ingredients of bonsai grittier mixture

mrtulinJanuary 7, 2011

Not having the ingredients for gritty mixture close by, I bought bonsai soil from a very reputable bonsai retailer. I asked its composition and it is


1/3 potting soil which is comprised of metro 5/10; pine bark fines and vermiculite


1/3 coarse sand (?) I actually didn't write down what product was coarse, but I'm guessing sand.

No other additives.

What do I need to add to it.

I'm using weak MG

I am repotting houseplants in it: begonias, amaryllis, and going to get to cyclamens.

I'm interested in your responses.

It was ridiculously expensive so I really want to make 1-1-1 "from scratch" If the plants do well, they'll just stay in the bonsai mix. I'll concentrate on getting the 5-1-1 mix for my outdoor pots.

Time to reread Al's advice on fertilizing.


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Hi, Marie!

When I first read Al's writings and decided I wanted to try a more aerated, grittier soil for myself, I ended up with a small bag of bonsai medium as you did. This was before I began really looking around for the individual ingredients.

The bonsai soil was outrageously expensive at around $8 for a very small bag... and by very small, I mean only enough to re-pot one or two of my bulbs, if that.

The ingredients were listed on the bag's label, and it consisted of fir bark, granite chips, turface, sand, and something else... I can't recall what the other ingredient was... some kind of lava chip, I think. It originated from a bonsai shop on the east coast. They bag it and sell it to nurseries across the country, apparently.

The particles are a bit smaller than the Gritty Mix, but it's a good place to start. For me, it was the motivator to begin searching for ingredients to mix it, myself. I couldn't afford to buy multiple bags of the bonsai medium, and I would need quite a few to re-pot my bulb collection. Besides, the nursery only ordered about 4 bags at a time... I asked them.

I began looking in the gardening section of every store I went to, searching for pine bark or fir bark pieces. The large chunks I found were way too big. None of the bagged mulches were what I was looking for. I couldn't find any of the soil conditioners or aquatic soils that were recommended... and the fir bark is what I would consider the main ingredient! They all are necessary, but without the fir bark, I might as well give up the ship.

Someone suggested Repti-Bark fir bark bedding for reptiles, available at PetSmart or any other pet store that carries reptiles. I looked into it, and it's exactly what I want!

We are rural, so we have farm oriented stores in the area. It was easy to locate the granite chips. It's bagged poultry grit in the form of 100% granite chips. If a person doesn't have access to to farm stores, a pet store that sells aquarium gravels might have a size of stone we look for.

Well, there's plenty written here in the forum on locating the various ingredients...

You wanted to know what someone else might mix with the bonsai mix... I tried all manner of concoctions when I first began. I even went back and reread Al's article a few times, just so I had a better feel for how and why I was doing this. For me, every key is located in that first article.

It's extremely helpful if all the medium particles are approximately the same size. I found that the bonsai soil was just a little bit too fine in nature. The chips and particles were too tiny. Too large isn't good, either... which is why the pine mulch products I looked at wouldn't work.

I ended up using the Repti-Bark fir bark, granite chips, larger sized perlite, and turface. For me, this mixture is a good balance. It retains just enough moisture to keep some water vapor around the roots for about 2-3 days in my environment.

The bulbs that I originally potted into the bonsai medium have been in it now for about 2 years... it'll be time to re-pot them when spring gets here.

Quite honestly, Marie, I think you'll find that the bonsai soil is just a bit too fine for our uses... but it'll give you a good idea of what we're going after, the results we hope to attain. Learning how to water it will be an experience, too. I suggest using the wooden skewer method of testing for moisture around the rootball.

A friend of mine just re-potted some of his Amaryllis bulbs, and he mentioned to me that he found roots growing upward toward the soil surface, toward the pot sides, and generally all concentrated within the upper portion of the soil he uses. He uses a heavy bagged mix. I explained to him that those roots were starved for oxygen, and were literally drowning in the heavy soil he uses. They were growing toward oxygen sources.

What he found under the soil in his pots is exactly what I found, and what prompted me to learn more about the science of container growing. I had the added issue of rotting bulbs from too much moisture.

I find fertilizing to be very easy... I use a very weak solution of 12-4-8 liquid plant fertilizer, and I add a pinch of micro-nutrients. I use this to water almost every time water is needed, and I flush the pots with clear water every so often to avoid salt build-up. My bulbs and other plants love having a continuous food supply.

If you add your bonsai mix to anything that is finer/smaller particled in nature, you'll be defeating the purpose... and the smaller particles will fill in and settle around the larger particles, thus eliminating the aeration you're trying to give it.

I don't know that I've answered your questions adequately, but maybe telling the story of what I did will help you in some way... rereading Al's articles a few times, and referring to them as references, helped me a lot.

Never fear, though... you've got plenty of help here, in all the "gritty mix gardeners" offering their wisdom and methods and bits of advice. It's a great bunch... you couldn't ask for nicer, more patient helpers! :-)

I wish you the best of luck in your growing endeavors! :-)

    Bookmark   January 8, 2011 at 9:37AM
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Thanks, JoJo, for taking the time to go over your own experience. As I wrote and you noted, I knew it wasn't optimal but at least it got me started re-potting.
I have done the reading, thought not re-read but by the time you read everyone's post it is impossible not to get the picture.
Thanks again,

    Bookmark   January 8, 2011 at 10:23AM
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JoJo and I have such similar names... I'm Jodi, and she's JoJo. We figure we're sisters separated at birth! ;-)

I think the bottom line is that it will take a little while for you to line up the ingredients you'll eventually stick with... I know it did for me... so, in the meantime, playing with the bonsai medium will give you a better idea of the whole concept, etc... and it will fire up your imagination, get you thinking about those obscure places you might find the actual ingredients you'll end up using.

I have a very poor memory, so rereading the articles Al wrote helped to drum the information into my brain. It's probably not a necessary thing for other people, but if I don't read something more than once, I find I forget or miss important little tidbits of information.

To make it go further, I originally mixed the little bag of bonsai mix with some perlite. I also mixed a little bonsai medium with the regular bagged soil, but found that to be too moisture retentive... not what I was looking for.

For me, the intent is to find a retention of moisture that works for the particular plant type, while allowing for fast drainage and good oxygen/gas exchange.

Unless you have all the necessary ingredients within easy local access, it's going to take a little time and experimentation before you and your plants are happy.

I just kept reading, and searching for the right ingredients every time I went to town.

Don't worry... it'll all come together for you. :-)

    Bookmark   January 8, 2011 at 11:35AM
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tapla (mid-MI z5b-6a)

I agree with all Jodi said, Marie. Hoffman's makes a bonsai soil that they package and sell. It's very expensive - probably more than $10/gallon, and I would actually use the 5:1:1 mix before I would use it because it's much too water retentive.

I've been practicing bonsai for more than 20 years, so when someone starts talking about potting soil and sand in their bonsai soils, I'm immediately thinking 'reduced aeration and excessive water-retention, the two primary considerations we want to be certain are not an issue in our bonsai soils. Bonsai trees are just trees - trees are just plants - they like the same things that other plants like.

It's kind of important that you understand that I'm saying this from an analytical perspective. I'm not trying to talk you into this or that soil: When you start with a soil that has a large fraction of small particles, you can't amend it effectively by adding larger particles. I usually use the example of pudding - how much perlite do you need to add to pudding to get it to drain well. 'LOTS' is the answer. The perlite needs to me well over half of the total volume. 60-70% is about right. The same is true of heavy peat soils. Adding perlite really doesn't improve drainage or aeration for a significant period. The small particles of peat quickly settle around the particles of perlite, and it's as if they weren't even there. All they do is take up space that otherwise might have been occupied by water; so perlite's primary benefit to soils, unless it is present in large fractions, is simply to take up space and reduce the total volume of water a soil can hold.


    Bookmark   January 8, 2011 at 11:35AM
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