Wood pellets for substrate - anyone use them?

[Bonsai Nut]

I have recently been going on a deep dive with wood pellets as a soil component. They can be purchased in bulk as farm stock bedding (usually pine pellets) or as fuel pellets for wood stoves (usually hardwood pellets). These pellets are typically compressed sawdust that otherwise perform similarly to a core of the corresponding wood type. No additives (binders, fungicides, etc). No toxic chemicals (since they are designed for animal bedding or burning).

When they are moistened, they almost immediately break down into sawdust of the corresponding wood type. So at some level I'm wondering what the pros/cons are of using hardwood sawdust in your soil mix alongside pumice or other inorganic materials. I immediately worry about water retention... but then wonder how much different it would be from using pine bark fines(?)

FWIW mushroom growers use this as a stand-alone soil to grow food mushrooms. There are numerous YouTube videos out there. Mushrooms grow on damp (but not saturated) substrate - similar to rotting logs.



What happens when you water wood pellets:

 

[Gabler]

I'd be concerned about allelopathic chemicals in the sawdust if the sawmill was cutting black walnut or something.

 

[Flowerhouse]

In my distant past, I used sawdust from a sawmill as a soil amendment. I was using it to loosen up the clay in my central Kansas garden. The county extension office advised that sawdust uses a lot of nitrogen in the process of decomposition, so less nitrogen was available to plants. That's what I'd worry about in using sawdust for bonsai.

 

[Maiden69]

IDK, with coco coir available, why use saw dust? I use those pellets for my Traeger smoker, when they get damp they turn to mush. I guess you can call it sawdust, but it stays clumped up. At least you can shred coco coir and have it evenly spread on the soil.

There is a brand that sells actual wood charcoal pellets, and they state that they are damp (not sure if wet) resistant. Royal Oak, might look at that before looking at wood pellets. But again, might as well get biochar.

 

[Michael P]

Interesting. Do you soak them before mixing with inorganic components? The warning about nitrogen deficiency is valid, but in bonsai mix the proportion of saw dust would be low . And we can fertilize to compensate.

 

[stubmle]

If I recall right, our own @Leo in N E Illinois has mentioned using hardwood sawdust as a soil component for blueberry & other ericaceous plants. Something about myccorhizal development, I think.

 

[WNC Bonsai]

I would think it would clog your soil similar to using peat humus, as well as competing with your trees for nitrogen. I use composted tree bark (Lowes Natures Helper), and sift out the fines same as with my other soil components. Composting uses up some of the most labile organic matter and reduces the nitrogen demand.

 

[Wires_Guy_wires]

I have used them over a decade ago and I never used them again.
The particles are super small, comparable to sawdust you get from sanding. As opposed to sawdust from sawing, which tends to have more body.
The way they're pressed also tends to break rhe fiber structure so microbial life doesn't like living in it.

If you want to use it, 2-5% of your soil should be no issue. Anything above that, would be problematic.

 

[Leo in N E Illinois]

Yes, a small amount of hardwood sawdust is a recommended addition to growing mixes for commercial blueberries, and related ericaceous plants. Less than 5% by total volume, I always tried to estimate about 2 to 3 % by volume when I was potting up blueberry plants. The hardwood sawdust feeds the ecto-mycorrhiza, which are obligates for blueberry and many related species. Yes, sawdust can clog up drainage and air voids, in bonsai mixes one must decide whether one really needs the sawdust or not. I grow blueberries for fruit. Not really for bonsai. I use much larger pots, and blueberry species are very tolerant of water logged environments.

For bonsai sawdust might not be a necessary additive. Except when growing ectomycorrhizal obligate species like blueberries, certain ericaceous species and possibly some exotic Rhododendrons like Vireya. Generally for other species, it is probably not necessary. Maybe a nice additive, but don't add so much as to risk your air penetration. You don't want to "clog up" your mix if you don't have to.

In bonsai culture we tend to fertilize our trees, and especially if we use nitrates to fertilize out trees, the use of nitrates kills off a large percentage of mycorrhiza with each application of fertilizer. For most species of trees like maples and pines, this is not a big deal, as they can utilize the nitrates after bacterial reduction of the nitrates. As demonstrated by the great trees at shows, grown by many different methods, the most commonly grown species for bonsai are adaptable to getting their fertilizer in many ways. For most species of bonsai we really don't need to pay attention to growing the mycorrhiza, if our horticulture is "good enough".

In the case of blueberries, and ectomycorrhizal obligate ericaceous plants, these species CAN NOT absorb nitrates, and the presence of nitrate will potentially kill their obligate ectomycorrhiza, killing the plant if the situation lasts long enough. Blueberries get their nitrogen from amino acids and or ammonia or ammonium ions. This means fertilizer should be something like a fish lysate or a ammonium sulfate based fertilizer. No nitrates allowed.

Interesting thing, if you want to grow your mycorrhiza on your pines and maples and other species. throw out all your nitrate based fertilizers and only use fish lysates, (fish emulsion) ammonium based fertilizers and or cake type fertilizers if no nitrates have been added to the cakes. (soya bean cakes, sugar cane bagasse cakes, cottonseed meal cakes, etc. ) This is actually the traditional way to grow most bonsai, using cake fertilizers, and does promote long lived mycorrhiza.

Using nitrate fertilizers knocks back mycorrhiza with every application, requiring a week or more to re-establish after application. Just something to think about. If using nitrate fertilizers works for you, fine, there are many, many ways to raise a healthy bonsai, but if you want to try something different , switch to no nitrate fertilizer system. Cakes, or fish lysates or an ammonium sulfate based chemical fertilizer all can work.

Sorry, I may have rambled on a bit.

 

[Wires_Guy_wires]

Interesting thing, if you want to grow your mycorrhiza on your pines and maples and other species. throw out all your nitrate based fertilizers and only use fish lysates, (fish emulsion) ammonium based fertilizers and or cake type fertilizers if no nitrates have been added to the cakes

I got wildtype mycorrhizae from areas exposed to high nitrates and nitrites for decades, if not longer. They are unaffected by fertilizer and they do not form unbreakable bonds; meaning I can transfer them to new soils and they will colonize it.
I'm personally of the school of thought that takes the stance that not mycorrhizal connections are set in stone. With fungal diversity research expanding each year, and seeing how they fast they diversify in very, very small microclimates, I am unwilling to believe that there are set rules for mycorrhizal connections.
I reject the statement that endomycorrhizae and/or ectomyc. need to be there from the germination stage, I also reject the statement that fungus-plant-host connections are a 'for life' connection and are unable to be made later in the plants (or fungus') life.
In the lab I did some projects with fungus researchers who investigated pathogenicity and resistance acquisition from environmental factors and these guys agreed that essentially you could make any statement about fungi and be right. They're so diverse that it is objectively difficult to find a model species for any of the families. These poor guys were stuck in a pickle, since every sample they sequenced threw them off: huge inversions of the genome, huge deletions, sudden copy number changes, and random uptake of foreign genes made it difficult to even get a mapping against a genome (since the original one was built with shorter DNA reads that are glued together by a program, which "corrects" any gaps, duplicates and can't see whether or not something is flipped around or not).

I've advised some growers to just try nitrates and nitrites and see what happens. Most of them do report positive mycorrhizae presence after a couple years. That might be of some value for your blueberries! If When you find the right type, it might be cheaper to fertilize and it might be a universally applicable myc that could help host defenses, now armed with a nitrate/nitrite collection of molecules.

 

[Leo in N E Illinois]

@Wires_Guy_wires
You are right, I probably have been "talking out of my .....hat" when it came to extending my thoughts past commercial blueberry cultivation. So, all you pine and maple bonsai growers, ignore my bullshit as questionable.

However, I was a commercial blueberry grower for 5 years. Paid a $118,000 mortgage with the income from the harvest of the berries I grew. Did not have much to put in my own pocket when done, but I did cover the the core expenses. What I said is what was taught to me by the Ag Extension Services that provide assistance to farmers producing their crops. I do stand by the blueberry stuff. Nitrates are bad for blueberries. Period.

You are probably right about pines and maples. Sorry for over-reaching or over-extrapolating my thought process.

 

[Wires_Guy_wires]

@Wires_Guy_wires
You are right, I probably have been "talking out of my .....hat" when it came to extending my thoughts past commercial blueberry cultivation. So, all you pine and maple bonsai growers, ignore my bullshit as questionable.

However, I was a commercial blueberry grower for 5 years. Paid a $118,000 mortgage with the income from the harvest of the berries I grew. Did not have much to put in my own pocket when done, but I did cover the the core expenses. What I said is what was taught to me by the Ag Extension Services that provide assistance to farmers producing their crops. I do stand by the blueberry stuff. Nitrates are bad for blueberries. Period.

You are probably right about pines and maples. Sorry for over-reaching or over-extrapolating my thought process.

No worries, you are not wrong! Generally speaking, you are absolutely right! There are many arguments to be made against my statements and I believe the true answer lies somewhere in the middle.
I commend and respect you regarding your blueberry operation, and your knowledge carries a heavy weight in my view in the sense that I will not disregard it or call it talking out of a hat. We have a difference in conviction, that's all.

A couple months ago I found a preprint paper that stated that brassica, a family known to have no mycorrhizal connections, does in fact have a fungal commensal community in the wild varieties. It took 20 years of research to figure that out, mostly because nobody ever cared enough; the crops were doing good and there was no need for making them do better.
I have the same view about bonsai sometimes: we can dive into the depth of vapor pressure deficits and how many pascals our barometer reads, and dosing water and solutes exactly right and it would gain us one extra day of growing season. But one more day of warmth in the spring would have the same effect.
However, the disease resistance the fungus in my conifers seems to cause, is amazing. I no longer need to treat for needle cast in inoculated pines, at all. They don't get infected anymore.

I am wrong about the no nitrates for blueberries, very likely at least, but I dream sometimes. And in that dream somebody finds a myc that can resist it, maybe even process it, and provide the blueberries with some extra layers of protection or the ability to use different types of nutrients. I stepped out of bounds with a hard statement more than you did Leo.

Fun fact: my country had an outbreak of Hepatitis C (which can be considered an STD) from frozen blueberries. We test for just about any microorganism out there to make sure food is safe, but viral pathogens from a human source? That's a new one. The jury is still out on how this could have happened, but the manufacturers claim that someone didn't wash their hands. I assume blueberries are washed and dried before they're processed and hep C usually doesn't travel far when exposed to dry air. The take home message here I guess is don't shit in the sink and wash your fruits and vegetables even if they were frozen. Not because of the nitrates though, but because it's difficult to explain to a partner that blueberries were the source of an STD that could lead to liver failure.

 

[pawelo73]

Maybe instead of wooden, use some straw pellets. Once I added some to the soil mix and 2 season later while transplanting, I noticed that the roots of a wild plum almost ate this pieces of the pellets, and it grew very well.

 

[Paradox]

Might work for trees that appreciate a bit more moisture but I would not use it for pines and juniper.

I'd be concerned with it clogging the soil in any case