by George Buehler

When I was at the ABS learning seminar, one of the classes I took was on fertilization, given by the curator of the Montreal bonsai exhibit, David Easterbrook. During that class, David stated that they have started using a micronutrient called MicroMax. They found that for the various trees they maintain, each performed much better when treated with MicroMax than those trees not treated. Growth was much better, leaf and flower color was much better, and the general health was much better. He also stated that they have given up using any kind of 'vitamin' supplement.

It sounded too good to be true. However, there was a vendor at the seminar who was selling the product, so I purchased a bottle to give it a try. An 8 ounce bottle of the stuff cost $5.00. The label states that the 8 oz bottle treats 60 gallon of soil (1/2 level teaspoon per gallon of soil). The label also states that higher concentrations should not be used – no reason given. There are also the usual caution labels that are now required. The manufacturing company (Scotts) recommends that the product be mixed with the soil prior to putting the soil in the pot. However, they also state that it can be sprinkled on top of the soil in the spring at bud break and watered in.

When I got home, I picked several trees to try it on. I calculated the volume of soil in the pot and sprinkled the appropriate amount on top of the soil. Then I watered it in, per the instructions. Of course, it is too early to say what the results will be. That will be a future article - I hope.

In the mean time, as most of you are aware, I have a tendency to question things, so I went to the net to see what the researchers said about the product. The MSDS (Material Safety Data Sheet) reports that it is a fine white powder that is 70% soluble in water (although looking at the material in the bottle, it looks more like a granule rather than a powder). The ingredients list shows that it contains iron sulfate, manganese sulfate, copper sulfate and zinc sulfate,S which should give it an acidic characteristic. The MSDS also lists sodium borate, sodium molybdate, calcium phosphates and dolomite in its ingredients¹. Since the product is 70% soluble and it is targeted toward greenhouse growers, I would think that after the first watering in our bonsai soil, most of the product would be washed out. However, I couldn't find any reference to such a phenomenon.

One of the leading authorities on growing plants in containers is Dr. Carl Whitcomb. Dr. Whitcomb has published many articles on growing plants in containers, given a number of seminars on container growing, and has published several books. Although most of his research has been targeted toward growing food stuff plants, a lot of the information he has published can be utilized in bonsai horticulture if the appropriate cautions are used.

In the late 70's and early 80's, Dr. Whitcomb set up a study using 243 micronutrient combinations with tomato, azalea and Pyracantha as test species². In this experiment, all the plants treated with what would eventually be called MicroMax were analyzed and found to have much larger top growth, had darker green leaves and, when ashed, had higher amounts of the essential micronutrients – iron, zinc, and manganese. Based on these studies and a previous smaller study, Whitcomb obtained a patent (US 4328025³) for the MicroMax (he originally wanted to call it "Keep Really Attractive Plants" or KRAP but since he quickly sold the rights to the patent, that name was dropped).

What I find interesting about a number of "studies" Whitcomb reports in his book (Plant Production In Containers II), is that he mentions use of several different types of Osmocote along with the micronutrients. I had no way of knowing which affected the results more – the micronutrients or the Osmocote. Or perhaps, the MicroMax enabled the plants to better utilize the Osmocote. Since I was still looking for an answer, I started looking at some other research reports.

One report⁴ listed a number of nutrient experiments, one using MicroMax. In this report, Browder states that for the plants studied – Pin Oak and Japanese Maples – the concentration of sulfur was more important than the use of MicroMax. The Scotts Company latest spec sheet lists the sulfur concentration as 12% (Iron 17%, Calcium 6%, Manganese 2.5%, Zinc 1%, Copper 1%, Boron 0.1%, and Molybdenum 0.05%). It would have been nice if Browder had repeated these experiments on other plant types. High sulfur additions would make the soil medium slightly acidic, and both oaks and maples prefer slightly acidic soils. So perhaps Browder had set up his experiment to help prove what was already known.

Although the label directions on the bottle of MicroMax states the product can be sprinkled on top of the soil, Altland and Fain⁵ report that better root results and less weed growth were obtained when the material was incorporated in the soil. Interestingly enough, they also report that when using slow release fertilizers (Osmocote), better results were obtained when the srf was concentrated in selective areas of the pot (i.e. a hole punched in the soil and the srf applied to that hole).

Another report that I found⁶ reported that Mycorrhizae concentrations was increased with the use of MicroMax and Osmocote. The increase in mycorrhizae was about double with the MicroMax than without the MicroMax. One additional report⁷ showed that both mycorrhizae and plant mass was increased with the use of MicroMax and Osmocote.

Once again, all the above reports were with potting soils, and not our bonsai 'soil-less' soil. We all know that the conditions we try to grow our bonsai in pushes the limits of horticulture. I believe anything we can do to help the nutrient value of the soil is a definite improvement. If the MicroMax improves the nutrient uptake of the trees, the small cost is worth it.

As an aside, I found that Stone Lantern offers a soil (Hollow Creek Bonsai Soil) already treated with MicroMax.

(Endnotes)

1. MSDS – Scotts-Sierra Horticultural Products Co. Marysville, OH 43041 Dated 1995
   
2. Whitcomb, C.E., Plant Production in Containers II, Lacebark, Inc., Stillwater, OK, 2003, pg.510-513
   
3. Whitcomb, C.E., US Patent 4328025, Micronutrient Fertilizer, 1982
   
4. Browder, J.F., Sulfur Requirements of Container-grown Pin Oak and Japanese Maple, Masters Thesis, Virginia Polytechnic Institute, 2004
   
5. Altland, J.E. and Fain, G. B. Fertilizer Placement and Herbicide Rate Affect Weed Growth in Containers, SNA Research Conference Report, Vol 48, 2003
   
6. Corkidi, L, Allen, E.B., Merhaut, D, Et.Al., Effectiveness of Commercial Mycorrhizal Inoculants on the Growth of Liquidambar styaciflua in Plant Nursery Conditions, J. Environmental Horticulture, 23(2):72-76, June 2005
   
7. Carpio, L.A., Davies, Jr., F.T., and Arnold, M.A., Arbuscular Mycorrhizal Fungi, Organic and Inorganic Controlled-release Fertilizers, Journal American Society of Horticultural Science, 130(1):131-139, 2005