One Essential to Plant Health: Water pH
Have your trees been a bit yellow? Seem stressed out? It may be time to check your water pH.
When our bonsai are watered with an acceptable pH, one variable to plant stress is removed. Mineral deficiencies (high pH) and toxicities (low pH) will be averted in that acceptable range. Any kind of water source, whether it is a well or a municipal source, should be checked occasionally for pH. Some municipal water sources in particular can range greatly over the year, from the low 6’s to over 8 in the summer.
- Naturally we might think neutral is best, a pH of 7. And it’s not bad, you can grow plants in that. But actually the widest range of plants can be grown in slightly acidic pH, so a pH of 6-6.5 is ideal.
- A pH of 8 is 10 times more alkaline than pH 7, so a bit of accuracy here is a good thing.
- Once we get higher in the alkaline range, above 7.5, we limit the solubility, and therefore uptake, of fertilizer. Phosphorus in particular is one of the least soluble, but is at its most accessible to plants at pH 6.5
Testing pH is best with a freshwater pH kit, which uses drops, found at a pet store and used for testing pH in fish tanks. An electronic reader is another option. Avoid litmus paper. It’s not accurate enough.
This shows a pH kit from a pet store…fill water to the white line, add three drops of test solution, cap it, and then shake. This test came out just about right for our bonsai—about pH 6.3. A pH of 6-6.5 is ideal.
OK then, enough of the warm up to the subject…
- How then do we adjust the pH coming out of our hoses to get the best bonsai health that we can?
The easiest is to use a siphon for a small or modest bonsai yard. Fertilizer siphons can be used to inject a diluted acid (muriatic mixed with water is best) into the hose. The skinny siphon hoselet goes into the bucket of diluted acid, and is drawn into the hose near the bib. Then the acid injection mixes in the hose as you water. With a bit of adjusting how much acid per gallon of concentrate you have, it is easy to water with a consistent pH coming out of the hose.
The snaky black hose is a siphon, that draws a mix of water and acid up and into the red watering hose—with a bit of experimentation, it’s easy to get predictable pH coming out of the hose to water bonsai with. (This one is a brass Hozon siphon, seems to work better than the plastic ones.) Most horticulturists tend to avoid muriatic acid, as the potential for chorine burn is there; another option is acetic acid. If you use muriatic, use an open tank so chorine gas can escape, or use acetic acid dilution within a day or two (bacteria tend to eat it which can cause a pH bounce).
For instance, say we have a five gallon bucket of tap water at about 7.8 pH. If we add about 0.5 oz muriatic acid to this five gallons, and siphon it into our hose, it will come out of that hose at about 6-6.5 pH, perfect for our bonsai.
- The siphon works on draw. Be sure to have the water volume of your wand on a set setting, or the pH will change. In other words, if we have a ball valve and we water with less that full open, it will be a different pH than if we have the cock open full. I have a very soft wand and water with it full open, and leave it there, so the pH does not vary at all.
- This does assume that most of you will have water that is, if anything, too alkaline. For water that is too acidic, add baking soda to the bucket in a similar experiment until the right pH comes out of the hose.
And then…be patient!
- You will not see an immediate shift to greener, happier plants. Conifers in particular may take two years before they look significantly better. So a bit of faith in the process is a good thing. Stay consistent.
Hardness of water is a separate issue…but adjusting the pH will take care of one of the major water issues one might have.
(Be sure you don’t get muriatic acid on your skin, but if you do, washing it off immediately will do the trick.)