Cinder as part of Bonsai Soil

Most of us Bonsaists use different types of bonsai soil. I have been party to debates on Organic versus Inorganic and the types. However my query is very specifically on one component of the bonsai soil - namely cinder.

I am planning to use Cinder for the first time next spring when I repot. I would be using cinder as a sand substitute. The reason I am considering cinder is that it is rough. I was told that rough/coarse sand is better than rounded granular sand as this helps in developing fine feeder roots. As I have very limited access to the rough variety of sand, I am planning to use crushed cinder of around 1-5 mm size along with my other soil components like organic compost, leaf mould and soil.

I was wondering if someone has already done so. And if so what has been the result. I would also want to know if cinder, chemically is harmful to plants in any way. Pls do share your views.

Thanks in advance.
Regards
Ravi

I looked at the Internet and found information on volcanic cinders, but not much on coal cinders.

I did find that they have a fairly high pH, as I suspected. Probably in the range of 8.0 and up, probably depending upon the original sulpher content of the coal. There could be other trace compounds in the cinders also that might preclude using the cinders with food crops or around people. I would wash them and avoid the dust and/or wear breathing protection.

I think I might try the cinders with a few plants that I didn't mind killing first.

There was a discussion on this topic some years ago on the old IBC. Sand or gravel is used in bonsai soil to open up pore spaces so the roots will have more air and better drainage. Think about it. The particle shape that provides the most space is a ball bearing. Use sand or gravel with rounded contours, like aquarium gravel, if it is available. The idea that rough particles promote root division is a pure myth. Root division is initiated on a molecular level, and is influenced by the total environment rather than the particle shape.
Iris

Well, as far as I remember, cinders are used for Pot - grown Rose by professional Rose exhibitors with good result in Bengal-India.Rose does love a bit acidic substrate. Sulpher if present in cinder to my mind it would add a bit of acidity to the substrate.

I have never been in India, but around here the practice of growing potted roses is completely different from bonsai. You can try it, but proceed with caution.
Iris

Billy,

Thanks for the bit on Sulfur and the pH part. Shall keep that in mind. Like you said, I'd try the cinder mix on hardy plants (I'd not like to kill any of my plants ). Ficus would be a good bet. Shall keep you posted mid next year on the progress.

Soumya

Thanks for sharing the info. What is good for roses should be ok for Bonsai. I am encouraged and shall try the cinder experiment.


Iris,
Thanks for your comments.

Regards
Ravi

I know some artists use it for satsuki, especially when they have no rainwater in countrys with hard tabwater.

Peter

Ravi,

before using cinders from iron or scrap metal processing, check for radiation and metal toxicity [ see Billy's comments as very serious ] DO NOT not breathe the dust!!!!

As to Ms. Iris's comment, ball bearings, makes sense, which is why you sift for a given average size. If you add in big and small particles, you are making a concrete mix and the clay / compost / manure mix will bind hard when dry. On our side this is how clay based floors [ leepay ] are done with cow droppings [ go-baahar ]

Construction sand is crushed and can be sifted to get the ball bearing effect.
No brick factories near you [ with x miles ] ?

I have kept all of my inorganic ingredients sharp, because of the root separation bit, but if Ms. Iris says no way, it is most likely it is so.
However, my soil also has the ball bearing factor.

My mix is freely draining, even unto the end, and I have trees that are repotted every 3 to 5 years.
See you later.
Khaimraj

Khaimraj Seepersad wrote:
I have kept all of my inorganic ingredients sharp, because of the root separation bit, but if Ms. Iris says no way, it is most likely it is so.
Khaimraj

This comment was originally posted by a professional soil scientist.
Iris

My biggest concern about using cinders would involve the original source of material burned, the type of fuel used and any other potential contaminant.

If you can't be sure of the chemical composition of potentially leachable materials, you cannot ensure that cinders won't be toxic to your plants.

Jay

Khaimraj,
Thanks for the comments. I would take your advice and that of Billy seriously. Besides not breathing in the cider powder, I also plan to wash it clean. Construction sand is indeed available, except that it is not sifted. Infact when being used for construction it is the finer ones that are used and the thicker 2-5 mm ones are often discarded. The challenge lies in raiding construction sites which can be quiet tedious if not outright embarrassing. The option of getting the sand and trying to sift leaves the challenge of discarding the fine sub 1mm sand which can be over 60%. It is because of these reasons that cinder appealed to me as an alternative. Keeping my fingers crossed for now.

For me repotting is once every two years if not annually depending on the tree. Ficus' get pot bound very quickly as do schffleras.


Peter
I was also encouraged to see the suitability of cinder for Azaleas. I have made the mistake of getting a single azalea plant despite being in the tropics. I pity the poor tree as it is struggling to survive after giving me 2-3 beautiful flowers. Cinder with its acidic base might be just the solution. Keeping my fingers crossed.



Jay
Thanks for the words of caution. Shall take note and do the needful.

Regards
Ravi

bonsaisr wrote:The particle shape that provides the most space is a ball bearing. Use sand or gravel with rounded contours, like aquarium gravel, if it is available.
Iris

Though I agree with the rest of you post about root division, I don't agree with this particular statement. Maximum porosity of a material made of spheres of same diameter is easily calculated : 4/3*Pi*R³/8R³ , that is 0.52. And this is the maximum porosity, calculated with the hypothesis that all the spheres will have their centers separated by 2R. In reality, they're not and the porosity shrinks to about 1/3 if I remember well.
According to my measures , crushed rock 's porosity is around 0.4-0.45; pumice 0.55-0.6 and lava rock around 0.65

Alain,

does your knowledge also extend into the organic part of the soil mixes used in Bonsai.

I was reading at an Indian Bonsai site and saw a recommendation for red clay / manure / sand. I am in the West Indies [ Caribbean ] and that blend would be considered a death mix. Our rainfall is at least 5 feet [ 153 cm ] yearly and much higher.

I also wonder what happens if the core, the area around the trunk, is filled with such a mix, if after say 10 years of growing, the heaviness of the decayed soil, would slowly kill the fine branches of the bonsai ?

The Japanese images from the late 50's to 70's show the digging out of clay type soil mixes around mature bonsai.

I am asking al of this on Ravi's behalf.

Does anyone know of any other porous rock type that he might find around his area in India?
I spoke to someone on the Cinder from metal refining and the cinder also contains fluxes, that can dissolve with time and poison his trees. I also not keen on his having to work with this material, as it is considered highly toxic on our side and even using it as cheap road fill is frowned on.
Stay Well.
Khaimraj

Hi Alain,

Thanks for the maths. Math Rules!!! I could'nt agree with you more. You've added a math dimension to my belief that porous rock has its advantages. Thanks a ton.

Khaimraj,

Thanks for the request on my behalf. I second it Coming to the cinder I thought I was referring to burnt coke which is distinct from metal refining cinder. A little confused. Pls clarify.

Coming to the soil mix what you've read is perfectly correct and it is what is mostly used in India. There are minor variations but the vast majority IMHO use one part each of Red Clay, Organic Manure and Sand. I have been doing so with good results. Trying to up the content of Sand (or sand substitutes like cinder) as the organic manure compacts the soil and the so called Red Clay is too fine that it'd be shunned in the rest of the world. We still use Red Clay as it retains moisture better considering our dry conditions with the exception of monsoons between June and Sept. One of the reasons why I need to repot my Bonsai often is that in about a year this mix that we use compacts to the point of choking the roots and this clearly shows, as the leaves become yellowish and have this very unhealthy look. Immediately on changing the soil the leaves return back to the normal healthy green and the cycle repeats every 1-2 years. Guess that puts things in perspective.

BTW pearlite is also available in India but its extremely high price makes it unviable on a large scale.

Regards
Ravi

Ravi,

http://www.conrad-errg.ca/Technical%20Committees/Coke%20Toxicology.aspx

We had a woman potter down here who loved to mix clay and manganese dioxide, gave nice dark bodies, she died from manganese poisoning. It is never good to mess with industrial materials unless you have read the msds.
[ Nickel and it's compounds are also not cool to play with.]

I am also not sure what high doses of Sulphur compounds do to trees. On this side near the natural Pitch lake near La Brea [ Trinidad W.I not the U.S.] banana plants do well.

Perlite can be hell, visually, with the floating nuisance.

I do pottery and make my own glazes, I have to have an awareness of oxide toxicity.[ see Patty's Industrial or the Pharmacopoeia ]

We are spoilt on this side, island is about 50 x 50 miles [ km ?] and the size of say London, but silica based gravel deposits are easily obtained in the north, and brick factories have broken brick piles that you can sift through, as well as underground naturally fired clay. Perhaps you need to see a geologist or find a brick depot at the hardwares ?
You should have hollow clay blocks for building?

Yes, I thought the red clay would perform like our hardened yellow clay stones [ they melt within a year of use ] A real pain if you reach the 10 year and needing 3 to 5 years to repot. Worse if the trees are 2 feet + [ 61 cm ].

Just take your time and see what you are exposing yourself to. On our side Indians are very prone to diabetes and most go from type 2 to type 1 without having checkups. It is because they claim to be vegetarians, but actually they hate vegetables and are really starcharians with high oil consumption. In fact the only vegetables they like are those with sugar and oil [ and lots of sweet fruit / tamarind sauce etc.] Playing in manure / compost will expose you to many situations, and diabetes weakens the body's defence mechanisms. Do like the Japanese - wear gloves.
Stay Healthy.
Khaimraj

* Also be aware of Silica - cryptocrystalline forms.

Khaimraj,

A little overwhelmed but I understand what you are saying. Thanks I shall be careful..

Ravi