Category Archives: Growing

Bonsai Soils and their usage

Bonsai soil is a topic that may seem basic, but it can be quite a deep subject. No pun intended.

Quite obviously, bonsai soil is the medium by which the bonsai is provided water, fertilizer and oxygen. In order to do this most effectively, however, it requires varying types and sizes of soils. A bonsai tree requires these different particle sizes and types of soil because it helps them to grow better and emulates the soil the large cousins of the bonsai grow in.

Soil Science 101

Imagine a cross section of the Earth like you see in science books. At the very top, the surface of our planet, there are two levels: bedrock and sediment.

Bedrock is the farthest you can dig with a shovel before you need drills to pierce the rock. On top of that is the sediment layer. This layer is really not that deep comparatively. In some creeks, it’s a mere 2 – 3 feet down. Typically, however, the depth of sediment is 18 – 60 feet deep.

As we look at this layer of sediment, no matter how deep it is, we find that it is made up of various layers of material that increase in size as you go deeper.

On the top layer of sediment, you find silt, which is like powder. This silt most often has organic matter mixed in with it. Going deeper, you find rocks that were once pieces of bedrock. On the top most layers these rocks are pea gravel sized. Then they increase to gravel, then stones, cobbles, then at the very bottom, boulders.

This layering effect is a natural byproduct of gravity. The resettling is a natural result that occurs over thousands of years because the Earth is spinning and going around the sun and water frequently saturates the sediment.

What we find when we look at the large trees is that the root zone is primarily in the mid level of the sediment. This level quite frequently also retains the most moisture as well.

Every time it rains, the water leaches into the soil. As the water percolates down, it draws oxygen into spaces and gaps between the soil particles. The water is held the longest in the mid layer because the top layer is warmed by the sun and blown by the wind, and the bottom layer has mostly larger rocks which don’t hold a lot of water.

Types of Bonsai Soil
Our goal when choosing bonsai soil is to create the same type of environment that the tree would naturally live in out in the wild.

In order to do this, we will need to duplicate the various layers in nature in the bonsai pot. We would just do it on a smaller scale. The top layer particles would be around 1/8 of an inch, the mid soil layer would be ¼ inch sized particles and the bottom layer would be ½ inch and larger pieces.

We can use several different types of soil. Namely, we can use akadama, kanuma, haydite, pumice, grit, gravel, pine bark, peat moss, calcined clay, river sand, top dressings and zeolite.

Basically, these materials comprise types that retain water, types that don’t, and types that do both –they hold some water and they fluff, and aerate the soil.


Akadama is the best known, all purpose bonsai soil. The name means “Red ball soil.” It is the volcanic clay that Japan is made of. It holds water very well, but due to larger sized particles, leaves plenty of room for oxygen to get to the roots. Akadama will break down over time into a silt type sediment.

Calcined Clay

Calcined clay is ground up brick. The brick making process ensures the product will never break down. Calcined clay is sometimes preferable to sand because it has larger pieces and screening gives you several different sizes. Calcined clay will hold water somewhat, but it’s purpose is to fluff the soil and make it more porous.

Haydite / Expanded Shale

Haydite, also known as expanded shale, has undergone a firing process that forces it to explode from the inside. This makes it hold some water, yet it mostly makes the soil porous. It can be screened into several different sizes.


Pumice is a white volcanic rock which is ideal for bonsai soil mixtures. It holds some water, but chiefly aerates the soil making it more porous.


Grit is larger pieces of sand that are sharp. Grit opens up the soil and does not hold water.


Kanuma is Japanese soil, like Akadama, but it is slightly acidic. It is used mainly for Azaleas, Camellias, Gardenias and other acid loving Bonsai. Kanuma holds water well and comes in various sizes.

Peat Moss

Peat moss is an organic sphagnum moss that comes from the peat bogs of Canada. This product holds moisture for a long time. This product typically comes in long fibers, but can be broken down into a small powdery material.

Pine Bark Chips

Pine bark is an organic soil amendment that is about 50/50% dual duty. It holds moisture, though not as much as sphagnum moss, and it fluffs the soil, though not as much as haydite, calcined clay, river sands or grit. Since it is organic, it will break down over time.

River Sands

A type of grit that is excellent at opening up the soil to oxygen. It ranges in size from 1/8 inch to ¼ inch, so is best for top and mid layers.

Top Dressings

Mostly used for decorative purposes, top dressings are sands or stones and do not typically have any purpose in bonsai soil other than a purely aesthetic purpose.


Zeolite is similar to Akadama and Kanuma. It is quarried in Japan, and retains moisture and can be screened into multiple sizes for use. Zeolite is more akin to Akadama than Kanuma however, because Zeolite is PH neutral as is Akadama.

Putting the Soil To Use

Some species of plants require a soil that retains more water and others enjoy soils that are more porous and dry. This means that you can use the various soil materials to create specific versions of soil for specific types of plants and specific climates.

The mixtures of soils can vary from heavy moisture retaining, to arid soils. Since Akadama or Zeolite are excellent bases for soil mixes, I suggest using various sizes of these and mixing in percentages of other material depending upon layer and species. Note: If your plant is acid loving, substitute Kanuma for Akadama or Zeolite.

For example, Maples and Beeches thrive in 100% Akadama that has been screened by size. Junipers like 50/50% mixes of Akadama to calcined clay, haydite/expanded shale or grit. Most every other tree falls in between these mixtures.

While it might sound more complicated, most trees, if not all, would thrive using the layered approach found in nature. This means that the soil from bottom to top is made up of several different materials in differing sizes.

Starting with the bottom layer as if potting a plant, add large pieces of akadama, calcined clay, pumice and haydite in pieces ½ inch or larger to the pot. On top of this layer add in ¼ pieces of Akadama, pumice, pine bark chips, and river sand. It is into this layer that you will plant the tree. On top of this, the top layer would consist of 1/8 inch pieces of akadama, pine bark chips, and pumice. To top it all off, you could then apply a top dressing of sand which complements the pot and the tree.

Hopefully you now see that there is a science to soil which takes it out of the realm of mere dirt. As you purchase different materials and spend some quality time with your bonsai, you will start to see how all of these materials can work together for you. Every mixture can be tweaked depending upon the climate your plants live in. If it’s extremely rainy, windy, cloudy, or sunny throughout the growing season, you may need to tweak the soil depending. If you live in Arizona and want to grow bonsai, you are probably going to have to add peat moss to your soil. If you live in Seattle, you are probably going to want to add more pumice, calcined clay or grit.

Back to Basics – Bonsai Growing Tips

Bonsai trees are sometimes difficult to grow for some people. Often times, someone gets a bonsai tree as a gift from a person who does not really know a lot about them either. While there is nothing wrong with this, it makes it all the more imperative that the person who has received this gift do some research on the plant. With some knowledge about your tree, you can grow a bonsai tree on your own with no problems. That said, Bonsai trees will take a certain amount of work that some other plants will not. Many people who receive these trees as gifts simply put them next to a window to get some sunlight and do not bother with them afterwards, except to water them once a week or so. A bonsai tree in this situation will die quickly. The truth is, when taken care of properly, a bonsai tree can live for hundreds of years or more. Seriously!

The first thing you must do to take care of your bonsai tree is to find out what species it is. This is so important because every species has different needs. Finding out what species your tree is can sometimes be a daunting task because there are hundreds of species of bonsai trees. But finding the general name of the species will suffice because then you will know the type of environment it prefers to live in. After you find out what species your bonsai is, you will more than likely be sitting it outdoors unless it is a species of tropical bonsai, which will need special care. Of course, if you live in a tropical climate, it would be fine to sit your tropical bonsai outdoors. Bonsai trees can usually not survive indoors for a number of reasons such as lack of humidity and light.

The next important step is learning how to water your bonsai properly. Watering your plant properly is crucial to its survival. Unfortunately, this is one of the most difficult parts of bonsai cultivation. Every species will need a different quantity of water. Too much or too little could quickly kill your bonsai tree. Bonsai trees are usually in a smaller pot, which will have a smaller amount of pourous soil. Bonsai should have a rocky or pourous soil by the way. Not the loamy soil gardeners usually prefer. This smaller amount of soil will cause the bonsai tree to dry out quicker or suffer from other temperature fluctuations very easily. Using the right size pot is also important to your plant’s health because the roots of the tree dictate the pot size. Most bonsai trees will have to be watered every morning and evening in the summertime. I’ve heard that watering the plant during summer mornings will adversely affect the tree. I’ve also heard the same thing about watering in the evening. A good rule of thumb is to check a couple times a day if your tree is thirsty. If it is, give it some water. My thinking is that it rains whenever it rains and I don’t see a lot of trees with fungal growth and rot in the wild.

How To: Repotting the Japanese Black Pine

Repotting the Japanese Black Pine is actually no different than any other tree repot in the sense that it is something that is needed and that the right timing and soil are used to get the tree to respond to its pot acclimation in a healthy and positive way throughout the year. It has recently been noted by those who have been working with Japanese Black Pine for a good many years, that it helps very much to repot on a yearly basis with these trees or at least every other year rather than going by the old school method of waiting sometimes up to five years for older trees.

In my recent purchase of a few Japanese Black Pine that had probably not been repotted in a few years, the soil had hardened to almost brick like consistency and the tree, even though it still looked good, was weakened considerably in that it wasn’t back budding the way it should.

Japanese Black Pine should always be kept as strong as possible because they have to go through a lot of stress during the decandeling and needle pulling at one of the most stressful times of the year, mid summer. The repot will encourage new finer feeder roots and together with the new fast draining soil, will give it a boost just before the new candles begin to open in the spring.

Repotting here in the U.S. and especially here in Texas is right around mid December to early Feburary and usually no later. Other northern states might be able to wait a bit later. As with any repot, keep an eye on overnight temps and see to it that you take every precaution to keep the repotted tree from freezing temps as this will most likely hurt the new fine root system that will just be developing.
In this first pic you can see that there was plenty of soil for this tree, and most of it pretty hard so that when watering, the water had a hard time draining through it so that it actually sat on top of the soil for a while and not really soaking through the entire root structure.

You’ll notice the root rake that was used and how much was needed to take off of the old compacted soil.

You don’t have to be afraid to scrape off dilligently if the root ball is really compact because it needs to come off one way or the other. You may need to scrape a small layer off the top also. Now when I say dilligently, I don’t mean to start tearing roots without any concern, but being too gentle might not get you where you need to be either. If you have been doing repotting of trees for a number of years you’ll already have the feel for it. If you haven’t, just use a little caution and common sense toward this aspect of bonsai culture and you’ll be alright.

In this next pic you can see how much root I had to remove (outside the red square box) in order to give the root system plenty of room for new growth.

It’s a good idea also to have your pot ready to go with anchoring wires and your prepared soil nearby.

A good soil mixture for JBP is:

  1. 1 part akadama
  2. 1 part lava
  3. 1 part pumice

Be sure to filter out the fine particles from each with your soil sieves.

After the tree has been placed exactly where it needs to in the pot, begin filling the pot with your prepared soil mix. while doing this, use either a chopstick or as I do, your finger to make sure the soil is filling up all the spaces around the root ball. I like to use my finger because I can tell for sure what’s going on in there and I believe I can get the soil to settle in better this way.

Remember the first tree above with the compact soil, well here it is about six or seven weeks later with its new candles all a glow. By the summer decandeling she was ready and waiting.

And how about the other one where I had to take quite a bit of root off in order for her to breathe in that narrow semi cascade container. Here she is with her candles all grown out and begging to be decandeled. Notice how healthy she looks all due to a good repot and a good soil change.

Here’s a recent picture of the same tree after its fall work.

A word of caution if your Japanese Black Pine is an older specimen with rough flaking bark such as the Mikawa cultivar as seen here.

Do not grasp the tree at the base where you will stand a good chance of tearing off the delicate bark, but rather hold the tree farther up the trunk by the branches. This will insure that your trunk at the base will continue to look old and aged without any tear out.

Well I hope this small article will be of some benefit to those who may be doing their first Japanese Black Pine repot this year. By the time you read this article it will almost be time to repot for some, or at least time to get those new pots and soil mix ready for the necessary task that lies ahead.

Would You Consider A Buttonwood Bonsai?

For those who like to have their cake and eat it too, and by this I mean, if you like doing bonsai, and like to have a tree or two indoors, have you considered a buttonwood?

Anyone who has been into bonsai for a while, knows that most of your stock, especially the junipers, are outdoor trees. Most discovered this after their first purchase went belly up after a few short weeks sitting on the coffee table.

There are trees that can be brought indoors, but even those can’t be subjected to low light positioning while inside. Some will do very good facing a southern window in winter months, while some will need high lighting such as fluorescent lights to meet their needs. You should also consider that even these trees should get some Spring and Summertime help by being outdoors for a good bit of the time. You also have to consider pest problems with trees that are indoors, especially when first introducing them to this environment, either for the first time, or when bringing them in for the winter months.

If you do decide to do some indoor bonsai, then tropical type trees are your best bet, and to me, one of the best to use is a buttonwood. Why? If you’ve ever seen a buttonwood bonsai in a show or in someone’s collection, the first thing you’ll probably notice is the beautiful driftwood on this tree. After it is lime sulphur ed and the wood takes on that nice white look, it is every bit comparable to many junipers that have the same thing.

It is also a tree that responds very well to being in a small container and used for bonsai.

Let me show you what I mean with a few of mine.

The first one below was purchased from a vendor at a local bonsai show. It was the last of the last as you can see from this picture.

It is one of those trees that you have to look far down the road to see its future, and that’s what I did. After finding a new pot to do the training in, repositioning the tree and waiting for new growth was all that was necessary.

It didn’t take long at all before my buttonwood was ready for a new pot and ready to be shown.

As for the driftwood on this one, the whole tree is practically one big piece of driftwood, with a small lifeline on the very left side of the tree. Just for the record, I didn’t use any lime sulphur on this one. I decided from the start, that I would let it whiten up naturally, which I believe it did a beautiful job of also.

The next one was also purchased at a bonsai show, in fact from the same person as the previous one, only a few years apart. Notice how bad the leaves look on this one at purchase. I was kind of skeptical at first, but was very optimistic that I could make this tree not only look healthy, but stay healthy also. Plus I had a vision for this tree in the way I would style it.

Believe it or not, this is only one months training. Look at the leaves now, and also my plans for the way I intend to style the tree.

Now check this out. In only two months after purchase, look at the incredible difference from the first picture as compared to this one. Look at the amount of new growth I got in that short period of time. And whatever happened to all those nasty looking leaves?

Here is the tree now after one years training. Looks very healthy wouldn’t you agree?

One thing to remember when doing indoor tropical bonsai, is that once the outdoor nighttime temps stay at or above 60 degrees, it’s time to take them outdoors for the rest of the summer. Never let your buttonwood stay out with temps in the 40 degree range.

Some might make it, but most probably won’t.

As for repotting them, only do this in mid summer when the temps are guaranteed to stay high for a while.

As for bringing them in at the start of the Fall, again keep an eye on the forecast, and when you are sure they will be staying in for the rest of the winter months, give them a shot of insect repellent to ward of those buggers before they even get a chance to do their damage.

From then on, keep an eye on the dryness of the soil, and water only when needed.

Many people also use humidity trays and whatnot. For me all that is necessary is something to catch the drained out water from the drainage holes. You might need to experiment if this is your first time doing indoor bonsai.

As for acquiring a buttonwood tree, check the online bonsai outlets to see who’s selling them. Hopefully you can find a decent one at a decent price.

Good luck with your buttonwood, and I hope you have as much fun with yours as I do with mine.

Revisiting an Old Friend: Winter Maintenance On An Elm Group

Last August my monthly article consisted of a restyle on a japanese nire elm group that was headed for the dumpster unless something drastic happened to its overall appearence. Well I believe that after fourteen years together, I should maybe give these guys a second chance, and that’s exactly what I did, by restyling the group into something that was more pleasing to the eye. A couple of the last few pictures in the article were something like you see below.

Well six months have passed, and it’s time to do a little maintenence work, or these little guys will be right back where I don’t want them to be, another bush in a pot so to speak. Looking at the picture below, you can see that that’s just about where it’s heading. This is and early Fall picture, and most people especially beginners, would probably see nothing wrong with the way it looks here. I think the picture pretty much shows that it’s a healthy tree.

But hiding under all that foliage is this:

Not a pretty sight is it? Of course there was a reason for allowing it to get to this point, because I had to build branch structure. But now it’s time to work on that aspect. I guess the point I’m trying to make, is make sure you have a vision for every tree you own, and follow up on it. As I just mentioned, many beginners would probably be content with the way it looked with the foliage on it, and just let it keep growing as it is. But I’m hoping if your a beginner, you will see past that and be looking at the finer aspect of bonsai, the part they call “ramification”. Anyone can grow a bush in a pot, but you will put your own signature on your work when you begin to learn the art of ramification on your trees. Once again that will only happen when you develop branch structure, and have something to work with.

So the first thing that needs to be done on this group, is to take off wire that was applied last year and might be starting to grow into the branches. The picture below shows one branch where the wire is almost at that point and needs to be removed.

After spending some time removing branches that don’t need to be there, I wired up those that would be the main focus of the style I was after. I don’t seldom use copper wire on deciduous trees unless the bend is rather abrupt and needs to be held stronger. Usually anodized aluminum wire will work. But I used copper wire on this one for the reasons stated above. You’ll probably notice from the picture below that the wire has ben put on tight so as to hold the branch in the intended shape. I will have to keep a constant eye on these so as to eliminate any wire growing into the branches.

So this is what the group looks like now with just the look I’m aiming for. I’m sure you can tell there are areas that will need to be filled in, but the basic shape is there, and it will be up to me each year at this time to continue the ramification in whatever manner it need be.

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