My Introduction to Bonsai and Bonsai Pots

View From Here


by Jack Wikle

Could It Be Your Water?

There is no need to read farther --- unless you are curious --- if you are one of those people whose bonsai consistently look healthy and grow well. On the other hand, reading more could be helpful if your trees fail to thrive in spite of your conscious effort to follow some old but good advice: water thoroughly and leach frequently to keep unwanted salts from accumulating in your bonsai soil. This is especially true if you keep seeing the common symptoms of what horticultural scientists know as low quality water: persistently weak green or yellow-green leaves with darker green veins often accompanied by scorched-looking leaf tips and burned leaf margins (most prominent toward the leaf's tip).

By definition, “pure water” is nothing but water. But, being the “universal solvent,” water available to us from lakes, waterways, wells, the local Water Department or even a rain barrel is never pure. Actually, the “load” of dissolved minerals and other substances found in water – even water acceptable for use in human consumption and plant irrigation -- is highly variable.

People dealing regularly with water quality commonly make a distinction between “surface water,” the runoff of rain into ponds, lakes and rivers, and “ground water,” which typically has seeped deep into the ground through many tons of soil and rock before emerging as spring water or being pumped back to the earth's surface from a well. The reason for this classification is that surface water is relatively “soft,” that is, low in dissolved mineral content. Ground water, on the other hand, having accumulated lots of dissolved minerals as it settled deep into the earth is “hard,” high in mineral content. Where available, surface water is almost always superior to ground water for plant irrigation purposes.

However we need to be aware that knowing your city's water source is a river or reservoir does not necessarily mean it will be as low in pH and mineral content as one might expect. We are told it is not uncommon for municipalities to add chemicals, typically calcium hydroxide, to surface water to raise its pH (make it less acid) as a way of minimizing corrosion of public and private plumbing. This addition makes water less satisfactory for plant use.

Technical publications directed to commercial growers of irrigated greenhouse and nursery crops make it very clear that water quality is a major factor in their success or failure. The standard recommendation is that a comprehensive horticultural water analysis should be done before settling on a growing site. Tables specifying recommended ranges for alkalinity, pH (not the same as alkalinity), soluble salts (usually measured by electrical conductivity), and six or seven specific elements can also be found in this literature. It is relatively common today for commercial growers stuck with low quality water to inject acid into it to make it better for plant use even though this adds significantly to their production costs.

The main point here is that water, even water satisfactory for kitchen use and bathing, varies greatly in pH and mineral content depending on its source. Good evidence of this is that water softeners are considered essential household equipment in some communities and not necessary in others.

Actually, I have theorized for some years that an unrecognized difference between those people whose experiments in growing bonsai are rewarding right from the beginning and those who struggle for awhile before giving up in frustration because “they don't have the touch,” may be the quality of their water. A related observation is that, while cautions against wetting the foliage of one's trees during the heat of midday to avoid burn are common in bonsai literature, many growers do this routinely with no damage. Again, it seems likely that this seeming contradiction is explained easily by differences in water quality.

So, what does one do if poor water quality is suspected? It would be hard to go wrong to begin by obtaining an analysis of your water. Those using water from a municipal supply will find this as easy as requesting a copy of their water analysis from the local Water Department. (The Federal Safe Drinking Water Act Amendments of 1996 require “providers” to make water analysis information available to their “customers.”) People who rely on their own wells or other private water sources, can learn where a horticultural water analysis can be obtained by contacting their local Agricultural Extension Service office. (Water Standards for Horticultural Use offered by Dr. John C. Peterson at the American Bonsai Society's 1990 Annual Symposium, can be found at the end of this article.)

Another way of evaluating the quality of your water for horticultural use is to obtain a package of radish seeds (radish seedlings are known to be sensitive to high salt concentrations and other water contaminants). Plant these seeds in a relative sterile growing medium in a number of containers. Then water some pots with your household water and others with distilled water or other mineral-free water. Noticeable differences in seed germination and seedling growth between treatments -- better germination and stronger growth in the mineral-free water – will be strong evidence that your household water is a significant problem.

Once you learn that your water is not good for growing plants, what are your options short of acid injection like the commercial growers do? Of course the amount of water needed for routine watering will be a major factor in deciding what might work for you. For a small number of plants the answer may be as simple as purchasing distilled water. If available in large enough quantity, water discharged from air conditioning equipment or water collected by a dehumidifier will also work very well.

And, even though not pure (we have all heard of acid rain), rain water will typically be far better for growing plants than mineral loaded water. With gutter, and downspout rigged to direct water into a container of some kind, it will be surprising how much water can be collected.

One simple water treatment remedy being used by a number of bonsai enthusiasts in parts of the country with very hard water is to routinely add white vinegar, a tablespoon or two per gallon, to the water used on their bonsai. Others have written of adding as much as a cup of vinegar per gallon of water and applying this as a monthly drench. Actually, a little experimenting with vinegar additions to your water may be all you need to do to learn more about its quality.

Another simple, though slow acting, remedy used some in commercial production is to treat plants with powdered sulfur either by scattering it over the soil surface or mixing it into the soil. One advantage in doing this is that it makes it fairly simple to treat consistently weak and off-color plants while ignoring those that seem to be fine without the extra attention. This dosage doesn't have to be too precise but a teaspoon of powdered sulfur per gallon of soil is a reasonable target rate for experimentation.

A more expensive but almost foolproof remedy recommended as cost effective by horticultural scientists is use of a reverse osmosis (RO) water treatment system. This equipment is now widely available. Actual costs vary depending on the volume of water required. (I know personally two very active bonsai growers who went through considerable frustration with ongoing foliage disfiguration and unexplained tree loss before they decided their problems had to be water related and had RO systems installed at their homes.)

To summarize, water varies greatly depending on its source. Unresolved problems with your bonsai may be the result of poor quality water for growing plants. Although having low quality water is unfortunate, there are remedies available. Clearly, there is little to be lost by investigating your options and the potential for improvement in your trees can be great.

Desirable Ranges for Problem Water Parameters

Distributed by Dr. John C. Peterson, June 29, 1990 at American Bonsai Society Symposium at Ohio State University :

• pH: 5.0 to 6.5
• Soluble Salts (Conductivity): 0 to l.5 mmhos per cm (1 mmho is equal to 1000 umhos)
• Calcium: 0 to 120 ppm (1 ppm is equal to 1 mg per liter)
• Magnesium: 0 to 24 ppm
• Sodium: 0 to 50 ppm
• Chloride: 0 to 140 ppm
• Boron: 0 to 0.8 ppm
• Fluoride: 0 to 1 ppm
• Sulfate: 0 to 240 ppm
• Alkalinity: 0 to 100 mg per liter CaCO 3

Jack Wikle

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