is necessary, but plants really appreciate the additional gas exchange that the more frequent watering brings.

Additional questions/comments?

Al

I've come to the conclusion that I'm an idiot!!
I just have an enormous problem understanding this "Perched Water".
Let me just say that if I take a clear cup with a hole in the bottom, fill it with turface and pour water into it, it will run through like there's nothing between the top and the bottom. The turface will hold moisture but there will be no standing water in the cup. Is this what you mean when you say, "....maximum water retention without perched water"?
I'm sorry if this sounds elementary to you and others, but if I'm to understand this I need to be talked to like I'm two. :)

A 'perched water table' (PWT) is the water that will not drain from containers because the particles are small enough to cause greater capillary pull/attraction than the gravitational flow potential. The height of the PWT is directly related to the size of soil particulates. As particle size increases, the ht of the PWT decreases until it disappears at around 1/8", but if you mix 25% 1/8" particles with 75% 1/32" particles, it won't change the ht of the PWT. This is why adding perlite to peat/coir/compost-based soils really doesn't do much for aeration/drainage.

Unscreened Turface will hold a considerable amount of perched water because of the % of particles it contains under 1/8", but Turface screened through insect screen holds almost no perched water. Mixed with the larger bark particles and the larger granite, it should hold no perched water.

The reason you cant use a peat/composty soil in shallow containers to good effect is because if that soil supports 3-4" of perched water (about right) and you use it in a 3-4" deep pot, the entire volume of soil will remain saturated after watering - not good for root health.

You understood the "....maximum water retention without perched water" comment correctly.

This is all explained in detail at the link I left above (in case you missed it).

Al

OK Al. I appreciate your patience with me on this.
The turface has been aged in a few different aquariums for years and the small particulates are long washed away.
I think that I can make this work so that the amount of standing water will be very, very minimal by using what I have, and adding the turface and some larger bark to the mix.
I will re-read the other article that you linked me to.
Again, thanks.