Garden water pH

I just realized that our municipal water has a pH of 9 when tested at the plant. Should I be doing something to correct the pH when I water my bonsai? I have 21 plants and it would be a real pain to have to correct the pH of the water every day. Am I just being overly fussy?

Yes, 9 is very alkaline and is likely to slowly lower the health of your trees. Either use collected rainwater, adjust the pH with citric or acetic acid via a siphon system (or manually in a can) or fit a reverse osmosis unit (expensive, but very effective)

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pH 9 is extremely alkaline, it severely impacts the ability of plants to uptake iron in particular that then affects the ability of the plant to synthesize chlorophyll. Take a look at this chart - it is the original chart on the subject and you can read the original article too.

  1. Pettinger, N. A. A Useful Chart for Teaching the Relation of Soil Reaction to the Availability of Plant Nutrients to Crops. Va. Agr. Ext. Bul. 136, 1–19 (1935).

Some ppl use vinegar as well. I’ve been meaning to look into that, but I’ve only drained my rain barrel once so far this season. It looks like I’m about to drain it again though, so it’s time to figure out a plan B.

Hi @Forestcat,
I have been correcting my ph with vinegar since January. My pines were yellowing which prompted me to buy a ph tester and see what’s coming out of the tap. Most of the time it’s around 8. At best I get about 7.2, at worst just under 9.
Using a 5 gal bucket to mix up my correction water I generally mix up 1-2 gallons. Seems like it takes about 4-5 tablespoons of vinegar to get the water down to 4. The siphon is a 16/1 ratio and I end up with 6.5 at the end of the hose.
To make the process a little quicker I attached quick release fittings to the mixer, the hose bib, and the hose.
I have had a few issues with this method.

  1. The siphons sometime malfunction. Water will flow out the siphon tube, diluting the correction water.
  2. Cannot use the siphon with my preferred watering wand as it restricts the water flow too much. This issue has been addressed in some other threads.
  3. I do use the same method to apply fish emulsion and sometimes the siphon clogs.

Is this per gallon? Do you use plain distilled vinegar?

I’m kind of guessing I use 4-5 tablespoons per gallon. I just put a glug of vinegar in and then check that the pH is right around 4 to 4.1, maybe 4.2
And yes I just use regular distilled white vinegar. You can also use muriatic acid which per gallon would only require maybe 1 teaspoon, but I have two kids I don’t really wanna be messing with something that harsh on a daily basis.

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my understanding is that vinegar won’t last as long so if you take a while to use up the water the ph might have gone up, something to keep in mind. and yeah, be careful with the muriatic acid, i wore a mask and still got lightheaded and not in a good way. i’ve also had the siphons malfunction and blow rather than suck, so check up on them!

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I have not found that there is a drastic ph spike when using vinegar. There is a little rise in ph over several, but then you can just add more vinegar.

I always aim for around 5 Ph. It’s more friendly to azaleas which only require a Ph of 4.5 -6. Rainwater in the UK averages between 5 to 6.

I spotted this information online:

The pH (not PH) scale is used to measure the acidity or alkalinity of an aqueous solution and is determined by the hydrogen ion content (H+). This scale was invented by a Danish scientist called Sorenson in 1909. The pH scale ranges from 0, which is strongly acid, to 14 which is strongly alkaline, the scale point 7 being neutral. Examples of solutions with differing pH values include car battery acid (pH 1), lemon juice (pH 2), beer (pH 4), natural rain (pH 5-6), milk (pH 6), washing-up liquid (pH 7), seawater (pH 8), milk of magnesia (pH 10) and ammonia (pH 12),

The pH scale is logarithmic rather than linear, and so there is a ten fold increase in acidity with each pH unit, such that rainfall with pH 5 is ten times more acidic than pH 6, rainfall with pH 4 is 100 times more acidic than pH 6 and rainfall with pH 3 is 1000 times more acidic than pH 6.

Rainfall acidity is measured in pH units. �Normal� or �unpolluted� rainfall has a pH of 5.6. This is slightly acidic due to the presence of carbon dioxide in the atmosphere which forms weak carbonic acid in water. It is not uncommon for acidified rainwater to have a pH of 4, about 30 times as acidic as normal rainwater.

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If your pH is 9 adjusting it will definitely behoove your trees. Their are many acids you can add to alter the pH into a lower register. I too have found additions of acetic acid to rise back up after 24+hrs. Other acids such as muriatic or phosphoric seems to be less fugitive but still require monitoring. Think about what you use and what it contributes when dissociated such as phosphorus, sulfur, nitrogen, etc. The most successful results I have seen are people who have purchased a reservoir that they then mix up a week or more worth of water for their trees and adjust the pH at that time. This seems to be a reasonable work load for most and I have seen collections 360 back to health after this alteration. You will need an accurate hand pH meter to check your reservoir over the days and until you develop a protocol for you specific water. One more note is that some municipal water will have pH fluctuations over the course of a year so always keep checking with a meter. Hope this helps…


Thanks, everyone, for your good advice. Now, does anyone have a recommendation for a pH tester? Strips or gadget?

I’ve been using a test kit that I have leftover from my aquarium days. I’d love to move to a meter though as that’ll be infinitely easier.

Gadget… Don’t go with the cheapest or most expensive (lab grade…). Try to find one with a ‘calibrate’ function.
A ‘dissolved solids’ function might be useful, dissolved oxygen—not so much. $50 range. If it is calabratable, find a 4pH solution to use for that; also, maybe a 7 and a 10 if you are a serious geek. They WILL come with instructions.
pH papers get you into the ballpark +/- 0.5 or so, depending if you can read the paper, and, if your liquid is colored or high in dissolved solids… There are multi-segmented pH papers with several small different colored segments that will give a better read. Buy one pack. You will never use a case. They are cheaper and easier to use; but, less accurate.


One more bit of info, coming from an aquarium keeping background, PH is tied to KH (also called carbonate hardness, or total alkalinity or buffering capacity) you can get an aquarium test kit for this too. The effect of KH on PH is this: the higher your KH, the harder it will be to lower the PH, but also you might get “bounce back”, the PH rises again because the KH is buffering the water. The lower your KH the EASIER it is to lower the PH with acids, and it will stay low. If you have high KH the easiest thing to do is mix it with rain water before you add acid, or see if just blending with rainwater and waiting a couple days will lower the ph. or go with straight rainwater if that is possible. I am going to buy a rainbarrel kit because I have high KH. (great for the koi pond though)

Good to know! I have a $19 one in my cart that does not have a calibrate function. I’ll keep looking.

I ended up ordering Aquarium testing strips. Turns out the water is at 9, but the filtered kitchen water is at 7. Unfortunately, I wasn’t paying attention and the strips I got only go down to 6. Now, I add 1-2 TBL of vinegar to 1 gallon of water. The trees seem to be doing better and I’m getting some moss growing again.

Hay Maryann. Good.
As per Rafi`s chart; above 8.0 pH, plants will slowly starve of vital nutrients. The can’t uptake iron, potassium, manganese, or nitrates. Only genetically acclimated plants will survive in the alkali flats, and they do poorley.
Just for my head, what are you using in your kitchen to change the pH? A simple particulate water filter would have no effect.
Oh, ya, get another set of pH papers for 4 to 8 range. Will be safer for your plants… Use both… once the pH is close or below 6, the first paper will not change… You could overshoot , and never see it.
There are pH plastic strips with three different pads of different color changes. Gives a easier to read and more accurate range. Look for the chemistry / lab grade.

I like to think this isn’t rocket science; however, I will take any help I can find!
Bonsai On!

A little late to the party, but I have been using this digital pH Meter with calibration to nail down my pH to 6.2 and I have noticed a huge difference when combining this with Biogold. My trees have never looked more green and full of buds since this is my second season using this method.

PH Meter -

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