Warren Hill Soil Experiment

This article was originally written back in May 2006, to document an experiment that I conducted using various substrates.

Background
A recent debate, which took place on several forums with regards to the continued use of “Turface” or any other calcinated clay or similar soil amendments with high Cation Exchange Capacities (CEC) in our substrate, would lock up needed nutrients, leaving an accumulation of unwanted salts, which in turn leads to the poor health and perhaps the eventual demise of our beloved trees.

Aim
In light of these posts, I have decided to conduct my own experiment, to satisfy my own curiosity and is not intended to debate “soil recipes” but rather discuss the merits or discredit some of Mr Hill’s fore drawn conclusions.

The subjects I have chosen for my experiment are: the Cotoneaster Horizontalis var. Rockspray. I have chosen this particular type of tree because it has demonstrated in the past they adapt well to my short growing season and climate here in Nova Scotia. The substrate I used was: my 30/70 mix (bark, turface & grit, 30/35/35), Turface and Chicken Grit (ground granite).

Discussion
At the centre of the debate was the reputation and teachings of renowned Bonsaiist Warren Hill. Mr Hill is a gifted and talented bonsai artist who has spent the better part of his life in the pursuit of better bonsai and better bonsai technique. He is a world famous, world-class teacher and educator on this subject who has earned that reputation and international regard by being able to actually do it. One look at any bonsai he has created will immediately make this clear. He worked for the US Department of Agriculture for close to 40 years. During his tenure he had access to the necessary equipment and materials he needed to derive his conclusions.

During his lectures, Mr Hill professes that 80% of our trees either die or never reach their full potential because of unwanted salts in our substrate. Warren’s recipe of choice is: Akadama or similar; Sphagnum Moss; and builders sand or grit. His claim is that Akadama has a lower CEC than the calcinated clays, and albeit water retentive Sphagnum Moss was relatively neutral with regards to initial salt content and the remaining ingredients mentioned nil. He further lectures against the use of any type of Chemical Fertilization and goes on to say that one should only use organic fertilizers, in particular, fish fertilizer. It should be also noted that Mr Hill lived a good portion of his life in Southern California, a place denoted for the high sodium content in the drinking water. What is unusual in my opinion is that in all his lectures he fails to mention the use of distilled water when faced with high sodium content of drinking water in individual locales. Albeit, void of any trace minerals and nutrients, one would think the benefits of using distilled water would outweigh the negatives “as professed” of using drinking water with high initial sodium content?

Another interesting tidbit of discussion took place on the Bonsai Site where: “Grouper52” an MD by profession, challenges Warren’s findings as inconsequential from strictly a scientific point of view. That particular post was thought provoking indeed, from a strictly clinical point of view in my opinion.

Probably the most heated debate on the subject can be found at Bonsai Talk The thread was started as on the previously mentioned site by the same hobbyist whom had recently returned from a lecture given by Mr Hill. This hobbyist only recently commenced his journey into our beloved art. This particular thread contains a good explanation on CECs, the interlocutor, “Forest Reef”. Of note, “Forrest Reef” is a student of Mr Warren Hill. Nonetheless, her discussion is pretty candid and contains several links to the topic in question. I have added the links to these articles at the end synopsis for your interest and viewing pleasure.

Experiment preparation
As previously mention I purchased 3 cotoneasters for this experiment. I chose 3 relatively similar trees with regards to health and size, keeping in mind that albeit an experiment, I wanted to be able to continue developing and enjoying the trees in the future. I did pay attention to the nebari and trunk development of the purchased subjects. Because of the short growing season in Nova Scotia, I purchased 3 pond baskets for growing containers. My rationale was to provide my trees with the most advantages I possibly could with limited growing resources. The free flow of oxygen and fast drainage of pond baskets, would lead to phenomenal root production and eventually top growth.

The Subjects
From top to bottom: “My soil”, Turface and Grit. Albeit still in their nursery containers, for the purpose of this article, pictures of the subjects (unless stated otherwise) will always take place in this order.


My soil


Turface


Grit

… after washing the roots.


My soil


Turface


Grit

The entire “old soil” was removed from the root ball using a garden hose. The roots were healthy and had many fine feeders. The taproot was removed from all 3 subjects and all received a minor root trim. In doing so I tried to keep the root ball roughly the same size for all three trees.

… ready for planting


My soil


Turface


Grit

The trees were planted in pond baskets in the following formulation from top to bottom: My 30/70 mix composed of 30% bark, 35% turface and 35% grit by (volume); 100% turface; and 100% grit.

… after original styling


My soil


Turface


Grit

Once the trees were transplanted, it became necessary to wire the trees to the baskets. The later was accomplished using loose guide wires vice securing the root ball to the baskets. Each tree received its initial trim. I tried to keep the trimming as equal as I possibly could given the state of branching and foliage. Once complete, each tree was watered thoroughly, allowed to soak for 15 minutes, watered again, again allowed to soak for 15 minutes and given an initial feeding of 10-52-10 “transplant fertilizer” at half strength to assist in alleviating transplant shock. All trees were placed in partial sun for 1 week. When signs of growth appeared they were in turn placed in full sun. Their watering requirements varied in the beginning, especially the one with the 30% organic mix. It received water every two to three days depending on the temperature, whilst the remaining two where watered once a day and twice a day respectively, on really hot days, the “grit tree” was watered 3 times a day.

Transplanting took place on the 5th of May. On the 19th of May they received another dose of 10-52-10 this time at full strength. I have been doing this with all my trees and have enjoyed great success since beginning the practice.

Beginning with the first week in June, they were placed on my Feeding Program for flowering/fruiting trees. The following table depicts their feeding regimen:



Progression
The trees are receiving weekly maintenance pruning e.g. allowed to grow 6 to 8 leaves and trimming back to just two. The tree growing in “my soil” receives a monthly flush, my rationale for the latter is that the organic components of the mix will “hold on” to the feed relatively speaking, compared to the other two. Although extremely early in the experiment as of the 12th of June, the tree that has demonstrated the most growth has been the one in the organic mixed followed by the tree in 100% grit. I will be following the progression carefully to see what might have led to this spurt if anything.

A year later…
Today, a year and a week later I decided to see what transpired over the past year. The tree that prospered the most was the tree planted in my soil recipe, followed by the tree in straight Turface, whilst the “pure grit” tree picked up the rear.

When I removed the trees from their individual baskets, the soil fell away from the root ball of the “grit tree” whilst a good portion of soil remained in the other two and had to be washed away. The roots were able to attach themselves to the medium so to speak. Although the grit tree’s bottom development was not as prolific as the others, I don’t believe it to be a determining factor in this instance. My observations lead me to believe that pure grit makes for a lousy anchoring medium when compared to the other two. As proper anchoring is an important factor in root development, I cannot endorse the practice of using pure grit as a growing medium without adequate support. All the trees had a healthy root system with no sign of rot of any kind. The only difference noticed was the root mass of the trees.


My soil


Turface


Grit

Although the top growth is really apparent in these photos, the real growth occurred in the baskets.


My soil


Turface


Grit

...and


My soil


Turface


Grit

Conclusion
They say a picture is worth a thousand words, in this instance the proof is in the pudding. As previously mentioned all trees received the same treatment during last years growing season. They were fed at the same rate; the only differential treatment they received was individual watering, because of different evaporation rates and moisture retention. As previously mentioned, the tree growing in the organic medium received a monthly flush, the latter was performed to level the playing field so to speak as the CEC of the organic mix was/is greater than the CEC of the inorganic mediums.

What can be drawn from this experiment? I believe a year is insufficient time to really evaluate the retention of unwanted salts in the mediums, as Warren would claim. I further believe that individual climates play a large role in growing bonsai. Warren is from California where the sodium content in their water is prevalent and evaporation rates higher. I believe this is an important factor that was overlooked and is not mentioned in any of his debates. Although, Warren’s test results may be valid, I dare venture to say that I further believe the results would have been different if these test/experiments were conducted elsewhere in the country, in order to draw precise and valid conclusions. Warren’s claim that the growth in a medium with low CECs exceeds that of any other soil composition, in this particular case the evidence speaks for itself.

Although the tree potted in pure grit survived the season, it did not flourish perse. I believe the tree in this instance may well have been under nourished due to the low CEC of the grit when compared to the other two mediums, with the organic medium having the greatest CEC of them all. An interesting observation was the prolific bottom growth of the tree that was planted in straight Turface; it demonstrated similar bottom growth as the organic tree and was only slightly behind. The top growth although better than the grit tree was not as prolific as the organic one. This is amazing as the basis of this debate was that Turface or any other calcinated clay product was bad for your trees.

Will the health of trees planted in a calcinated clay environment decrease over time? Perhaps but, one cannot deny the growth compared to the “grit tree”. It is my opinion that the accumulation of unwanted salts is a moot point if the tree is properly fed and watered, with periodic flushing and re-potting. Another point to note; was Warren over feeding his trees? The latter would only exacerbate the accumulation of salts in his medium, considering the original high sodium content of their water.

The reason for my experiment was to satisfy my own curiosity with regards to growth rates when potted in differing mediums. As previously mentioned, it was too early to tell if the accumulation of unwanted salts would play a factor in the trees future. When comparing growth; we have to concede that a tree planted in a free draining, well oxygenated soil, suitable for ones climactic conditions, will indeed prosper. I further believe that the reason the tree planted in the organic medium benefited of the extra Nitrogen produced by the slow decomposition of organic matter. Although the decomposition may have been low, it is nonetheless a factor that should not be overlooked when compared with the Turface tree.

In my opinion it is indeed possible to mimic the growing conditions across growing mediums by altering the feed rates and fertilizer values used, the latter is impractical in my opinion. Testing soil for the presence of specific nutrients and minerals is best suited for laboratories than someone’s bonsai garden. I further believe the average enthusiast has better things to do in the daily maintenance of his trees vice analyzing soil composition and thus adjusting feed/component rates

In closing I believe the low or lack of CEC of pure grit compared to other mediums leads to under-developed and under-nourished trees. Furthermore, pure grit makes for a lousy anchoring medium. Although this experiment did not refute Warren’s findings, I believe the results of this little experiment to be of some value. Everyone is in search of the “magic” soil recipe. It has been said time and time again that a good recipe is one that works for you, under your growing conditions, in your region. Therefore, I believe that a good growing medium must be relatively cheap, components readily available and provide a free flowing, oxygenated environment for your trees to truly prosper. I believe that a well-balanced feeding schedule with periodic top flushing and adequate re-potting intervals will alleviate if not eliminate unwanted salt accumulation. I further believe that a container of the proper size for the trees growing characteristics, not to mention growing climate is of paramount importance vice the medium it is planted in, in order to maintain healthy prosperous trees.

Disclaimer
The aforementioned experiment was not conducted under scientific conditions, to do so as discussed, would take years. For the experiment of unwanted salt accumulation to be credible in my opinion; it would need to be carried out in varying parts of the country, where trees are potted up in exact mediums, watered using distilled water of known quality and specific ppm, fed the same amount and brand of fertilizer, and potted in suitable containers of the same size. The aforementioned discussion is merely my observation of growth rates in varying mediums.

Links
Soil in a container - Electrical conductivity
Warren's Site
Bonsai Talk
Bonsai Site