At Bonsai Empire we receive questions about Akadama, and its use for Bonsai soil, quite a lot. With the recent price increases, troubles in supply and proposed alternatives (including cat litter) people seem to be in doubt whether or not to use Akadama at all.
Many factors come into play when trying to say anything sensible about Bonsai soil (climate, tree-species, stage of development of the tree, etc); this article generalizes some of these factors to not over-complicate the issue even further.
As I don't consider myself an expert at Bonsai soil mixtures, but do like to be able to provide my website visitors with an answer, I decided to ask a few people that I personally consider experts at Bonsai. Boon Manakitivipart (Bonsai Boon), Colin Lewis, Harry Harrington, Morten Albek and Robert Steven were kind enough to share their personal opinion about Akadama, answering five questions about Akadama and its use in Bonsai soil mixtures. Enjoy reading!
Expert opinions on Akadama for Bonsai soil
The experts answer a few questions that Bonsai Empire asked them about Akadama, and its use as Bonsai soil. You will find their exact input below.
(1.) Do you use akadama? If so, for all your trees? And for trees in all stages of development?
Yes, I use akadama for all my trees. I use less akadama on the tree in training (25% or less). - Boonyarat Manakitivipart (Bonsai Boon)
I try to use Akadama for Japanese maples since I have found nothing better. Unfortunately price and unreliability of supply in the USA means that this is not always possible. I also use recycled Akadama as a partial ingredient in general purpose soils. - Colin Lewis
I haven't used Akadama on my own trees for over 10 years now; there have been occasions a client has insisted on using it for deciduous trees (that can be bare-rooted) but I always refuse to repot a coniferous species into Akadama. Pines and Junipers cannot have a complete soil-change to remove Akadama and repotting is infrequent; it stands to reason that any akadama introduced into the soil of a Pine or Juniper will become very compacted before there is an opportunity to remove it. - Harry Harrington
The answer is simple, because I do not use Akadama. Have tried it and it doesn't do its job here. It doesn't fit the growing conditions around here (Northern Europe), it is expensive, and other high quality soils are available at low costs. Denmark is a country with a proud gardening history and a well developed greenhouse tradition, which has contributed with a lot of research and development bringing forward the best soil mixtures for container growing i.e. So why import a soil when very good and tested soils are at hand? - Morten Albek
No, in Indonesia, we only use volcanic lava soil from Indonesia for all of our Bonsai. for all stages. Excellent and cheap! - Robert Steven
(2.) If you use akadama in soil mixtures, would you share what mixtures you personally use?
Our soil recipe contains, 1 part lava rock, 1 part pumice, 1 part Akadama, ½ cup of horticultural charcoal (per 5 gallon mix), ½ cup of decompose granite (per 5 gallon mix). For deciduous, use small size mix (1/16”-1/4 “) and add 1 extra part of Akadama. All ingredients must be bone dry, screened and sized. The dust is discarded. The use of pumice for bottom layer drainage (5/16 “) is recommended.
For conifers from the desert and high mountains use medium size mix (3/8” – 5/16”). For lower elevation conifer and water loving conifer, use small size mix (1/16” – 1 / 4 “). Note : Proper repotting technique needs to be applied, otherwise this mix is not recommended. For best results, organic fertilizer is recommended at the correct times and season. A thin layer of coarsely screened New Zealand sphagnum moss should be place on top of the new soil. The moss will keep the soil in place during watering. The thickness of the moss layer should vary according to climate and watering habits.
This soil mix has been used successfully throughout North America. - Boonyarat Manakitivipart (Bonsai Boon)
This depends on what is currently available. Some turface, lava and/or pumice, plus some organic (to create a 'living' medium) and plenty of coarse sand to ensure adequate drainage. The proportions of organic and sand varies according to species. - Colin Lewis
The soil mix I use for all of my trees contains certain brands of cat-litter available in the UK (Diatomaceous Earth or 'Diatomite') and various amounts of chopped-bark, depending on the water retention required according to the tree species, vigor of the individual tree and even the shape of the Bonsai pot. (Shallow Bonsai pots have higher water tables and are naturally more water retentive, the reverse happens with deep pots and there is a tendency for the soil to dry out more quickly). - Harry Harrington
I use sphagnum peat for trees loving an acid soil (like Azalea, which loves this soil), and alkaline basic nursery soils for other trees. Available at good garden centers. This I mix with pebbles of Leca or lava e.g. to adjust transpiration and drainage. Shohin Bonsai gets a mixture with up to 80 percent soil, and 20 percent drainage pebbles or small stones like lava pebbles.
For large trees that doesn't want a free draining soil, a app. 50/50 mixture is used as basic soil mixture. Pines, and other trees who needs a very free draining soil is planted in 70 - 90 percent Leca pebbles and 10 - 30 percent sphagnum peat mixed with a normal garden soil for greenhouse plants. - Morten Albek
We use 100% volcanic soil without any mixture except adding the slow release organic fertilizer (sun flower seeds made). That's it. - Robert Steven
(3.) When using akadama, how often do you repot your trees? What is your experience with akadama breaking down, as in, after how many years?
Depends on the size, age, container shape and size and type of your tree. Shohin are repotted once a year. Medium sized conifers are repotted once a year or every other year. Old and larger conifers, once every 2-5 years. - Boonyarat Manakitivipart (Bonsai Boon)
I think many people repot their trees too often - three years should be the minimum period between each repotting. Akadama does break down. The cheaper grades break down more quickly than the better grades, and the surface breaks down quicker than lower in the pot, but it still drains well and performs as it should. It's not clay, so the particles do not adhere to each other. Trees grown in pure Akadama seem to require repotting less often than those grown in other purely mineral soils (see 4, below). - Colin Lewis
Akadama breaks down over 1 to 2 years, depending on the quality of the akadama, freeze/thaw cycle in your climate and frequency of watering. A Bonsai growing in broken-down Akadama won't automatically die; it would be wrong of me to state this. But as with all broken-down, airless clay-soils in Bonsai pots, drainage is poor, absorbance of water into dry akadama is poor, and the overall health of the tree as well as its vigor is greatly reduced. Unless the Akadama can be completely removed (the tree bare-rooted) every two years, it should quite simply not be used. One misunderstanding that many enthusiasts seem to have is that although Akadama has been used for many years in Japan; this is not because it is the 'best' soil for Bonsai. It is simply because in Japan it is, or at least was, a relatively cheap and freely available to enthusiasts. - Harry Harrington
Not using akadama is because it easily breaks down in freezing periods. Even the harder akadama types are not resistant over longer time spans. Akadama is a clay soil, and will be very compact and poor of oxygen, harming the roots when broken down. After only one or two seasons the akadama will break down and begin decreasing its value is the experience I have. Trees imported from Japan growing in akadama soil have all proven very big problems surviving. The Japanese climate, and their lacking availability of other soil types makes akadama their choice. The humid Japanese climate during summer and frequent repotting of trees, practically makes akadama a favorite choice of Bonsai soil there (also economically compared to importing soils). So if you live in an area comparable to the Japanese climate akadama might be your choice, or maybe you find another source better suited (both practically and economically). - Morten Albek
I did tried Akadama many years ago for few of my Bonsai. it broke down after 2 years or something, and I didn't find any better than our volcanic soil but very expensive, then I stopped. - Robert Steven
(4.) Do you have experience with possible alternatives to Akadama, like cat litter, turface, Primera one, permatil, mule mix, Calidama, Mocha Lava, etc?
No there is no possible alternatives to Akadama. If it is not available, I will use lava, pumice and small amount of charcoal and crushed granite (clean sifted, free of dust). - Boonyarat Manakitivipart (Bonsai Boon)
No other mineral component is a substitute for Akadama because roots can penetrate each grain of Akadama but cannot penetrate other minerals. This means that in 100 percent Akadama roots have 100 percent of the pot volume available for growth. In a mix of other mineral ingredients, the roots only have the space between the grains, which may be as low as 30 percent of the pot volume. Products like Turface are soil amendments that the manufacturers recommend using at no more than 10 - 15 percent of the total volume. I follow that recommendation. I have noticed that turface gives good results for a year, possibly two years when used for newly collected plants, but during year three there is a deterioration in vigor at the time when one would normally expect an improvement. Cat litter is a similar product to turface, but may contain contaminants, so I avoid it. I have used lava a lot, and I am impressed by the results I have seen with newly collected plants. Lava appears to contain available beneficial minerals, although I have no scientific evidence of this. But I find that at lower levels in the pot the rough texture of the grains holds too much water by surface tension which, ironically considering the large particles, impedes drainage. An additional problem with lava is that the surface has sharp edges that can easily damage tender roots during repotting. This means that extra care must be taken when working a lava-rich soil between the roots. Pumice is an improvement on both turface and lava. Surface texture, water retention and drainage are all near optimum, although roots still can't penetrate the grains. - Colin Lewis
I have experience of using turface, seramis, cat litter on my own trees and experience of a wide range of alternatives used by clients on their Bonsai. I have been using Diatomaceous Earth or 'Diatomite' (Catlitter) on my trees for around a decade now. Read more about this here. - Harry Harrington
I mostly use sphagnum peat (not to be confused with the fresh mosses used for air layering i.e.) for trees loving an acid soil (like Azalea, which loves this soil), and alkaline basic soils for other trees, generally all based on a good soil structure that is water holding and at the same time have a high level of oxygen. All available at good garden centers. This I mix with pebbles of Leca or lava e.g. to adjust transpiration and drainage. Have worked very well for my Bonsai growing during 20 years now, and therefore I have had no reason to experiment with soils not having the quality I want. - Morten Albek
No experience other than volcanic material. - Robert Steven
Akadama is a Japanese baked clay.
(5.) Any general comments you like to share when discussing the topic "to akadama, or not to akadama"?
I use Akadama because it is one of the best ingredient to use. But you need to know how to use use it. You need to learn how to repot and remove and add soil properly. And then learn how to water and fertilize properly. I used to suggest and argue on the soil subject. Now I do not do that. If you decide to use organic and potting soil, you are not with me. And you will never know what the good healthy roots look like. - Boonyarat Manakitivipart (Bonsai Boon)
Back in the dark ages before Akadama was available in Europe I used a combination of coarse organic matter (sifted peat, pine or oak leaf mould, genuinely decomposed bark) mixed with coarse sand and a handful of turface. I can honestly say that the results were as good as they are with Akadama. The big difference being that with Akadama the repotting process is easier since the roots are not entangled with fibrous organic matter. Frankly, in the USA Akadama is becoming so expensive that a cheaper, viable alternative must be found. For many species native to my area (picea, larix, abies, native acer) I am resorting to organic and sand, with about 25 percent recycled akadama/lava/whatever. For native pines I use one part of the above recipe with two parts sand. - Colin Lewis
In brief; there are still a number of enthusiasts that have used Akadama exclusively or as part of a soil-mix for many years, and their Bonsai will not have exhibited /obvious /signs of ill-health as a direct result of using Akadama. And understandably, they will not have reason to question its use. But I firmly believe, as do an increasing number of people over the past decade, that Akadama does not realize the true potential, health and vigor of a Bonsai or in many cases, is the underlying cause of weakness, susceptibility to fungal or insect attack or even death (in irregularly repotted trees). - Harry Harrington
Akadama is a Japanese soil, located in Japan, and useful in Japan. It is not a perfect or mysterious receipt solving any problems or making any Bonsai look better. It is a soil, and not made for Bonsai only. Several other types of soils will do exactly the same job, with differences in handling its job, primarily depending on climate conditions and the growing demands of the tree it serves. Twenty-five (or more) soil combinations may fore-fill the exact same purpose. So no exact formula is the one and only. We all have different experiences based on climate, local conditions (as down to how the Bonsai are placed in the garden like in semi-shade, a hot place with stones on the ground warmed by the sun, a humid area with a moist ground i.e., or how we water and feed, how well we transplant our trees, how much knowledge we gain, and so on. Bottom line, make your own experiences and do not use money at a advertised "quality" akadama because it is Japanese, or because your Bonsai dealer tells you to use a Japanese soil, because Bonsai is Japanese. Your trees are growing at your destination, and must be treated that way. Depending on where you live, find a soil that fits your needs, and be happy with what works for you. But akadama is not doing it´s job for me. Whatever soil type you may prefer, make sure it is heat treated to solve any issues with diseases or pests, and therefore it is advisable newer to use any soils from the garden. Buy a good soil in a garden centre, and not the cheapest one, because they break down too fast. - Morten Albek
I believe Akadama is good, but just not better than our volcanic soil. The most important thing for Bonsai soil is all the characteristic features, and we found them all better in Volcanic soil. I used to export a lots to many countries, especially Thailand, Malaysia, Taiwan and China, but we are no more allowed to export. - Robert Steven
(6.) Could you please describe your local climate, and how this affects your choice of soil mixtures?
I live in USDA zone 10a (with a range of 35 to 40 F). We get cold in winter to get frost at night and rarely snow. In summer we have cold fog coming in from the ocean. It is on the cool side in summer here in San Francisco Bay Area. Our trees grow slower in the cool summer. - Boonyarat Manakitivipart (Bonsai Boon)
Temperatures range from a normal summer high of 38c to a normal winter low of -25c, in Southern Maine, USA. We have an average _total_ snowfall of 2.5 meters. Rainfall is no more no more nor less than the European average. Climate does not affect my choice of soils since I can control watering during hot dry weather and it never rains so much for so long that excess water becomes a problem. - Colin Lewis
I live in the UK, typically the climate has highs of around 30C in the Summer and lows of -5 to -10C in the Winter. Rainfall levels are fairly high and the freeze-thaw cycle is regular, particularly from January through until April. A water-retentive but well-drained soil is therefore essential for my Bonsai. - Harry Harrington
The climate in Denmark, Northern Europe, shows sometimes very shifting conditions. Summers may vary from long hot and dry periods, to rainy periods. Highest temperatures varies from 60-90°F (15-32°C). Winters sometimes are very cold, and other years very mild. One season can present temperatures as low as-10 to -20 degrees in periods with snow, and some winters shows between 5 - 10 degrees above freezing, with minor periods with frosts. Rainy periods often are in autumn, and summer showers shows too. Milder winters have often pretty much rain, and cold winters are very dry. My Bonsai are always stowed in a cold frame greenhouse. Either for protection for cold winds or for heavy raining periods. Trees are paced under the sky from midd March to November. - Morten Albek
We are truly tropical with only warm and raining season; and we are mostly working deciduous trees, not much on conifers. We are starting junipers and black pine, and seems they are growing well with volcanic soil, so we are not considering others. - Robert Steven
Conclusion, to Akadama or not to Akadama?
As you have noted by now, there is no unchallenged or straightforward answer to this question. Some experts endorse the use of Akadama, while others (the majority of experts we interviewed) prefer different types of Bonsai soil. The discussion above does reveal the importance of one matter; the question whether or not Akadama is a good soil for Bonsai depends very much on your climate, your budget, availability of alternatives and how you use soil in the first place. Thus, while the main question is left unanswered, the experts did help us understand much more about the use of Akadama. Hopefully enough information for you to decide for yourself what's best for your trees! Finally, a big thanks to the contributing experts.