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.)

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  1. José Rivera says:

    Good information, thank

  2. Vern Maddox says:

    Great bit of information and one that most of us don’t consider. Is the muriatic acid you use the concentration used for swimming pool pH adjustment? I think the acid used by brick/stone masons may be a higher concentration, but I’m not sure. I guess the point is to check the mixture before watering with it. Thanks for another helpful blog.

    • crataegus says:

      I really don’t know if it’s the same as the swimming pool concentration…but as you say the important thing is we check the pH out of the hose.

  3. yenling29 says:

    Greatly appreciate tips like this and all the wonderful ones on your blog! I was wondering- before each time you water is it necessary to mix the water and muriatic acid up? Also where do you get your muriatic acid? Would love to hear a future post on water hardness as it relates to Bonsai.

    • crataegus says:

      You can get muriatic acid from Lowes or a similar store.
      It saves time to mix up a larger container. Mine is about 25 gallons and that takes me through several waterings for my good-sized garden. The Hozon siphon is a 1:16 siphon, so with 5 gallons of acid dilution you’ll get 80 gallons of adjusted hose water to water with.

  4. Or?? You just use akadama as main ingredient in your soil. It will buffer your moisture to aprox Ph 6.0 and your Us to 150 – 100. That is if your water has a consitancy between ph 7.8 and ph 6.5.
    Akadama: most of your bonsai will love it.

  5. carterbeall says:

    I have heard that the water in my area is very alkaline; near pH 10, but my trees all seem happy. Do I need to rush to adjust my water?

    • crataegus says:

      Definitely test the water, don’t take rumors to be what it is. It’s good your trees look happy. Still, they’d probably appreciate a pH shift, and it’s not a thing to worry about rushing. Any change in pH usually will take a long while to show up in the trees anyhow.

  6. Sage Smith says:

    Excellent post my friend!!!!!!!!! Water ph is something that most people don’t think is a problem. Water is what we give our bonsai more than anything and the ph should be correct for our tree. Thank you for what you do for the bonsai community. You are always trying to better our trees.

  7. Joseph Cachia says:

    Hola Crataegus  Bonsai,Thanks for  a very informative and  equally interesting article on the value of correct pH for watering our Bonsais.  Will certainly tke your advice.  Living in a “limestone Based Island, ie Malta, our value will surely be above 7. Congrats and best regards !Jo. F. Cachia

  8. A great post very informative.sometimes we don’t think about the water we are giving our trees.I give my trees only collected rain water,more work but the trees are much happier.

    • crataegus says:

      Rain water can be great! I used that down in the mountains of Arizona, when I had a very small collection. I saved the water in barrels from my roof, and nearly got through the dry spells without ever using well water.

  9. jem976 says:

    Is it advisable to put Kanuma in juniper and pine soil mixes?

    • crataegus says:

      Akadama is best, Kanuma holds more moisture, which the conifers won’t like much. In Japan the akadama percentage is about 65%. It’s pretty expensive here, so you might try a lower % of about 33, like in a Boon’s mix.

  10. endsurg says:

    Hi, Mike, great post. I never really thought about the affect of pH on our trees but it really makes sense. I tested my water with a fish tank tester and, lo and behold, it was alkaline (7.5). I do use 33% akadama (so maybe that’s why I haven’t noticed a yellowing) so what concentration of the muriatic acid do I use? Why does it take so long for there to be a noticeable change in the trees? Two years seems an awfully long time. Also, would acid loving trees like azaleas need an even lower pH? Instead of 6-6.5, would you want the pH to be 4.5-6.0? When repotting azaleas, if I use 100% kanuma, should the new soil be made to have a 4.5-6.0 pH? Wow, this turned out to be a soliloquy, sorry but the proverbial “can of worms” was opened. Speaking of worms, should we…….(ha,ha, not going there).

    • crataegus says:

      It’s hard to green up old conifer foliage. Much easier to do it in the springtime when it’s growing, by giving the right conditions. Conifers in general are slower to respond to changes in their environment, but most trees shift slower than we’d like.
      It is true azaleas like even more acid than most plants, but you can grow an azalea very well with your water adjusted to 6-6.5. If you’re using kanuma, the soil will be even more acidic, so they will be happy.
      In a five gallon bucket, you would need to add about .25 oz. muriatic. Then that is siphoned into your hose, but the main thing to worry about is the pH coming out of the end of the hose. If you use this technique, check the pH frequently until familiar with it. Don’t want to make a mistake!

  11. Jim Troyer says:

    Interesting post. Can you use vinegar?

    • crataegus says:

      You can, but don’t let it sit long. The vinegar has a faster pH bounce, so your pH will go up if water is left to sit.

      • Todd Morgan says:

        I started putting vinegar in my watering can, adjusted to a pH of around 6.5. let them sit in the watering cans for a day, and it was back up to 7.5… does that mean the any water still in the bonsai soil the next day will not be acidic, either?
        I guess I need to try muriatic acid for a longer lasting acidic environment in the pots…

      • crataegus says:

        Yes, good observation. A student in one of my Seasonal classes was an aquarist, and said that vinegar gives a faster pH bump than muriatic. He thought it may have to do with the bacteria eating the acid. It does seem to rise a bit no matter what you do, but muriatic is slower to do so. As for what the soil pH does with it once watered, that is a very good thought and I don’t know really, I assume it is similar to the water but that’s just a guess. What soil one has will make a difference. They do make soil pH testers, too.

  12. Ken Krogholm says:

    Great post Michael! How would symptoms be on spruce and scots pines if using very hard water with a pH around 8? Yellowing of only the new shoots or the whole tree? (substrate is Pumice)

    • crataegus says:

      Yellowing or lightening of the foliage might be seen over time if watered with pH of 8. Both new and old foliage may be affected. When you change pH also keep up some moderate fertilizing, which will help green things up. You may find that older needles will be reluctant to change color much. Sometimes it takes a couple years to see a major change.

      • Ken Krogholm says:

        So assuming alkaline pH (around pH 8) is causing Fe deficiency in my pines and the needles from this season are pale and yellow (but not the older needles) would you still assume a long response time in greening up the new needles if I manage to lower the pH and thereby make the Fe in the pots readily available for the plants? Would foliar feeding speed things up?
        Thanks for sharing your knowledge!

      • crataegus says:

        Do try that. If you were to change the pH you might see greening up this year. It’s hard to green up old needles, but this year’s needles might still green up a touch. Next year while they are growing is when we can make major strides in color.

        As a side note to anyone else reading this, I don’t recommend using iron chelate since what that is is essentially a bandaid to a water problem. When we change the pH we get many more benefits than just iron availability.

  13. Terry Bryan says:

    Hi Michael,
    I have a J White Pine and Shimpaku. My PH as tested by my local municipal averages 8.6-9.5. My J white pine seems fine, but the Juniper seems grey, not as green as it should be and I’m losing some tufts that brown and die off. Could this be related to the PH or over watering? I replanted the plant this spring in 60% akadama mix(Japanese Mix called Dragon Spring all Japanese components) and it’s been struggling since. All of my plants are either in a boons type mix or this Japanese mix. I just watched Ryan Neils video on watering and freaked out when I found out what my PH really is, he gave a shot out to your water injection system, so I thought I’d check it out. Thanks for all you do for Bonsai.

    • crataegus says:

      Glad you watched Ryan’s video on watering—
      It’s surprising that your white pine is doing well and the juniper is not, for me that suggests something else is wrong with the juniper. But I would begin by changing the water as any pH that high is a stressor for almost any tree we work with for bonsai.
      If your white pine is on black pine root stock, a grafted tree, then that might be the reason it isn’t affected much by the pH. But it will do better at 6.5.
      Remember that every 1.0 percent rise is 10x higher pH…so a 2.0 rise is 100x change in pH! from 7 to 9 is 100x difference. That is really significant for biotic life of the soil as well as the plant itself.

      • Terry Bryan says:

        Hi Michael, Thank you for providing more info. The white pine is a graft and I think I figured out that I was overwatering the shimpaku. So, I’m watering it less frequently and have it on an angle so it drains very well after. I need to get my PH under control soon. I also read that using MIcromax with micro nutrients can help with high PH. I’ve ordered a PH kit so I can get a base line and go from there. There is so much to learn!
        T Bryan

  14. Scott says:

    Hey Michael,

    Great post. I remember reading this last year and immediately picking up a pH and water hardness tester. Unfortunately, I didn’t make it much further then that in improving my city water.

    I recently purchased some decent shohin with well established moss. In the last 2 weeks, the moss has declined sharply. I live in the city so I’m sure it most likely its heavy in salts and heavy metals. Have you used, or would you advise in using, a garden hose attached water filter?

    • crataegus says:

      I have not used such a filter. It looks like it only takes out chlorine and chloramine, which are not in themselves damaging to the tree roots. Getting rid of the salts will take a reverse osmosis system.

  15. Troy Baggerman says:

    Hi Michael,
    Great post! I live in Beaverton, OR, and have been using our city water source for my trees. It smells of chlorine (1.1 mg/L) and has a Ph around 8. I just set up a system like you described here (using muriatic acid) with the added step of letting my water sit overnight to off gas chlorine. I have 2 questions:

    1) I have noticed my Ph rebounds towards 8 over a few days. Do you have that problem or a solution?
    2) Do you know if using muriatic acid (hydroCHLORIC acid) adds chlorine to the water solution? Should I even be worried about chlorine, or how much is too much?

    Also, I just saw your Mountain Hemlock forest planting at the Pacific Bonsai Museum. What an inspiration! I have seen pictures , but it is so much more impressive in person.

    Thanks for all your posts,

    • crataegus says:

      The pH bounce is a familiar issue. I’ve heard a few different reasons for it, bacteria eating the acid being one of them. Try to use your water within a few days and it should be ok.
      I don’t know if chlorine is an issue with muriatic. Most municipalities add some to the water, if you live in Beaverton I don’t think it’s enough to be a problem. Other areas have very high chlorine. I’m no expert in how much would be a problem though, from what I’ve seen hardness and pH are more severe inhibitors of plant growth if we get the wrong.
      Glad you liked the hemlock! Great exhibit, lots of cool work there from a lot of different folks-

  16. Josh Bentley says:

    I’m finally adapting to this method for pH reasons. Do you know if it’s possible to add fertilizer at the same time as the acid? Will the acid denature the fertilizer?
    I heard some about your fertilizing practices from the podcast Andrew did on asymmetry, but this was not covered.

    • crataegus says:

      Yes you can add acid to the fertilizer with the injection systems. Many of the fertilizers will bring down the pH quite a bit by themselves. I guess the answer is just to keep testing, with whatever changes we make. Sort of fun, if you’re a chemistry nut and had some of those explosive kits as a kid.

  17. Matt Spain says:

    Hi Michael,

    Thank you for this! Here in San Jose, our water is notoriously bad for bonsai because it is both high pH and hard. I have toyed with the idea of RO, but it’s tough to get over the waste and the cost, so I am intrigued by this system. Is the diluted acid solution dangerous to touch or drink out of the tank prior to mixing with the tap water? I ask because I share my garden with my kids and dogs. Also, does this system change the flow rate of the water? I am considering coupling it with a basic carbon filter, which does slow the flow rate. And last but not least, have you found that pH is a more or less important variable for healthy trees than water hardness?

    Thank you!


    • crataegus says:

      Hi Matt!
      No, there’s usually no danger in the diluted acid solution. Ours is something around the range of vinegar when it gets drawn into the hose. Yes, it can lower the flow rate. I think pH is the first variable to worry about, secondarily hardness.

      • Matt Spain says:

        Michael, thank you! I was feeling a little bad about hitting you up so hard on a post that’s going on a decade, and I greatly appreciate your commitment to your readers.


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