by Lee Squires

Club Soil Analysis

We had a good turnout for our soil mixing workshop in February, and those in attendance should have an ample supply of soil to complete their repotting tasks in the Spring. This year we decided to stick with a similar mix that we used last year; however, a smaller ratio of peat moss mix was used. We mixed:

2 parts SoilMaster Red (baked clay)
2 parts red lava rock
1 part Fafard 1-PV potting soil

As I explained at the meeting, this is a basic mix. As you repot, I recommend the following:

Other plants may need different ratios, and you will just need to check each plant’s basic soil requirements either in other written material or on line.

If you use our basic mix and amend it depending on what particular plant you are potting, you should have good growing results. If all plants have a different mix that drains differently, then all plants can be watered the same. You don’t have to water something one day and not the next because you used the same soil in all of your pots. This is especially good when you go on vacation and your daughter waters for you. She can water all plants the same. Or, if you have a watering system, the system doesn’t know that a pine needs less water than a maple. For example, the stomata (pores) in pine needles open and close depending on water availability. Also, gases are exchanged through the stomata. When temperatures hit 90 degrees the stomata close and try to conserve water and reduce the evapo-transpiration through the needles. This is why you may see moist soil in mid-summer with your pines. The pines are not letting water evaporate through the needles by closing down their stomata. The water stays in the soil and is available to the roots. If you have poorly draining soil, the roots will rot. This is why Dick Blayney has a great collection of "permanent bonsai" with artificial needles hot glued on them.

While reading the American Bonsai Society Journal Volume 43 Number 4 2009, I ran across an article on Regional Bonsai Care – Bonsai Soil by Doug Hawley and Tom McCormack. They got in depth into different soils for different regions of the country, and the article would be very helpful to new and old hobbyists alike. I recommend reading it and joining the ABS, of course. Doug and Tom interviewed 6 growers from around the country, and they all used different soil mixes, but many with the same ingredients.

I have always thought that you need real soil (baked clay), drainage material (lava rock, grit, perlite, pumice, etc.) and organic material (peat – not pine bark) in your basic mix. The soil component is necessary to add the cation exchange capacity to the mix. This enables the mix to hold nutrients for the root system.. The drainage material is used, of course, to avoid root rot and the organic matter is used to offer some acidity to the mix and help to mimic rotted leaves or other material in a plant’s native environment. All of these, I think, are necessary to create a happy root system for our trees without a whole lot of extra work. By this I mean, if only lava rock is used, the fertilizer is constantly washed out of the pot and plants suffer. You must constantly fertilize and water because there is nothing in the mix to hold either nutrients or water.

Many growers use the same mix on all plants. I do not believe in this cultural practice. Boon M., John Callaway’s mentor and teacher, for instance, uses the same ratio of ingredients on all plants. However, he uses different size particles for different plants. This requires a lot of sifting and grading of materials. Most of us growers do not have the time to sift 3 or 4 different size particle mixes. Of course, a full-time professional has the time. Matt Ouwinga, a maple grower from Illinois, uses straight baked clay, but he only grows maples. Roger Snipes, from Washington State, uses straight lava rock, and he has experienced chlorotic leaves (yellowing) on some of his plants. Everyone is different and they all have varying results, some positive, some negative. We need to try to keep it simple but professional.

When I took a soil science class at UK, I soon learned that soil is definitely a science and not a bunch of good 'ol boy Ag. majors stomping around a cornfield in a pair of galoshes. It was more chemistry than "dirt" and was actually a pretty tough class.

Your soil is the key to success in bonsai longevity, and our club mix offers the best of all ingredients and is a beneficial all around mix. The baked clay is hard, doesn't break down to mush and has a good cation exchange capacity. The lava rock is, well, just lava rock but shipped from Colorado on a new flatbed trailer. The Fafard Mix is not just plain peat moss. It has a pH range of 5.5 – 6.5 (perfect), contains Canadian sphagnum peat moss, (peat does not break down, or rot and compress like pine bark) it also contains perlite, vermiculite (heat expanded mica), starter nutrients, a wetting agent, and dolomitic limestone to help neutralize the mix and make nutrients more readily available to the roots. Perlite (the white stuff) is actually volcanic perlite rock that is heated to 1300 degrees where it pops like popped corn. It is not a plastic artificial ingredient. The hundreds of pore spaces hold nutrients and water but also afford great drainage for the mix. If you don’t like the appearance of a few white chunks, top off your potted tree with a ¼“ layer of baked clay for a uniform soil surface. This peat mix, along with the proper ratios of the other two ingredients, puts the “science” into our soil mix.

Whether you win or lose, bonsai is a daily battle of us against the elements, and the best soil is needed to help wage the war and make us victorious.