How to Mix Your Own Bonsai Soil

Bonsai soil comprised of various gritty material.
Bonsai soil comprised of various gritty material. | Source

Introduction to Soil

Bonsai is a hobby that anyone can enjoy. It’s often a hobby people pick up to get in touch with nature if not themselves. As discussed in my Beginner’s Guide to Bonsai, anyone can bonsai by meeting a few conditions. Anyone new to bonsai or to any hobby tends to have many questions; however, quite often, the new hobbyist asks all the questions but the really important ones. How much wire do I need to buy? How much water is too much? What kind of style is most attractive for every tree? Can I bring the tree inside to display indefinitely? How fast will this grow? I need to make sure this tree grows super quick, what can I do to make this tree grow senselessly?! Passion for a new hobby can be like falling in love and it’s easy to let a spark grow into a flame and then into an inferno. It’s important to know that with any new hobby, the hobbyist should be open to suggestion and do what’s logical and proceed with caution and reason. We often overlook the very obvious things even when doing tasks we do every day. Why I stress this asking the right and important questions is because I was one of those who overlooked such obvious issues and didn’t ask the important questions. I’d like to rectify my sin and pass on to new hobbyists the importance of starting from the ground up, literally!

What’s so dang important? In my opinion....Soil. That’s the most important aspect to bonsai and often we disregard it because we perceive a tree as a tree and soil is soil; therefore, anything should work. Soil is more than just digging up a clump of dirt in the yard and putting it into a pot and say: “we’re done with step 1, let’s move on.” Part of being in the bonsai hobby is being a little bit of everything: i.e. horticulturist, geologist, artist, and ect. What one is trying to do is to replicate nature and nature has been at this game for a long time so it’s safe to say “imitation is the sincerest form of flattery.”

Different components of a standard bonsai mix.
Different components of a standard bonsai mix. | Source

Ok, so Soil now what?

Soil used in bonsai is a very widely debated issue due to every hobbyist having their own recipe mix for their soil; hence, one person’s soil composition for tropical trees may be too light or too heavy to another. Some people will even mention that bonsai soil is not even soil at all as it can contain no soil in the traditional sense. Many people will prefer to call their bonsai substrate “mixes” to back away from actually calling it soil to mitigate confusion. Regardless of what you put in for any tree; the real difference between the traditional sense of soil and bonsai mix is that drainage is optimal and the main goal to achieve.

Why is Drainage Important?

Why is drainage key to growing healthy bonsai? You can ask yourself "If that’s my only concern, I’m sure it can be solved by my pot having holes, I’m sure it will drain regardless how much water it has in it, right?" Well, the question is not entirely wrong but is the key factor to several issues, starting with #1, of allowing water to drain quickly will spare the tree from suffering “wet feet” which leads to root rot. You are welcome to place a tree into a densely packed pot of soil; however, you might not have a tree that’ll be as healthy as a tree placed into efficiently draining soil; which brings us to issue #2. It’s rational to imagine densely packed soil that does not allow water to drain will also not allow air to permeate soil. Starving roots from oxygen can result with roots not growing properly which will result in weak trees that will not allow the tree to be secured properly.

General Knowledge

Without being informed that bonsai soil is not really soil, would you have known that there was a special type of soil mix specifically for bonsai?

  • Yes, knowing that bonsai is special, I would assume it's not a simple as using regular dirt.
  • No, I had no idea bonsai had it's own soil, I would just use regular dirt.
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What are the Components?

Bonsai mix can be separated into two categories, Organic and Inorganic. The difference between organic and inorganic is based on water retentiveness. Both ingredients have grit which allows for excess water to drain from the mix. But aside from that, the names for both are literal as organic components have decaying plant matter; while inorganic ingredients are comprised of no organic matter like rocks and other gritty material like baked clay. Unlike days of the past when baked clay was not as readily available, organic matter was more favorable. However, traditional mixes were a danger to the possibility of over watering and a dramatic shift towards inorganic matter is now on the rise. In modern times, growers who use a mix of high fired clay and other gritty material that are great water retainers; yet, coarse enough to encourage root growth, can water multiple times a day without over watering. There are some growers who grow their trees in pure baked clay for maximum water drainage and maximum oxygen permeability. But should be cautioned loose mixes can disrupt root growth due to shifting.

Small sized pine bark to be used as organic aggregate.
Small sized pine bark to be used as organic aggregate.
Peat moss. Once wet, peat moss is an amazing bonding agent.
Peat moss. Once wet, peat moss is an amazing bonding agent.
Potting soil.
Potting soil.

Organic Component

Organic components comprise of conifer bark, peat moss (humus), potting soil and any other composted material. To go into further detail:

  • Conifer bark as a soil conditioner can add bulk to the mix and can retain moisture; while allowing excess water to drain.
  • Peat moss (humus) is what retains the most water and therefore should be used sparingly. This material is really used just to bind the material together so the different components do not shift around as roots are growing. It's important to know moss can hold a substantial amount of water and without proper drainage, it can hold onto a large amount of water for a long time.
  • Potting soil will add bulk to your mix as well as used as a bonding agent. Be aware potting soil is highly water retentive.
  • Decomposing plant matter is added as feed.

This is akadama, the high fired inorganic component. Notice the small granule sizing.
This is akadama, the high fired inorganic component. Notice the small granule sizing.
Turface, very similar to akadama, is also a high fired clay. Notice the size comparison next to a quarter.
Turface, very similar to akadama, is also a high fired clay. Notice the size comparison next to a quarter. | Source
Lava rocks, another great coarse aggregate used in creating your perfect bonsai mix. Notice the dime used to reference the small size.
Lava rocks, another great coarse aggregate used in creating your perfect bonsai mix. Notice the dime used to reference the small size. | Source
Diatomaceous earth compared to a dime.
Diatomaceous earth compared to a dime.

Inorganic Component

The key to inorganic components is to add "grit" to a mix. The more grit you add the more aeration it allows and that will help stimulate strong root growth. Inorganic components consists of other materials that do not break down like the organic counterpart. Most inorganic components are highly prized for their porous properties that can retain water but does not break down as quickly or condense. Here are various types of inorganic components:

  • Akadama: this is a hard fired clay and great at retaining water. This component is ideal for mixing bonsai soil. It is often considered to be a mandatory component when creating your bonsai mix. The only problem with this is it will break down in a few years.
  • Turface: this looks a lot like the high fired akadama clay but it isn't. This material is mainly used for the underlining of golf courses and baseball fields as it does wonders of allowing air to penetrate; thus, making it perfect for grass.
  • Lava rock: this material is incredibly coarse and porous. Unlike the other two mentioned before, this component will not breakdown as easily. People like to use this as a top dressing for their gardens, but have no idea how incredibly great this serves as an aggregate in bonsai mixes.
  • DIATOMACEOUS EARTH: This material is a bit out of the ordinary and is only advised should you not find anything else mentioned on the above list. Diatomaceous earth aka Oil Sorb or Oil Dri, is used by mechanics who spread the stuff onto the floor in case of oil spills. The material will soak up the oil and will make clean up a lot easier. In bonsai it works in the same principle, it will soak up water and retain moisture but still hold onto it's coarse shape allowing roots to grow around it. If you are able to obtain this stuff, make sure to confirm the material is #8822. This is tried and tested and will not turn to mush.

Additional Soil Conditioners

The different components mentioned above is only a little of what can be used in bonsai. There are various other soil conditioners and soil aggregates that can be used in mixing your own bonsai mix. The important factor to know is will your addition provide the three goods:

- good aeration

- good drainage

- good moisture retentiveness

These should be the three guidelines to consider when adding other components to your mixture. Some may be conventional and some may be out of the book suggested by a person whom you trust knows that works. You just have to try it yourself to confirm and conduct tests. One can not go wrong with either organic or inorganic components, just as long as it provides those three things.

Soil sifter.
Soil sifter.

The Right Equipment

Component aside, the right equipment will allow you to get the best out of your material. When talking about equipment, I mean a sifter. Your material, which will come in bags or sacks will have a lot of impurities and those impurities can range from dust, to just various other nasty things that you don't want. For example, you'll want to get rid of dust as dust can settle and clog holes through time. Other impurities like grass and possibly other organic matter can do the same type of damage. Sifters will allow you to sift the material through various levels which will allow you to have smaller granules for smaller potted bonsai to larger granules for larger bonsai. Sifting is not necessarily an important step; however, it is highly and sometimes strongly recommended because you paid a lot of money for your material, why not take the additional step.

Mixing Recipes

As mentioned above, there is no one way to approach your own unique mix. There are a few guidelines that many can suggest but be aware that they are just suggestions. As a hobbyist in bonsai, it's important to be open minded and try it your way before dismissing or criticizing. What may not work for you will work for someone else. As there is a clear guideline for various types of bonsai, mixes will have to correlate to match the specific types of trees.

Bonsai Mix Recipe

Organic/Inorganic Compoents
Basic Bonsai Mix
Tropical Bonsai Mix
Deciduous Bonsai Mox
Conifer Bonsai Mix
Lava rock/Diatomaceous earth
Organic Compost Component
The different types of balanced ratio of organic to inorganic mixed with grit to create a well balanced bonsai mix for various types of trees.

Clump vs Loose

After a period of time, soil will condense and that will be considered as your testing period. How well your soil will hold up will tell in the health of your tree. To simulate that type of compaction, even before you fill the pot with your bonsai mix, you should be able to squeeze a big clump of whetted mix in your hand. If the mix compacts and stays like a ball, your mix is too full of organic matter and will retain a lot of water. Should the mix fall away after you release it from your palm, you have a good well draining mix. To correct either too lose or too compact, simply add to the mix of either more grit or more organic matter to fit your needs.


Mixing your own bonsai mix is a great sign of dedication. Your love for your tree starts from the ground up. Mixing your own bonsai mix will allow you to understand your tree a lot more. A tree will often be able to tell you how it feels and will let you know what its needs all based on its mix condition. A good mix will allow the grower to know when the tree needs water and the condition of the tree. A good mix can determine how much training a tree can endure this year. A bad mix will result with a delay in growth and as well in health. A sick tree is limited in what it can do and often times, the grower's simplest demands are all too much for the tree. Take care of your tree by giving it the best soil mix you can muster. I never asked the stupid question until late in the hobby, I hope this comes to you early in your journey as this is an important aspect to bonsai.


David 7 months ago

Have you ever used crushed granite as part of the bonsai mixture? I recently made my own soil using it along with perlite and organic soil dug up from my father inlaws barn. The tree I placed in the mixture was a bald cypress that I had left in an old goldfish pond for 3 yrs trying to increase the size and look of the J

nabari, I planted it in early February and I'm very impressed with the amount of buds I have! I'm thinking of doing the same to my crape myrtle that's been in a bonsai pot for 2 1/2 years.

Any advice would be appreciated! Thanks

David 6 months ago

Crushed granite has been used and mainly used to add drainage. It's heavy and it's not very porous so it's really there to add grit to the mix. I wouldn't just use the granite in a high concentration because like mentioned, it doesn't hold that much water. But with the perlite and organic soil, it should help. Good on you for keeping it in the pond btw!

Vinny Chirayil profile image

Vinny Chirayil 2 months ago from Hyderabad, India

Good article and I relate to the question "why not have pots with holes". I believe good drainage & aeration begins with the pot, not bonsai soil. That comes later. But many bonsai experts & their followers seem ignorant of this, judging by their training / grow pots (not words). I have elaborated this issue in detail, in the article 'Colander vs. Bonsai Pot' -

Opinions, thoughts, counter-points, perspective etc are most welcome.

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