Rock only soil wont kill my tree?

Hey guys so since im newer to bonsai, the whole rocks being used for soil and no organic material being used for soil is confusing me. I dont understand how the tree can survive without it having some sort of compost? How does the tree survive on only lava rock, pumice, akadama, etc… i would assume the roots would dry up, i have a bag of akadama but i wouldnt want to kill my tree. And is using compost better than using inorganic material? Or vice versa? Thank you guys

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The inorganic mixes are great because roots need oxygen as much as they need water, and they really help to promote oxygen flow. With the inorganic soils, though, you will need to water more often (at least once a day) and be on top of fertilization. That’s the trade off.

That said, some people will use potting soils or add compost or other organics to their soil mix. This generally means the bonsai can be more hands off, but maybe won’t reach that top level of refinement.

If you haven’t watched it yet, the soils video in the archive is a great primer.

https://live.bonsaimirai.com/library/video/soils

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To echo @nmhansen Ryan does say that Mirai checks the trees 3-4 times per day for water needs. He also has shade clothe that he can deploy quickly should the need arise. I think that if you leave a tree in 1:1:1 or a 2:1:1 in a small pot in the sun in 95+ degree weather for 12 hours with no shade or watering, I wouldn’t be surprised if it weren’t happy when you get home.

What we don’t know is how much ultimate refinement do we give up by not using Ryan’s mix and using organic components that buy us flexibility to allow us to do Bonsai within our schedule/other life constraints.

Someone once likened this debate to a professional driver being able to out-race everyone in a Ferrari, but for most people that would be an over-kill and a Toyota will be a perfectly reasonable car. So I think that Ryan’s argument is that if you want to push your Bonsai practice to the highest level, this is what he thinks is best. But I bet you will have perfectly reasonable trees if you use a more water-retentive mix than he does and do most other things roughly right.

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But just using the inorganic material seems like its getting too much oxygen? How are the roots not drying out

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I guess it depends on where you are located. I can tell you from personal experience in the Pacific Northwest, that I will have to water twice a day to keep them hydrated in the heat of summer. Once a day in spring and fall if it doesn’t rain (although sometimes I’m still watering twice a day if a particular tree is really growing strong).

That being said, if you don’t feel like it’ll work for you to go completely inorganic, you can definitely add compost or bark to help keep a little extra moisture around.

I’m fairly new to bonsai too, but have gone headfirst into the Mirai soil mixes (because I’m in the same climate) and haven’t had an issue yet. In fact, a lot of times I’m worried I’m overwatering and keeping some trees too wet.

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One more thing to note, I think it’s important to watch the repotting videos too, to learn about the value of the different soil components. The videos of a second repotting from earlier this year are pretty interesting.

When you first repot a tree out of a nursery pot or field or whatever, there will still be organic soil around the rootball that you shouldn’t be removing. This will leave a fair amount of organic soil in the pot. During the second repotting, you’ll see for yourself the difference in root growth between the organic and inorganic parts.

And above all else, this is why proper watering is so important.

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I live in the northern hemisphere it gets a bit hot here, ill try and see how a mixture of both go for me then ill proceed to see if I’ll make a switch to inorganic material

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Like @nmhansen & @gmishuris says, first repot, leave the center soil intact. You WANT the microbiom to migrate to the new soil with the new root growth.
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1:1:1 @ 1/8-- 1/4-- 1/2" for most bonsai works for me here in hot dry Pacific NW. Decideous - 1 part more pumice , junipers differ… some trees like drier… 100% akadama grows REAL good fine roots… research what your species needs… swamp cypress LIKE seting in a pool…
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Using the Organic fertilizer-- Biogold, Dr Earth or equivilent. Micorrizia, good bacteria… Micronutrients and good microbiom… Now you have fertile, fryable (well draining) soil. YOU control the soil. And watering.

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I live in a hot dry environment and I was worried about using the professional bonsai mix so half my trees are in cactus mix from the store. I now know that the bonsai mix stays plenty moist for at least 24 hours and is more consistent than the cactus mix which often has a dry core even after a heavy soaking. There are several trees that I cannot wait until repotting time to get them out of that substrate.

I just went through a stretch of 100-105 F for about a week so I think this should be fine.

I have one sensitive Brazilian Glory Flower (?) in a very tiny pot and full of roots that will dry out (droop) after about 30 hours. Everything else is fine.

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There’s a nice short blog post on crataegus.com right now about microclimates in the yard. Mid-day shade, protection from wind, and keeping your pots on or close to the ground dramatically increases soil humidity and reduces transpirational demand. I live at 7000’ (really low humidity before the monsoon kicks in) with moderately hot temperatures at this time of the summer, but all my trees are in lava and pumice. Once a day soaking is plenty for my conifers. I put my shohin deciduous in slightly deeper shade this time of year since I can’t water in the middle of the day.

Good luck, and welcome to the fun!

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I also have a soil question. Making my first trip to the nursery this weekend so I prepared a bunch of Akadama, Pumice, Peat Moss, Sphagnum Moss, etc. My plan was to do 1:1:1 akadama:pumice:lava rock…

But - I can’t seem to find any lava rock. Could someone provide 1, 2 or 3 alternatives so I can try and get at least one of them before the weekend?

Thank you!

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No one has mentioned the function of particle size? Soil is so damnably complicated.

The organic component of substrate media holds a high amount of water and typically will have a high cation exchange capacity (CEC) for holding fertilizer. Pumice and akadama both hold a fair amount of water. Akadama and zeolite have high CEC values. Particle size will dictate how much loose water will be held between the particles. If it holds too much water, you get too little oxygen to the roots. If it holds too little, then too much air is flowing and the roots dry out.

To find the specific answers to your needs, begin with local bonsai growers. Then specify the species. Then experiment on trees that you’re comfortable with killing.

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Amazon has black lava 3/8

Not cheap but is a color that does not offend the eye.
:thinking:

This is a good size that I have used. I think 3/8 is too big. It is also way cheaper than buying it in small sizes (e.g. quarts) unless you just have 1-3 trees.

I buy it by the pallet. Looking at these prices, I’ve been selling cheap.

This is the inside of my greenhouse because I don’t have anywhere else to store it.

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Do you have a website?

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I have a crappy one. :slight_smile:

I still don’t ship these. I haven’t been able to find a bag that’ll conform to the shape of a Large Flat Rate USPS box. Those boxes are just under 1/2 cubic foot (just over 3 gallons). As soon as I do, I’ll have to start shipping this stuff out.

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Jump to 1:23 in this stream. Ryan talks about adjusting your soil to your lifestyle. Ppl have added pine bark to their mixes and have achieved good results.

https://live.bonsaimirai.com/library/video/hinoki-aesthetics

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This is how I’ve been doing it over the corse of the last year I’ve started on this path with all my repotting and don’t forget fertilizer is good but the real food is the photosynthesis my plants aren’t as explosive in growth but so far they’ve all survived being repotted in 1.1.1. I also check water three times during the day and I use the spaghnum as top dressing so I can monitor humidity around the soil

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In 2014 on my first visit to Ryan I asked him what to use for my old Ponderosas. He said Pumice. DUH! So I say brilliantly how do they get enough water to survive? He explained briefly how Pumice is just like a sponge in rock form. Full of little holes and passages that hold H2O and fertilizer as well as giving lots of O2. I use 100% for my conifers and about 60-70% for deciduous and sift for size using 1/8-3/16 for small trees, 3/16-1/4 for medium ones and 3/16-3/8 for my big ones. I use no krapadama and very little lava as it holds very little H2O. I have no tiny or shohin trees except as little trees growing bigger and all these have some organics. Even in our 100 degree weather trees are not shaded and only some of them get watered 2 times a day, Amazing how little rocks work but they do. I just took Ryans word on faith.

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